A PRELIMINARY STUDY OF THE

mnmon LEAST TERN
(STERNA ‘AALBIFRONS

ATHALASSOS BURLEIGH AND LOWERY)

Thesis for thb Dam of M. S.
MICHIGAN STATE COLLEGE
John'William Hardy

1954

 

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By

Jonn William garuy

Submitted to tne Scnool of Grauuate Studies of fiicnigan

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Deecription.......................
THE 33223233 CYCLE...................
Arrivél in thé Nesting Area.......
Courtship.........................
Aerial f1i;ht..................
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copul{3'tion.....................
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Distributimi of the bir‘fs in true terneljf........................J3
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COHPTriSOD With other térn N9°t3.............o.....o....o.......53
Initiation of neat-building.....................................50
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Activities during incubation....................................7
Hatching...........................................................?2
Growth and Development.............................................72

Katal down stage................................................?5

Pre—flying juvenal stage........................................74

Flying juficnal stage............................................75

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Page

An interior least tern attempting t6 reacn n>r eggs
t rougn a wire trap placed over txe nest...............8

Susner listriouticn of tag ilterior least tern........13
Prooeole ,iLratian routes of t-e interior least tern..lu
Sunmer distrioution recorls of tge interior least tern.20
A typical scream at graee level........................jl

A Strealn at Eyf"‘0r:“r:! gr‘ét't‘le 1:3le I 0 o o o o I o a o O o 0 o o o o e o I O .:”}l

 

A typical arll :leils streau............,,,,,,,,.......33

AI}. iJLlatUI-e Strealn.........n..o........o...............:§2

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Tennessee, and massing time of tne interior la st tern.

(adaptel Iron Genier, 1330)............................33

Relatinn Decween neignt of Mississippi River at memunis,

orrelatien of water levels witA neszing of CH» interior
loest tern at Bell Island in tee Ohio River in summer
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Tge teenerature-numiaity relati‘ns;ip in tne Bell Isle d
region............IOCOOCCOOOOI.-aIo.....................39

Rainfall and wind COnQitions in tle Bell Islanu region,flo
Tue mainstream siae or tue bar........................,44
Looking upstream over tee broad exnanse of tee oar.....44
Bell Island............................................45

Suaued areas of tne our are gravel accumulations on waica
LAOSt OI. tl-e terns. n‘SUS Wpre locatedOOO'l00.00.00.000055

Diagran of tue nest distributiwn of tne interior least
tern onBell ISlankloooooOoo-ooooooooooooccaoooc-o-oool.E:b

A typical interior least tern nest at Bell Island......bO

A nest of tne interior least tern at Bell Island.......b0

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Fifi. 20. Records of attentive ani inattentive perioas at two
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Fig. 24. A two-ca; old inteiior least tern CLiCK at Bell Islaid.77
“ig. 25. Turee interior least tern ciicxs from tue sage nest....77

.A two-week olu interior least tern cnick (estitatea ass)
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Fig. 27. Daily weiggt increase of interior leasa. tern c :icks....78
Fig. 25. A racord of attentiveness and brooding.................83

Fig. 29. A sen arounu a tern nest cmnfines tie CuleS so Enac
tileyf Cfln De St1idifaQOOOOOOoooo.0.00.00cocoons-oaoooooooogb

Fig. 30. A feuale luterior leasn tern alignting at ner nast at
Bell ISlalluooooococooooooooooooooooooooooo...onooooo.oogb

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HTRODUCTION

Perhaps the most challenging issue facing the author preliminary to
launching this study was the desire to select a relatively "unexplored"
tOpic. In addition, because of other duties it was necessary to select
for study a species which nested comparatively late in the season. The

interior least tern (Sterne albifrons athalassoe Burleigh and Lowery)

 

was, thus, an apprOpriate choice, since its habits were not well known,
and it is characteristically a late breeder, usually not beginning the
nestin season until mid-June or afterwards.
Although much has been written concerning the life histories of terns,
prOportionally few extensive studies have been conducted on the least
tern. Cf the larger studies, only the work of the Marples (1934) on
British terns (dealing primarily with the common tern) contains extensive
data on the least tern. The other investigations are far over-balanced
in favor of a few of the larger more common species. This may be par-
tially explained by the fact that the least tern colonies are smaller
in comparison to ternerie: of other species. In addition, the nests
are usually well scattered within the breeding grounds so that study of
a large group of birds from one blind is not nearly so practicable.
The literature on the least tern consists primarily of short articles.
The most notable of these include the studies of Hagar (1957) on the

\

least tern of tnc Atlantic coast 0

f Massachusetts, the sunmary by Bent
(1947), the investigations of Ganier (1930) on the Mississippi River in
Tennessee, and the work of Stiles (1959) with birds of the Missouri
River in Iowa. The articles by Ganior and Stiles represent the most ex-

tensive studies of the interior subspecies, since both present information

on the principle phases in the life history. With a few exceptions,

viz., the investigations of Maser (1940) and Youngworth (1953), the re—
maining published information on the inland birds consists of short
notes, principally on migration with occasional references to observa—
tions of breeding.

The present investigation Hes divided into three parts: (1) an actual
field study of a colony of interior least terns at Bell Island in the
Ohio River from June 20 to early ertcmber, 1953; (2) an analysis of
available information in published literature; and (5) correspondence
with ornithologists throughout the range of the subspecies. The latter
in particular aided in supplementing published data, in gaining the most
recent infornation on the birds, and in presenting as well rounded a

picture of the interior least tern as was possible in the limited time.

AC "COE'LEDGEI-IENTS

The writer wishes to express his sincere thanks to Dr. George J.
Wallace, who supervised this study and whose constant guidance in the
preparation of the manuscript has been of great help. Grateful acknow-
ledgement is also due to Richard Brewer and Kenneth Stewart of Southern
Illinois University who assisted the observer in much of his field work,
to Dr. S. G. Bergquist for assistance in preparation of the section on
sandbar formation, and to Dr. C. L. Gilly and Dr. R. H. Manville for
suggestions in preparing the final manuscript.

The writer also wishes to express deep gratitude to the following
persons who, through personal correspondence with the author or with
Richard Brewer, provided a wealth of unpublished data on the interior
least tern that would have otherwise been unavailable: Richard Anderson,
St. Louis, Missouri; Frank Baumgartner, Oklahoma A. & M. College; Ben B.
Coffey Jr., Memphis, Tennessee; James E. Comfort, St. Louis, dissouri;
Miss Doris Gates, North Platte, Nebraska; Karl H. Maslowski, Cincinnati,
Ohio; Robert M. Mengel, University of Kansas; Burt L. Monroe, Anchorage,
Kentucky; Russell Mumford, Cortland, Indiana; H. R. Smith, Evanston,
Illinois; I. G. Vaiden, Rosedale, Mississippi; Dr. Gordon Wilson, Western
Kentucky State Teacher's College; Dr. Ray 8. Wycoff, Lexington, Nebraska;

and William Youngworth, Sioux City, Iowa.

-h-

TAXI‘ SKY OF THE NORTH AMERICAN EaST TERHS

The family Laridae is one of the 16 living families of the order
Charadriiformes. It comprises 85 species and 185 subspecies and contains
two subfamilies, Larinae, the gulls, and Sterninae, the terns, both
world-wide in distribution. The great majority of the Sterninae are
inhabitants of coast: 1 areas of the seas; however, a few species occur

on the larger fresh-water lakes and st sans.

The least tern (Sterne albifrons) is divided into 9 subspecies by

 

Peters (19§#), but two new Mezzican races and the interior race athalassos

 

have been described since that time. The species is found throughout
most of the world in temperate an" tropical re gions, along the coasts
and in the interior. The nominate race albifrons is found in western

Asia and EurOpe south to the Mediterranean Sea. Of the five North Ameri—

can forms three occur in the United States. The are antillerum,

 

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least during the breeding season.

In early taxonomic studies th e breedizg least terns of the Mississippi
River and its tributary streams were considered identical to those of the
coastal waters of the United St: :tes. Mearns (1916) separated the Cali-
fornia Pacific coast birds as a new race browni. Oberholser (1953)
assigned Specimens from northern and central Louisiana to that race, even
though this presented the unusual case of two populations of a subspecies
separated by over a thousand miles of land area.

In 19h2 Burleigh and Lowery described a new race of the least tern
from the interior United States based on specimens collected in Louisiana

and additional mate rial from th e Mississippi and its tributaries to th

north. They designated it Sterne albifrons athalsssos, the interior

 

‘

least tern. t su‘ osedl differs from antillerum tne Atlantic and Gulf
PP Y ,

 

coast race, in the much darker coloration of the upperpcrts, and in having
little distinction between the color of the back and the hind neck.

It is the opinion among some workers that the diagnostic features of
the three northern races of this tern are much too superficial and
variable to warrant their taxonomic separation. Such characteristics as
number of black primaries, used to separate browni of the Pacific coas
and black on the bill, used to separate staebleri of Mexico, are known
to exhibit such variation in all races. The black tip on the bill in
particular seems to vary much with the season of the year in all races,
being prominent during the breeding period and fading greatly by autumn.

Regardless of the problems involved in the taxonomy of these subspecies

and the possibility that athalassos may not actually be a valid race, the

 

fact remains that ecologically at any rate, the interior bird is dis-p
tinctly different from the other North American subspecies. It is hoped
that this study of the habits and environmental requirements of the
interior least tern will reveal some information bearing on the validity

of the race.

METHODS OF STUDY

Field work on the interior least tern consisted primarily of direct
observation of selected groups of nests within the colony from a blind.
The selection of a few nests rather than a large number was the only
method practicable, since least tern nests are characteristically widely
scattered within the boundaries of the ternery. Th blind was first
placed within a semi-circle of seven nests, and later moved to a second
group of three. These were the most closely observed birds from which
most of the data on breeding habits were taken. Tern nests to be
studied were marked with small stakes and each assigned a letter 80 that
it might be easily referred to in the notes.

The drOp trap method of capturing common terns described by Palmer
(19Ql) and Austin (1958) was not successful with the least tern. In al-
most every case the alarmed bird scurried under the edge of the trap
before taking flight. One individual alighted on top of it and tried to
reach the eggs by pecking at the wire (see Figure 1). Continued attempts
at trapping caused the birds to become so wary that it was feared the
normal routine of the ternery might be seriously disrupted. Austin
(1954, 1947) eXperienced similar difficulties with common terns. Often
birds would not return to the nest until the trap was removed. In the
present study only one tern was captured by this method. The beginning
of hatching, which greatly decreases he efficiency of trapping, ince
the young are precocial, necessitated termination of these activities.

The value of marking adults in this study would have been to observe
the roles of the parents in nesting duties. Some such data were taken
from observations of the one marked bird and its mate and from careful

watching of other terns. Behavior traits when used with caution, were

useful in separation of males and females.

Frequently birds and nests other than those specifically under obser-
vation provided pertinent data. Thus, a general watch was kept over the
whole colony from the blind and by walking through the ternary.

It had been planned to collect a limited number of Specimens, but
delay in securing permits prevented this.

Young terns were color banded so that their individual records could
be kept. Heights were taken with a gLam scale, accurate to the nearest
gram. Measurements were taken in millimeters of total length, culmen,
and wing. As feathers began to emerge their growth was also measured.
Notes were kept on progression of the plumage.

Information on food habits was gathered by stomach analysis, observa-
tion of occasional discarded fish, and seining of the littoral waters.

The island and the ternery were mapped, and general records were kept
on weather conditions, including temperature, wind direction, and
velocity, the latter by estimate. Data on rainfall and river stages
were secured from the official state observer at Shawneetown, Illinois,
and from the United States Weather Bureau at Evansville, Indiana.

The extensive personal correspondence with many ornithologists
throughout the Mississippi River Valley and adjoining areas was begun
in early October, 1955, after completion of the field work. Through

this method much information on variations in migration, environmental

conditions, and breeding habits was made available.

 

Figure 1. An interior least tern automating to reacn ner
egas tflr0313 a ere trap placed ovwr tie nest.

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General Range

The interior least tern ranges in summer from Baton Rouge, Louisiana,
north along the Mississippi River and its main tributaries, the Ohio and
Missouri, to southeastern Indiana, central Kissouri, southeastern South
Dakota, southeastern Wyoming, western Kansas, and western Oklanoma (pan-
handle area). Formerly, at least it occurred north in the Mississippi
River Valley to northcentral Iowa, and rarely to eastern Iowa (Dubuque)
and on the Missouri River system to Montana.

A more detailed account of its distribution is presented in the
following discussion.

Spring Migration

Least terns appear in migration in large numbers along the Gulf coast
of Louisiana in late April and early May. By the third wees in April,
the interior form has begun migration up the Mississippi River. Ganier
(1950) considers the species common and well distributed in migration at
Vicksburg, Mississippi, occurring in flocks of from 50 to 60 birds, which
feed along the sloughs and the river. According to Mabbett (l393) birds

\ 5'

first arrive at Rodney, Mississippi, between May 6 and 15. Vaiden 1 has

observed least terns at Rosedale, Mississippi, as early as April 25 (1927),
April 27 (1948), and May 8 (1954), but states that it is usually after
May 10 when the first birds are noted.

Kigration also occurs up the Red River at least as far as Shreveport

in northwestern Louisiana, but for some reason seems to be much delayed

 

1

'I

Citin5 0: an authority without bibli05raphic reference means :ata wake

obtained by personal correspondence.

-13-

compared to movement up the main stream route. Jeter has observed least
terns at this locality for several years and has never recorded their
arrival before May 6 (1951, 4 birds). The following data depict the
migration of the least tern at Wallace Dam on the Red River south of
Shreveport as recorded by Jeter.

$7

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Kay 50 O
* one bird was seen north of the city on May 10.

Terns have been reported by April 30 (1939) ne'r Bowling Green, Ken-
tucky (Jilson), but th main migration apparently takes place in this
region in mid—Kay. Maslowski considers the species to be reasonably
conson at Reelfoot Lake, Tennessee, in migration during the latter part
of Haw. The writer has also observed the species here in lat May.
however, it is probable that many of the birds seen on the lake are

1

resident on tne nearby Mississippi River.

Kirration of least terns does not occur rerularlt eastward free the
U u

Mississippi River, but at the only area on the Ohio River w'
are known to breed - the Bell Island ternery near Shewneetown, Illinois

I

M,

Brewer observed birds feeding on the river on may 25, 1953. Further
upstream the Species can be considered only as an occasional visitor
in spring, though Mumford observed a flock of 17 birds on June 3, 1950,

at the Hove ace Same Preserve, Posey County, Indiana (about 15 miles

as
t—Q
r1

north of the Bell Island ternery) These were either migrating birds or

a resident group from a ternery still undiscovered on the nearby Ohio

River.

From the area near the junction of the Ohio and Mississippi Rivers
northward and westward to Kebraeka and Iowa few mi ration records are
available. The birds are usually seen near St. Louis, Missouri, but
generally not until June (Comfort and Brewer). At Springfield, Illinois,
terns are occasionally seen in migration during April (Pettingill, 1951).
This early da+e is difficult to explain. Dr. T. E. Musselman at Quincy,
Illinois, on the Mississippi River has never recorded the least tern
there in over 40 years of observation (Smith and Brewer). This is in
direct correlation with river conditions above St. Louis, Missouri,
which are not favorable for nesting terns.

So far as is known, no regular migration occurs further north along
the Mississippi River than its junction with the Missouri River, though
records show that this has not always been the case (see summer dis-
tribution). The movement of the terns swings westward, following the
course of the Arkansas River into Oklahoma and Kansas and the Missouri
and Platte Rivers into southern Iowa, South Drkota, and Nebraska (to
extrene southeastern Wyoming).

In Oklahoma, terns are usually seen in miJration during the lee
week in May. Wetmore (1918) observed terns along the South Canadian
River on May 24 and 26, 1905. Baumgsrtner gives a very early April 11
(1945) record for Payne County, and May 22 (1951) for Greer County
(recorded by Brumnett). Rice (1931) provides a May 14 date fros
Cleveland County.

Hany migration records exist for nebrasha. The followin
representative dates from a 25-rear suugary of bird migration in that

state (Anonymous, 1955). The stations listed are in order Iron east to

‘u‘u" 8 3t .

Lincoln Fey b, 1926 Kay 30, 1930
Hastings M"y Q, 19L3 Hay $0, 19§O

North Platte April 13, 1947 Kay 26, 1949
Brule June 12, 191W June so, 1947
With the exception of April records at North Platte, (in line with the
April record for Oklahoma mentioned above) the general trend is from

?te. These early arrival dates could

m

early May to June across the at
be the result of a regular cross—country migration, which enables indi-
viduals to traverse the distance to the reéions in less time than those

0 oossible

(.0

birds which follow the winding course of the riverS. It is al
that vegrant birds stray ahead of the main flocks. Nhere field observa—
tions without collecting are involved, there is also the possibility of
misidentificat'on.

Nerr Omaha Nebraska on the Miss uri River least terns have been
’ , .9

observed in migration by May 14 (1941) and as late as June 9 (1923)

V

(Anonymous, 1955). In Iowa, Youngworth (I9E5) has Observed the least
tern at Sioux City as early as May 19 (1929); howeJer, on the bssis of

over 75 records he states that in most years arrival varies between May

20 and June 1.

-13-

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-15-

Occurrence in Summer

During the summer months the interior least tern is confined chiefly
to the vicinity of +he lerger rivers. Figure 4 gives the locality of the
sumner records to be mentioned. The number in parenthesis following escl
record denotes a correSponding number on thst map. The following does
not purport to present all known dress of summer occurrence or breeding,
but the records given provide a basic pattern of distribution during the

Louisiana. The interior least tern occurs in this state on the
Mississippi River from Baton Rouge northward. Beyer (1907) found terns
st Tallulah in Madison Parish (l) in July, but found no evidence of
breeding. The species is now known to breed rather comsonly all along
thet s ream. Jeter states that the birds are coemon st ShreVeport on the
Red River (2) and found them nesting in July, 1950.

iscissibni. The terns are confined to the west s1

‘3
‘ ‘ AL.

8 of the state

fl.

along the Mississippi River. Mebbett (1390) found them nesting st Rodney
in Jefferson County (5) and Vsiden states that they breed commonly st
Rosedale in Bolivar County (4).

Tennessee. The birds are restricted primarily to the Kiss'sc'ppi
River in this state. Bartsch (1922) recorded as a nesting colony what
was probably a migrating flock of adults and young on e ssndbsr in the
Tennessee River in late summer. 3snier (1930) recorded terneries on

Aiddle Bar in Cbion County (8) and in Shelby County north of fietphis (7),

in 1928 did 1929. At Menphis, Coffey strtes tnct numbers of terns varies

with the condition of the river and sendbsrs. The erds were not connon
. - l C“ 7 ‘ t - t I
In 194/ Because cf : priLCipel nestin oer being meshed out. On a flost

trip dowu the river from fienphis to New Crlenns Coffey observed terns in

only a few places, usually near towns.

Monroe considers the least tern e rare breedin'

Kentucky.
lower Ohio and Mississippi River areas. Mengel states that it is rather
common in some places and that a large colony exists now in Fultcn
County (9) on th Mississippi River. Msslowski discovered a few pairs
there in 1957 and collected two eggs. Formerly, Monroe states thct the
tern wss an uncondon breeder at Psducah in McCracken County.

Illinois. The least tern is rare and local here in svmner. Bartsch
(1922) recorded as a nesting colony what was probably a migrating flock
of adults and young on Bird Point near Cairo (Alexander County) in late
sunner. Brewer and Hardy (Nolan, 1952) discovered a colony of orns on
Bell Island north of Shawneetown in Gallatin County, Illinois, in July,
1952 (10). The group was still present in 1955. This was the first

V

definite breeding record for toe Chic River and for Illinois. Comfort

(Nolan, 1952) states that on July 12, 1952, two downy young were ob—
served on Mosenthein Island in Madison County (11) by Anderson. Anderson
observed adults feeding young at Horseshoe Lake in St. Clair County, in
1955, but since the young were able to fly this is not a definite
breeding record.

Indiana. The least tern is not hnown to breed in this st"te.
Butler's (1898) record of the species nesting at Wolf Lake in Lake
County in Northern Indiana is probably a mistake since his description

of the nest fits that of the black tern (Chlidonias niger).

 

Missouri. The species is a rare summer resident in Mi8souri.
Bennitt (1952) states that Alexander watched adult birds feeding young on
the Missouri River in Layfeyette County in 1918 (52). King (Nolan, 1955)

found terns nesting at Mud Lake in Buchanan County in 1953 (51)-

-17-

Arkansas. No publidied records exist for the species in this state.
Vaiden writes that both the Arkansas and White Rivers have colonies of
terns near their junctions with the Missouri River in Dasha County (5,6).
It may be assumed that colonies also exist on the Mississippi and Arkansas
Rivers.

klahona. The least tern is fairly common and widely distributed in
this state, with more records from the central and western portions.
Vice (1951) lists the following summer records: * Pittsburg and McIntosh
Counties (North Canadian and Canadian Rivers)--l929 (18); McCurtain
County, Red River-1925 (19); Old Greer County—~1901; Cleveland County,
Canadian River (17); Woods County, Edith Salt Plain, (Salt Fork) (22);
Harper County (Cimarron and North Canadian Rivers)--1926 (21); Harmon
County (Salt Fork and North Fork of the Red River)—-1925 a.d 1926 (15, 16);
Cherokee County (Salt Fork); Cinarron County (Ciaarron River)-—l950 (20).
Baumgartner found a small colony on the Cinarron River in Payne County
in 1946. Lewis (1950) writes that the species is a summer resident on
Horse Creek, a small tributary of the Cimarron River.

Kansas. Long (1940) states that Tiemeier found a snall colony on the
Arkansas River near Coolidge in Hamilton County (24), and this appears
to be the only published record for the state.

Nebraska. The least tern is a common and widely distributed species
in this state.. Heineman (1945) discovered two nests in July at Merritt's
Beach in Cass County (55 . Moser (194C, 1945) observed a ternary on the
Missouri River in Douglas County (54). Haeker (1957 a,b) found colonies

on the Missouri River in Thurston and Burt Counties (55, 57). Stiles

 

* Names of rivers in parenthesis were not desi natcd by Nice but are the

principle rivers of the counties given.

(1958) observed colonies on the Missouri River in Dakota County (55

The birds occur along the Platte River into Hy ming and nearly

Colorado (South Platte). Hasker anl Moser (1945 give the species as
nesting west only to York County (50), but th is is an apparent error.
Wycoff (1950) states that a ternary has been present on the Platte River
in Dawson County (29) since 194 . Tout (1947) records the species as a
common suns or resident in Lincoln County on the Platte River (28).
Benckeser (1948) observed a snall colony on the South Platte River in
Keith County (27). On the Niobrara River, Hudson (19 H5 7) observed sin gle
terns near Spencer (county?) and Meadville in Brown County in early June.
Youné .zorth has observed the species "well out on the Eiobrara River."

Wyoming. There are no breeding records for the state, but McCreary
(1954) recor ed birds ne r Torrin‘ton and Fort Lara die in Goshen County
in early June (26, 25).

Igzg. The least tern is a regu 1ar sums er resident along the Missouri
River north to Sioux City in Noodbury County. Younéworch (1950, 1951,
1952) has recorded colonies at Sioux City regularly (56). Duzont (1955
reports that it breeds in Pottawattmie County on the Missouri River
(near 56), and this is furth er subs ta ti: ted by Pet tingill (193

Early records in

i314

icate t‘ t the ran e of the least tern in Iowa was

formerly much more extensive. Dunont (19 55) tatas that it bred in

m

Cerro Gordo County (Clear Lake) (1A) and probabl Lee County on the

k;

Hississiop oi River (12). He also states that birds have been observed

in Sec, Linn, Polk, Sioux, and Jinne c‘oago Counties. Prxe er (192a)
:t’tes th “leart t Ins have been seen in summer on sandbrrs in the Des

Moines River near Des doines in Polk County (15). Johnson (1956) ob—

served the bird as 8 JL ar nt in Dubuque Com ty on the Mississippi River.

Morrissey state that in over 15 years of intensive observation he hes

L;V .12.

0)

served no terns at Davenport in Scott County, indicrting thst the

O
U‘

eastern populations are now gone.

South Decota. The least tern is rare in this state. Over (1921)
merely lists it as occurring in summer, but Visher (1915) found it
3 for ;esrs on tne Vernitfion River in Clay County (59). Agersborg
(1335) lists the species as a sumser resident in Clay, Yenkton, and

Union Counties.

Early records indicate that the least tern once sumnered in Montcnn

VLLCA

and North Dakota. Coues (1374) records the taking of soecinens by the

..

nonbers of the Usrren EXpedition on the Loup Fork and Yellowstone Rivers
in Montana. Youngwcrth believes that even todsy a cumner's search we lJ

VMJ.

reveal scattered terns

[D

11 the way to the Yellowstone River.

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huuasooa candocaa 1 opened auuooou oz» nuance ouonaaa any

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.0020hhnuoo poses. unahoh

 

     

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Post—nuptial Wandering

1

after tne breeding season, fron early Au su st until mid -st pteioer,
least terns gather in Snell flocks Cnd can be found scnttered along the

streams,a and around lakes, ponds, and mud -fle 9. These movements will

be discussed wider post—oreedin‘ activities out tleir extent deserves

13‘

mention ere. Extensive wsHId ring is, in p rticular found amend the
immature birds. Bent (1947) states that they we tier north to Minna wta,
Ontario, and Nova Scotia, although many of these records are doubtful.
At the falls of the Ohio at Louisville, Kentucky, they 're occasionally
+ed in August and September. Monroe hrs recorded their appearance
tnere fron Aug' ust 2 to Septedber 21. Mumford observed an individual
there on AuJust 14, 19% , and stetes that Brecher and Lovell saw a least
tern at the falls on August 19, 1950. According to Mumford several
sight records exist for the Indianapolis region. Butler (1398) mentions
a epecinen from Brookville, Indiana, taken on August 22,1387. Msslowski
writes tth a male and fa ale least tern were collect ed on the Ohio River
in Hanilton County, Ohio, on Septenber 8, 1373.

Rarely, the species is noted even further away from its summer range.
Jun; (1955) collected as inns ure fess 1e on the Lake Kichigan shore at
3hr Creek, Sheboygan County, Wisconsin on August 19, 1954. He also
mentions an innature female in tEie Iiilwaukee, Wisconsin Public Museum
collection, Campbell (1954) collected two immature females on Lake

Erie in Lucas County, Ohio, on September 15, 1954.

Fall Migration
In fell 215ration it see2s probable thz-t the interior le rt tern follows

much the same route: Cs in sprin5 but apparently the mi. 5rCtion is much

more cesucl and irre5ular. It is not is '1itely known whether adults
always mi5rC te J th the young birds. The writer observed mixed 5roups of
least terns, adults and youn5, which were probebly mi5rstin5 on Au5ust
7O, l95§,a Bell Island. The dates of fall movenents are often con-
flictin5. Thus, the vc5uenecs of the situccion precludes the possibility
of analyzing the migration with any accurecy.

At Sioux City, Iows, Youngworth st tes tint departure is usually
before Septenber l, with only two later d tes, viz., September 3 and 8,
1929. Me (1931) 03: erved e flock of about 153 birds on a like near the
Missouri River on August fi, l9il, and ststes that the 53therinr was in
prepsretion for mi5retion. However, Stiles (1939) workin5 in the same
region st: tes that river con1ticns often do not allow nestin5 until
August, resulting in young still not Cble to fly by the letter pCrt of
thct nonth. Thus, the be5innin5 of fell ni gration v: ries with the

time of’nesting. Perhe the latest fell record for Iowa was of a bird

’0
m

found dead at Wall Lake in Sec Cetnty on Septeqber 29, 1912 ,(Dumont,

19i3).

’2?)

In Nebraska, Tout (1947) states that in Lincoln County his 18
record of departure wss September 21 (1935). Other records from the
state agree in 5eneral with this dCce.

In Illinois probable mi5ratin5 terns were observed at Bell Island on
August 29, 1955, and also at the Cerbondcle Reservoir in Jackson County
on Au5ust 5 ,19A9.

In klahoma, Bsum5srtner noted terns in Payne County on th eCinarron

River until October 7 (1946). Nice (1931) gives an October 21, 1377
date recorded by Coues at Camp Supply.

At Aemphis, Coffey has kept migration records of the birds since 1928,
and finds that the terns are very irregular in their departure drtes in
fall. In 1955 one individual was seen on September 24, but from 1928 to
1935 tne terns have been observed in only nine years after September 1.
In 1955, when the Species Wes rather near Memphis, no birds were seen
after August 2.

In Mississippi, Vaiden has observed the least tern as late as October
5 (1921) and October 14 (1933) at Rosedale in Bolivcr County.

Beyer (1907) noted flocks of eight or ten birds in Louisiana in fall,
but gave no dates.

Winter Occurrence

Not much is known of the distribution of the race athalsssos in

 

winter. Bent (1947) gives the winter range of the North American races
as follows:
"From the Gulf of Mexico (Louisiana coast)
south along the east coasts of Central and South
America, to Aryentina (Corrientes); and fron the
Gulf of California, south, along the west coast
to Peru (Sarayacu)."
Beyer (1907) observed least terns in suall flodcs far inland in

Louisiana in winter but it cannot be certain that these were interior

birds, since no separation of the race was made at that time.

U
01
,JJ
{11
F!
L“:

FACTOR? GCViKnlNG OCCURRENCE H“

The interior least tern does not occur eVerywhere along the streams
previously mentioned. Its localized pattern of distribution is the
result of an interplay of several related ecological factors. Basically,
these a e: (1) the presence of sandbers, (2) the existence of favorable
water level conditions during the nesting season, and (5) the availa-
bility of food.

Sandbars

2133 L. The formation of sandbars in rivers is the result of erosion
and deposition by the current. These sand and gravel accumulations are
characteristic of two geological strea. thes. The first type is found
in the eastern portions of the terns' range, where sand deposition is
caused by rivers reaching grade level. To illustrate, the Mississippi

‘iver in its course from the northern United Strtes to the Gulf of Mexico

' C

reaches grade (becomes "mature") near the southern tip of Illinois.
Fron this point on it is nearly leve with the Gulf. This results in
a retardation in the rate of flow, the velocity being supplied princi-
pally by the force of the head waters. It can theoretically dig no

"taster," the Gulf of

deeper, being inhibited by the water level of its
Mexico. It assumes certain characteristics which are favorable for
least tern nesting. Its course becomes neandering over a brord flood
plain, and the slowing of the current causes the deposition of suspended
sediments and the resultant fornati:n of ssndbars and shallow water
areas. The Clio and Missouri Rivers' master is the Mississippi River.

In their headwaters these two streams are relatively SLFCIJGL, with

narrow valleys, strong currents, and fewer sandbors. As they approach

(0
E?
p.)
Cu
(7‘
O
H
:3
("F

he Mississippi River they natur o drop sediments which form

bars. Sandbars also occur on immature stredns where a temporary grade

is reached or a tributary stream causes slowing of the current. The

Missouri River exhibits these last characteristics on its upper wrters.
The least tern in not known as a breeding species on most parts of

L

the Ohio River. Above Owensboro in Daviess County, Kentucky, the screen
is relatively immature. Below this, sendbcrs are common. (“as Fiyure 5
for illustration of the imuature stream conditions.)

The Mississippi River north of its junction with the Missouri River
is an imncture stream. Foraerly he many tributaries on its upper
water: provided enough sandbars, at least in the eastern Iowa region so
that least terns occurred sparingly in sunner. Horriseey sentes that in
recent years the maintenance by river authorities of a nine-foot channel
by dams along the river has prevented the fornation of sandbsrs. On a
flight fron Divonport, lows, to St. Louis, Miss uri, he saw no bars
above Keokuk, Iowa, where they were once prevalent from June to fiepteiber.
f done on other portions of the Mississippi and Xissouri
River system, if continued, may in time further reduce good lezst tern

l
nettin? sites. At Sioux City, Iowa, Youngworth (1952) writes that

’3

‘ “oo o v‘o

*overnment work on the cnanncl of the .iesouri niver, such as revetments,

._ i '1 - .,- A a i . , , L‘. - , as -
dihes, and pllluoe, dcy cau e the orns to move furcnsr upstre n :n-ro
. I . " ‘ .r‘ I: Q 1 ‘- F-L o L‘“ L r ,- Q—u
orrs still SXIGL. FEfiJRfCa o — 3 il-usor .e so.&3cm. one ooze i chairct51o
4 C [Vane-1
~l. Cb4-_U J.
m. T'- L“ o 4- 4- ‘ ‘F‘ ‘0 J',‘ ‘ f ' ‘ "'3
pre 11. 11 0 western stroicne o- die 1; at t~rne r31“: J-:ie

1 . n * r‘ .< s - ‘L r- ‘ ‘ r- L ‘A ‘x ‘ ‘ ‘-“ ’ T. A " .
level is a less idiorcane foCtOF. On such screams [s on; upper mlScOcrl,

Platte, and Cincrron Rivers the controllin; factor in the formation of

.J o
{—14

sendb rs is an ar sunier condition. In the plains arcs heavy rainfall

\ .' 0 .' -' V‘- ‘ . " .J' L‘ \~ I‘ ' w + “.‘1
comes in wiitor and sprinb. nu UQGLG seasons tne cor—s:

, ,
.J.‘

O

I- r ~ ‘0 . f3
:4“). t flood

I!

3 ' srry large amounts 0» sediment. In sumner very little rain

U)
(f‘
(‘3
(D
9)
:5
f!
0

falls. Th result is an abrupt lowering of the water level (or couplets

(D

tnruiustion of flow) and consequent deposition of the large quantities
of sediments. Figure 7 illustrates these summer conditions. At this
time there is often more sand than water.

Duration. The mere presence of sandbars is not the only limiting

factor. The life of most bars is short, lescin often only from one

i.
D
D
0
ci-
0
C:

flood to the sually, a new bar will be formed nearby so that

terns are not eliminated entirely. As nentioned previously, Coffey
found the terns rathe' uncommoz at Memphis during 1955, probably because
13 main n sting bars was washed out.

The Bell Island Sandbar has existed with frequent chsnées in fora

natives of the area recall its formation at least

H)
(J
*1
O
<
(‘J
' ‘5
(+-
(I)
L)

!<
(T)
"D
*1
(.0
o

graphical map of that locality printed in 1958
shows that it was present in reduced size at that time. Probably the

*‘n
0‘.

larser and older bars craduall accuire the larger terneries althou
D O .L .3 ’
'ata are not st hand to prove this.

Heirht above wfter. A bar which is im;ersed b' edall rises in Water

1

level is not suitable for a ternary. The Bell Island bar at its carter
is about ten feet above the water, and the ternary is situated from
about five to ten feet above water. In the plains area where little

or no water is in the stream bed during the summer this elevation is

less important.

't

Isolation. Isolation plays an uncertain role in the success 0 a
ternary. A bar which is readily available to land predators and humans

is less suitable than a ar completely surrounded by water. Youngworth

states that at Sioux City, Iowa, terneries are always located on bars

-97-

surrounded by water. Published literrture and personal connunication
indicate thst the situation is rather variable.

Bell Island is connected to the mainland, but its large size, a
heavily wooded area near tnis connection, and locativn of the ternery
over one-half mile out on the bar, provide good protection from humans
and most animals except other birds.

Water Level Fluctuations
Tern colonies are in constant danger of being inundrted by flood

aters. Marine lesst terns occasionally suffer from tides. Hagar (1957)
in Massachusetts fonnd leest terns nesting so nerr the ordinary high
wster mark that any unusual storm or tide washed away the eggs and young.
However, the phenomenon of h 5h—water conditions on rivers is far more
regular, occurring in spring from March to nidaJune.
larier (1950) presents data which indicate that the initiation of the

breeding cycle 0? the terns nesting on bars at Henphis, Tennessee, wn

(0

closely correlated with the fall of the river to normal water level

after the "June rise." In even an average spring rainfall the Mississippi
River system drains so vast an area that enough high wcter occurs so that

he sandb rs are immersed. When the river has reached low water again
(by late May or early June) a final rise usually occurs. Ganier (1933)
noted that in a period of ten years at Menphis the wcter drOpped lower
‘than bar level about June 18 on the average. Figure 9 shows Ganier's
czorrelations of water levels with beginning of nesting. In 1928, with
Ediéh water occurring until mid-July, terns nested later. In 1921, with
r10 high water after May, terns began nesting early in June.

Vaiden believes that the beginning of nesting is governed by water

‘

lesvels. He usually observes birds ceginning to meet at Rosedale,

1".)
m

Mississippi, between June 10 and 15, since bars generally become exposed
during the first two weeks in that month. In sons years nesting there
has been delayed to as late as July when rains on the upper waters kept
river levels hiéh.

tates that in 1928 sandbars on the Platte River in Lex-

Tout (1947)

(D

-4

ebrr ks, did not appear until July. A visit to

L0
( D

ington County, 1
terneries on July 23 showed that most of the 18 nests found contained
eggs and a few young. Thus, nesting probably began immediately after
the appearence of the bars.

In Iowa, Stiles (1959) observed that the Missouri River at Sioux
City is usually not low enough for bars to be exposed until the first
week of August. This condition in 1957 esulted, as already mentioned,
in young still not able to fly in late August. According to Stiles,
flood stage at Sioux City is 19 feet. Sandbars start to appear at eight
feet. The maximum level for 1957 occurred on June 21 when the water
stood at 11.8 feet. The minimum was on Septenber 25 at 1.6 feet. The
maximum for 1958 was 15.2 feet on March 24. On June 28, 195?, the water
stood at 11.5 feet, but the maximum sumner rise was not until July 8
when the level rose to 12.7 feet. Bars became exposed on July 25, 1957,
when the river levels drOpped to 8.4 feet, and on August 7, 1958, when
the gaLge showed 7.2 feet.

Apparently the conditions found by Stiles were not typical. Young-
worth (1950) has observed young able to fly and being fed by adults at
a nearby lake in the Sioux City region on August 7. He also saw a large
flock of perhaps 150 birds, including young and old, on a Missouri River
sandbar on August 5, 1951 (1951).

At Bell Island in 1955 water levels were such that the her did not

appear until the second week in June. Figure 10 shows that the June
rise began about May 21 or slightly before. The gauge at Shawneetown

is out of the water below 20 feet. Pool stage (which may be considered

 

the normal summer condition) is 10.9 feet. Since the bar is approxi-
mately ten feet, at its highest point, above pool stage, a river stage
of 20 feet would place the water about even with the top of the bar.
Thus, before May 15, 1955, the sand was at least partly exposed. It was
immersed from May 15 until June 4, at which time it again became exposed.
Water levels dropped steadily, according to the official river observer,
at Shawneetown, Illinois, until pool stage was reached in mid-June.
Nesting probably was initiated econ after the bar appeared, since
several nests with eggs were present on June 20. Because of severe
drought conditions, water levels remained nezr pool stage during the
remainder of the nesting season and through the autumn. Minor fluctua—
tions of one to two feet occurred periodically as a result of dam
operations on the upper Ohio River.

Once low water stages have been reached, large floods are rare in the

arert hazard is not

eastern part of the terns' range. Thus, the g
destruction of the terneries, but delay in the breeding so t
is either exceedingly late or not attempted at all. Vaiden observes.
that on the lower Mississippi River fluctuations of any great magnitude
free rain on the upper waters tor the spring floods are rare, since a
considerable ancunt of rain must fall to cause a rise of more t*an a
few inches on the lower river.

The possibility of a sudden rise of water sufficient to inundste the

terneries is much more real on the arid plain's streads. Baumgertner

st tes that in Oklahoma nesting sites in the river bottoms and on the

-7Cl-
/

salt flats are at times destroyed by water. The small colony on the
Cinarron River in Payne Count\, according to that writer, must be
covered by flesh floods several times during sous seasons. These

1

streams are nearly dry most of the sunser, but their proximity to

.‘

western uplands subjects tnem to these flash floods from rainfall in the
znountains.

The preceding date would seen to indicate that be;inniné of nesting
is directly correlated with cessation of spring floods. From this it
might be assured that in those exceedingly rare years when alnost no
rises in water level occur, terns might begin nesting earlier. Gsnier':
(l9i0) 1921 correlations (see Figure 9) indicate such a supposition is

slid. However, on July 2§, 1952, King (1,33) found an estimated 15 to
20 pairs of least terns nesting st Mud Lake in Buchanan County, hissouri.
Four nests still contained eggs. Mud Lake is an ox-bow lake in the
Missouri River bottomlands not far from the river. Thus, it is possible
that flood waters did cover the lake in spring. If not this record
*might be good evidence against the correlation theory.

Further investigation is needed on the problem just discussed.
Greater knowledge of beginning of nesting and flood stages might reveal
that a physiological adaption hes evolved in response to the flood
conditions which exist so regularly each year, and that the birds could
not nest earlier if conditions were favorable. Youngworth agrees with

this theory.

   

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River can“ sandbar forntion.

-32-

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Weather Conditions
Casual weather observations made by the author in the Bell Island
ternary and data provided by the ‘eather Bureau at Evansville, Indians,
were quite comparable. Rainfall at the two localities differed sons-
what; consequently, these measurements were obtained from the official
rainfall and river observer at Shawneetown, Illinois, one mile from
the ternary. Figures ll and 12 illustrate these weather conditions.

Tenperature. The weather factor of most importance in the life of

 

the ternery is tesperature. The nesting site is always completely
exposed to the sun, which causes surface temperatures of the sand to
range from 5° to 150 higher than surrounding normal air temperatures.
Stiles (1939) found that in the terneries near Sioux City, Iowa, sand
surface temperatures frequently exceeded 100° F., and he theorized
that incubation of the eggs was partially by the sun. He examined one
egg which was nearly ready to hatch, but for which his observations
indicated little incubation by the parent birds. It is generally ac-
cepted that the Optimum temperature for successful incubation of most
birds' eggs is about 95°. At Bell Island both air and sand surface
temperature exceeded this by as much as 15° on many days during the
nesting season. Such temperatures would probably be harmful to the eggs.
Shielding the eggs from the sun was necessary here to protect them.
High temperatures can also be harmful to young terns. Since no
shelter from the sun exists, the young suffer at temperatures of 900
unless brooded by the adults. The author saw no young whose death was
attributable to the heat; however, when the chicks were being weighed

and marked they usually ran into the shadow of the worker or occasionally

inside his trouser leg.

325d. Wind serves to modify temperature and humidity, but with
increase in velocity may cause miniature sandstorms which cover the eggs
and/or young. Ganier (1930) believes that such stores may be an im-
portant mortality factor. Stiles (1959) found a single egg partially
covered with send, as already mentioned. Exanination showed that the
fetus was alive. Thus, burying of eggs may not be fatal in itself, but
becomes so with the resulting neglect by parent birds.

Tout (1947) found several dead least te ns on sandbars of the Platte
River at Lexington, Nebraska, on June 17, 195§. A small tornado and a
hail storm had crossed the river througn the ternary on Kay 22 and June
7, respectively, reducing the colony to about half its former size.

At the Bell Island ternary no sandstorms were observed that were
large enough to cause any damage to nests or eggs. Composition of the
substrate is an important factor in the effectiveness of the wind. The
Bell Island bar is largely coarse sand, but the majority of the terns'
nests were on the gravel accumulations which are not affected by ordinary
winds.

4§EEE° Summer in most of the Mississippi River drainage is a period
of low rainfall. When local rains occur they are usually thunderstorms,
bringing torrential downpours. Their effect on the terns is occasionally
disastrous. On July 8, 1950, Jeter found a ternery at Shreveport,
Louisiana, that had suffered considerable damage by rainfall. He found
a broken eggrshell, an egg in the sand which had been washed from the
nest, and nests ‘hich appeared to have been disrupted.

The year 1955 was one of severe drought in the Midwest, and conse-
quently rainfall at Bell Island was negligible with no damage inflicted.

Associated with this was the ercentage of sunlirht. Table I shows that
.3 Q

few overcast days were recorded at the ternary, and also summarizes the
other weather conditions.
Food

Composition. The food of the least tern consists alnost wholly of

 

aquatic macroorganisms. The Marples (1941) found that the principle
diet of the species in England consisted of 1.87 per cent fish, 96.88
per cent crustacaa and 1.25 per cent marine molludcs. They found no
trace of freshwater forms in the diet. Collinga (1929) states that the
least terns at Blakenay Point, Norfolk, England, fed principally on
fish, sand eels, annelids, mollusks, and crustaceans. Witherby (1941)
writes that the least tern's diet, based on analysis of six stomachs,
consisted entirely of animal matter of which 97 per cent were crustacea
(Mipidacea, etc.) and Annelida, 2 per cent were fish, and 1 per cent
were marine Mollusca. Four stomachs reported by other writers contained
small fish and one was full of sand eels (Anmodvtes).

Such a variety of food is not available to the interior least tern.
Observations indicate that its diet consists almost wholly of fish;
however at Bell Island, arawer examined the st mach of one specimen and
found that the contents were one small unidentified seed, and a fraguent
of an unidentified insect. It is probable that these were both con-
tained in the diet of a fish which the bird had eaten. At no time
during the observrtions were the terns seen to catch or carry anything
except snall miniows. These were occasionally found on the sand wnere
they had been drapped by the birds. They all appears! to be of the
same species, but were hardly iden‘ifiable is their alxays mutilated
condition.

On July 27 the author seined the shallow waters immediately sur-

rounding the island where the birds fed. Using a 20-foot seine, four
50—foot circular drags were made. The collected fishes included 297

minnows (Eotropis blennius); 57 suckers (Ictiobus 39.); l gizzerd shed

 

(Dorosoma ceoedianum); and l sunfish (Lenomis sp.). All were less than

A

two inches in length. The river shiner (Notropis biennius) proved to be

 

the same as those found discsrded by the birds, and probably was the
dominant food of the terns.

Availability, Terns are seldom seen feeding outside the shallow

 

water areas of the river. fiany writers hsve noted thct they feed on
nearby shallow lakes and beyous, where these occur near the terneries.
On these parts of fine river where sendb rs are abundant there are nearly

always many shallows. Where these do not occur the birds msy have to 50

long distances For food. In the arid plains regioLs the streazs often
go completely dry and the birds then seek water holes end congregate

in large numbers to feed. Tout (195%) found such a situation in July,
1954, when there was no water in the North Ple te or South Platte
Rivers west of the Lincoln County, Nebreska line. Water was present

V
t

in waterholes from Birdwocd Creek and drainage ditches, and Jere dozens

of least terns were

-39-

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TABLE I. S MJARY OF FRI CIRAL WEATMER VACIDRS FOB
Tit LOhfii OHLJ RIVSd TALLBI IN SJHHEB 195}.

 

 

 

 

 

 

 

 

 

 

 

 

Addi t final Rewrite .

 

 

 

 

 

10 K Tennerature PT3C1Uituti n Wind Sunsnine
r { W: . .. _ ,
J5- (De rees F.) .Incd.s) (w.?.n.) (Per Cent)
fir- -- ~+

Kent; lax. min. Ave. hater Ave. Mar.
June 1‘1 ,3 €{.d 1.33 ‘3.“ b7 90

My en LLJS-B+n_§-93._..___.._Zel J; T *1
August 100 ;3 L.77.le 1.dl 0.7 29 l 90

 

 

 

 

 

'June was tne Iourtn warmett and driest June on record with

q I
an average temdnracuze 3.0 a;nve nsrual. On 23 days Cue tennerw-
ture exceeded 900. Tue average relative numidity was 75 eer cent.

. , 0 u
July uad 80 days witn tennerattres over 93 . lne averaxe rQEL-

cive Humidity was 31 mar

cant.

I‘

A gust and 18 days witn tenneratures over 9T0. Tne averaxe

relative nnmility was 7%

ner cent.

 

All data except nrecioitation records from U.S. Denartment
of Connerce, Weatner Bureau, Local Climatological Data
Summary, Evansville, Indiana.

Precinitatinn data tron Climatological and Hydrologic Observ—

ations suooliea 0'
Illinois.

tie cifictal osserver at SJLWHGBCOW1.

LCCATIC} Edi?) DESCRIPTICL; r r113 311:2:3: senor max.

Location
Bell Island is an islsnoo only at high-water sta3c s. At normal summer
ater level it is a peninsula extendin3 downstreazn from tie Illinois

\ u o . "I’WO‘ o I
snore of the Ohio River, located at latitude be 3'; longitude 57°43'.

:4

On the United St ates Geolo aice 1 Survey topogr aphice map of the Shawnee—

town, Illinois quadran3. Is it is situated in township 9 south, range 10

1

east. Figure 15 is m1 pted from the topog aphical map and shows the
overall view of the island and river.

There is some question as to whether the sandbar is located in Zen-
tucky or Illinois. Local authorities consider it a part of Kentucky.
Accord in3 to Uni ed St tes Geological Survey Bulletin 817 (1930) the
north bank of the Ohio is the north boundary of Kentucky, the exact
line being fixed oy tie low-we car stars of the river. Since at low-water
the island and bar are broadly connected to the mainland of Illinois, it

will be considered as part of that etc te in this paper.

Description
Bell Island is one of the largest and oldest islands on the lower

:3

Ohio River. Fron its juziction with th3 . mud to the outermost tip it
mes :ures approximately 6655 yards. The hiDher, older and more stable
portions are covered witi a dense flood-plain forest similar to the t on

the adjoining river banks. The trees ran3e from about two to five inches

in diameter. The dominant spe ies are black willow (Salix n33ra

 

cottonwood (Populus delto ids s) and re d masle (Acer rubrum).

A

 

 

N

n s HL 0 ext on s 2 rds wn ea 3 re ‘ rm 8. v o ’
T‘e a ib' 'r > d 249 9/ Q0 str afro tr oute o + mo dland,
and at its widest point it is about 6?0 yards across. The total area is

Q60,805 square yards or about 120 acres. Its height above water level

way from the shore ran es from five to ten feet, and this portion of
the bar fo':s a sort of plateau slopin3 gradually to the water on the
nainstream side, dropein3 off sharply to the wcter on the la3oon side
(between the peninsula and the river bank), and failing rather abruptly
near the point to ex area of silt and sand so near the water level that
it is submer:ed with the slightest rise. Figures 15 and 14
e size of

idea of the lar the bar, and illustrate some of the points

just mentioned.

4m.

 

Iigure 13. Tue mainstream side of tne oar. Note tne gradual
alone of tne snoreline no the water.

 

 

zigure 14. Looking upstream over tne broad expanse of Bus
bar. Note tne driftwood accumulation left by receding
flooawaters.

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-233-

THE BREEDING CYCLE

At the time of the writer's arrival on June 19, e33-layin3 was well
underway and most of the courtship had been completed. In an a t apt
to piece to3ether the basic elements of the pre—parental phases of the
cycle, it was necessary to rely to a 3reat extent on the observations of
others. Richard Brewer made linited ooservations in the vicinity of the
ternery several times during April and Max, and a few observations of
courtship were recorded after the author's arrival.

Arrival in the Nesting Area

Several authors, including Palmer (1941) and the Marples (1954), have
described various methods in which common terns arrive in the general
area of a ternary. The aithor found no such classifiable arrival habits
with the interior least tern, either from the literature or from personal
observations. The birds travel in small loose flocks, and their arrival
in the region of the ternary is 3radual. Vaiden, though he emphasizes
that his observations were casual, has observed flocks of from 5 to 20
birds probably in migration and feedin3 along the river near Rosedale,
Mississippi.

It has already been shown that from mid-May until early June in the
central part of the birds' ran3e flood waters usually cover the nestin3
bars. Thus, when the terns arrive they cannot go directly to the
ternery but must wait for the water to subside. At th‘se times they
can be seen feeding alon3 the river and nearby bodies of water or
perched on drift accumulations. Courtship may begin at this time.
However, until the bars are exposed, continuation of the cycle beyond
courtship is halted.

It is this fact which sets the interior least tern apart from coastal

nesting terns, since the latter are almost never deterred in the breeding
cycle by flood waters and may begin nesting activities as soon as they
arrive. Thus, Palmer (1941) and the Harples (1954) found in their
studies of the cannon tern that in mid-nesting season nearly all phases
of the breeding cycle were being carried out concurrently by differen
pairs within the ternary. Individuals which had arrivrfi late were in
courtship, while other pairs nearby incubated eggs.

With the interior least tern the activities of almost all members of
a colony are synchronized by the high waters so that with few exceptions
all pairs are in the same phase of the cycle at the same time.

Courtship

Courtship display in terns is rather well known. The same basic
performance is found in nearly all species with variation in each
species and in individuals. In the least tern the different phases of
display in their approximate order are as follows: aerial glide,
posturing, parade, copulation, and incipient nest-building.

The author observed courtship among a group of about 10 terns at Bell
Island on June 20. These were birds which had arrived late, since
egg-laying was underway in the ternery. They were perched on the
mud-flat point of the bar or flying over it (see Figure 15). It should
be stated that designation of individuals as male or feusle in this
paper is not certain, but is based on the actions of the birds, occasion-
ally corroborated by observed copulation.

Aerial flight. On several occasions a tern carrying a small fish

 

flew and glided at a height of about 50 feet with another bird following
closely. Their positions soon reversed. In flight they maintained a

peculiar quick deep wing stroke. Palmer (1941) states that the ae-ia1

glide in common terns is a continuation of the fish flight, a social

 

activity taking place before cogrtEKip. There is :pperently no well’

defincd fish li ht in the least tern. In feet, in contrast to toe

well-defined and co plex flights of the conzon tern, the serial gliie

in the le st tern is rfire : c ec~1i“uly litignificsat.
Posturi r and parodiit. Whereas the aerial glide may at times be a

.3

is ”A integral part cf courtship. According
to Palmer (1941) the activities of courtship are not necessarilv a sort

of the mating phase, since it is extremely probable thet sctusl pairing

0 1 A 1 r ‘ V ’ a f (V o n V 10" v n f! 1" \ I ‘
CL tne erns nee elreeiy tanen place e rlier in tnc syriug, or tne sires

‘

have been meted since the previous summer. Courtship, tnus serves to

1

break the social relctionszio benevicr, inhibit male oeh vior in the

fensle, synchronize the reproiuctive stetcs of the yeir, maintain the

In the intJrior lecct tern the eeriei glide may be quickly followed

by the birds coming to earth and posturing. The following is an account

of a typical example of posturing and para-in; observed at the point on

.4

[)4

June 20.
As several bi is stood near the edge of the weter enother_tcrn,
probtbly a mels, flew over the group with a little fish. All the birds

in the group celled kueu-hueu-kueJ-kueu as the flying birfi "A" passed

 

overhead. A eli'hted besiae one iniiviiuel "3" in the

\‘|‘
C)

rushed ct "A" and sttemnted

O

1. '3' .-,.‘ ,J,’ t. '4. ""3!
as fish. InStUuQ of suing lb :

offerei t

to peek him. "A" then flew hurriedly away but soon ephroached another
tern "C", still carrying the fish, and presented it to "C." Instecd of
rushing at "A", "C" assumed an erect pose—~with he~d held high. "A"

then assumed a bent pocture——with beck hunched, head down, wings drooped,

and bill parallel wit} the ground. Rollin; the 'i3‘ nerr the caudal
fin, "A" stood still while "C" shuffled 'n a counterclockwise direction

around him. “C", after makinr

a.)

about one circle, suddenly took the fith

"A" and etc it. "A" thei postured with bill pointed upwerd st ADO

from
and wings raised but directed beckwerds. In other observations of the
ease procedure the "C" bird did not eat the fish but drooped it sfter
holding it momenterily.

In the first presentction to "B" the negative resction of thet bird
indiceted hot it was :lso a male bird. Terns epoerently cannot die—
tl““h]’n be ween sexes by plumage but rely on the described procedure.

The point ores nrobe bly was not port of the ternery, since the birds
gee reactions in

disregerded the observe er he s in contrast to their do

"3

the nest area. Thus, courtship, in contrast to that in common terns
(Palmer, 1941), did not t::e place within the ternery, at least while
the writer was present.

Ceruletion. Courtship bonevior at Bell Islnn was not observed to

 

terninete in conulccion. Stiles (1979 found thdt 168?e terns at
- \ /

‘ ' ‘ a "-A \ I‘ I 1 o “- ' ' 'F‘. r~
Sioux City, Iosl, beuzn copulstion soon e.ter arrival in may uni con-

tinued through June end July. At Bell Island coauletion wus not
observed after the third week in June. he following procedure of the
sexual act was noted at the point (where the courtship observstions we 0
made). It Wes not preceded, e.t le:: st 13 E‘diEZCly, by the ; rode.

Two birds stood side by side. One wrs in an erect gositirn, the other
stooped with heed down and wings slightly extznded at the sides. Both

birds moved their heads fron side to side. Tie ere ct bird moved close to

the crouched bird and mounted. Both birds celled ‘tuc u—muei-rutd- Leu

 

with bills closed. Copulstion lasted about three seconds during which

time the birds' bills were interlocked. subsequently the male flew away
and the female remained. She prcened peseively and gave no cell.

Stiles (1939) observed an interesting variation in the courtship
procedure. The routine which he describes seems to combine the ac ial

.'

glide and copulation and omits tne posturing and perede phases. After

\

execution of the aerial glide (es described earlier) th

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of Palmer {1941) or the vee eocr of the derples (19y4). The biros were
very close together in this dive, end as they e-i;hted on the weter the
\

female took the fisn from the male which was almost on her before they

reached the water. Cogulation took place quickly and lasted only a few

Incipient nest-buildihc. This includes scrope-muking and pebble-toss-

 

’1

1e least tern. It may occur before or alter copulation. Both

sexes participate, but according to other workers these actions by th

('0

male stitulete the feicle to perforn similarly. Terns at Bell Island

were not obse ved to make these artificial nests during courtship, but

the bar was covered with hundreds of depressions, nede by the birds,

rs. It may thus be essuncd that the act wee ter-

(JG

which contained no e

formed earlier. Pebble-tossinv replaces the twig-tossing observed by

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Palmer (1941) in season terns. Since least terns use no not riels

5

other tnsn the gravel substrate in constructing nests the reason for the

substitution is obvious. Pebble-tossin* was not noted in the courtsnunst

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Bell Island, but, elder (1941) points out, such activity may be

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carried over into other passes 01 t

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ne cycle as a substitute activity en-

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ployed in tides of anxiety. Thus, at Bell Island, t.e pebb

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As soon as the nesting bsr bec01e3 exposed it is occupied by the
erns. The send dries quickly, so thft the birds are not helpers? by

moist conditions. At Bell Islend, egg-laying probsbly beisn very
shortly after occupation, for at the tine of the writer's arrival on
June 20 the bar could not have been exposed more than ten or twelve
days; still most of the nests contained eggs.

Size of terneries. The size of interior least term colonies is
variable and is difficult to correlate with any physical chsrectcristics
of the habitat or with the area of occurrence within the range. In

general a direct relation exists between the siz- of the bar and the

(J

colon‘. The larger colonies usually occur on the larger rivers which

4.7

possess one larger bars, although there are exceptions to thi

U)

Vaiden believes thst 23 pairs is about the maximum number per colony

in tne Resedele, Mississiooi, re5ion on the Mississippi River. This is

fever thin found by other workers on the lower osrt E that river.

0

Coffey (Senior, lT50) found about 50 birds present on Middle Ber
nesr Memphis, Tennessee, on July 31, 1928, and found three nests in this

J.

colony on August 5. It is probable that this small nunber of nes

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not good evidence of the size of that ternery. Austin (1949) states

II‘

crones"

that there are few non—breeding adults or in common tern

colonies, therefore the nuxbor of birds can be used as a good indication
of the size of the nesting pepulation. This is probcbly true with least
terns also, and was definitely so in the Bell Island colony. Thus, the

50 birds observed by Coffey may indicste a colony of about 25 pairs.

On July 13, 1929, during the height of the nesting season he found 15

nests in the same area.

Mengel noted a colony of 40 or 50 birds at "Kontucfiy Bond" in Fulton
County, Kentucky, on June 15, 1937. He found no nests and it is probable
that at that early date no eggs had been laid.

On the upper Missouri RiVer in Iowa, tiles ( 959) found that terns
nested in small colonies of 10 to 12 pairs. In nearby South Dakota,
Visher (1915) states that colonies of 7 to 8 pairs are the rule on the
Vermilion River near its mouth.

In the plains region the colonies are generally smaller. Nycoff
(1950) notes that a ternary at Lexington, Nebraska, on the Platte River,
never contained more than six pairs in 12 years of observation.
Bencheser (1943) observed a colony of five pairs on the South Platte
River in Keith County. Tout (1947) in 1928 and 1929 found from 17 to 22
nests in terneries at North Platte, Nebraska, at the junction of the
North and South Platte hivers. These are un‘sually large colonies

n; from othe records from that state. Long (1940) lists a colony

’4.

juds
of five pairs at Coolidge in Hamilton County, Kansas, on the Arnansas

River.

On the nod River at Shreveport, Louisiana, Jetor discovered three

R)

nests and saw about 0 birds n July 1, 1950.

In the Bell Island ternery there were between 55 and 63 birds present

:ht of the nesting seasons of 1‘52 and 1955. On June 25, 1953,

—‘
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at the hei

in mid-afternoon, the writer was able to count 28 incubating birds fron

the blind. It is probable that some birds were not at their nests, and

L+

no all nests could be seen from the blind. Thus, it is known that

1

there were at least i0 nests nere. This coincides closely with the

‘

number of adults counted on several occasions wnen the whole group was

in the air chasing a crow or vulture which had ventured too near the

\‘ N

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terns: y (see t.e section on social activities).

\I)

()

The Bell Island ternary is one of t-e large t, if not the la 5est,
of tne interior least tern colonies in existence. In published litera-
ture or in the personal correspondence of VLIIOUS .orhers wit‘n tle
writer, no ler5er terneries nave been reported.

: L- ' .L'-... n #1....» - '. -. . ‘.~* 1.- - .. :1. '1
Discrisuciun oi U¢C 91? s in tne ternery. Le up terns, unlixe other

 

 

 

closely related scecies, cnarectcristically do not nest in ccnpact
‘rcups. Vnidsx reports an exec; tion to this in the disc.very o: 14

pairs nesting in an area of not LOTG than one-quarter acre at Rosedale,

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Lississippi. Stiles (193$) stctes that in Iowa, t”
well scattCIed--often as much as 50 yards apart. Nycoff (19 53) reported
a maximum of six nests in an area 75 by lie

The Bell I

(1)

land sand ur is approximately l23 acres in area.
could have c oxceivebly nested anywhere on this area with little dax

from flood waters. The ternery Was distributed over an area cf about
53 acres, givin5 a densitv of about .7 nests per acre. me fi 5ure

does not 5ive an accurate picture of t e distribution of nests, however,
for generally SPBCKI‘T they were located in 5roups of five to ten
so ewhat closer to 05e tth then inlicat e . During the first part 0
summer study the writer observed a se i-circle oi seven nests spaced
an avere5e of 14 feet aorrt.

Nests are usually loc: ed well be ck from the we tar. Ganier (1933)
states that a colony near Tiptonville, Tennessee, on the Mississippi
River was several hundred feet from the wcter and well out from the
xvillows. At Bell Island the ternery was in no danjer of minor water
fliictuations and was a minimum of 66 yards freq the water.

The terns probably prefer those parts of tne sandbors with a suriace

of gravel and vs y coarse sand on which to nest. There are indications
from the writings of sons observers that gravel is not required, for
they spe k of the eggs being deposited directly on the sand. chcff

at Lexington, Nebraska, that terns actually

to the gravel. He also observed terns nestin on

5
covered with seedling cottonwood: frog six inches

O

is apparently unprecedented. According to Wycol

on the bar for some years and their "dislike" for

.'

possibly overc.me by their attachment to

At Bell Island the writer found only five nests in sand.

that part

prefer the fine sand
area: thickly

to a foot high! This

the terns had nested
the vegetation was

icular bar.

Figure 16

shows the gravel areas (shaded portions of the bar) on which the terns

nested.

The gravel accumulation formed a large oblate ring (see Figure

17) which was the approximate outer boundary of the ternery and the

area of greatest concentration of nest

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Iigure 1b. Snaded areas of tne oar are graVel accumulations
on union most of the terns' nests were located.

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Territory and Defens
It has already been shown that in the interior least tern, unlike such

species as the sandwich tern (Thalass us sendvicensis) and the comnon

 

tern, individual pairs are widely spaced within the boundaries of the
ternary. Because of this, instances of territorial disputes are rare.
It is not clear just how far out from the nest the territory extends,
since it is defended less strongfly at its boundaries than at the nest.
Fron observations at Bell Island the author concluded that territories
were so larre that the word had little meaning, and disputes of bound-
aries so rare that even the birds paid little attention to each ther.
Occasionally a wandering chick and the attending parents would cone

too near a neighboring nest and would be attacked by the owner. The
latter usually walked toward the adult intruder which usually flew
quickly, or retreated a safe distance. If the intruder did not fly
immediately, the owner would dive at it until it did leave. For the
most part, though, a casual observer seeing the ternary from a distance
without causing the birds to fly would find it difficult to believe that
a colony actually existed on the sand.

The significance of the upwrrd flutter (Palmer, 1941) in relation to
territory is uncertain. In it two birds rise in the air almost vertical-
ly with tails Spread and bills open. They remain close together and
continue so, often to great heights. The Marples (1954) described it as
appearing like a quarrel over territory but having an affinity to eburt-
ship. Palmer (19h1) states that Christoleit noted the flight in
Lapwings, and thought the purpose Wes maintainence of territory.

At Bell Island the writer once observed two birds engaged in the

:flutter. They came to the ground, the male (?) carrying a little fish

which he gave to the female (?). He then assumed the bent pose with
bill and neck extended. Then both took off and begs. the flutter,
rising to 63 or 70 feet, after which they sailed away from each other.
All the while they called kibik, kibik, kibik. The fish presentation
indicated that these birds were in courtship, and if so then perhaps
the flutter is connected with courtship or maintaining the sexual bond.
Its discussion is included here since it is referred to by some authors
as a part of territorial defense. Observations of the act at Bell
Island were certainly not frequent enough to warrant definite conclu-
sions to the contrary.

The Nest

Comparison with other tern nests. The distribution of nests in the

 

ternery has been discussed. As already stated they are more often on
gravel or coarse sand, less often CL fine sand. Of all terns, the

least tern constructs the simplest nest, which is merely a shallow
depression in the sand or gravel with no twigs or other materials.

Bent (1947), however, states that on beaches where shells are present
least terns may use them to encircle their scrapes. This is in contrast
to the more elaborate nests of the connon and roseate terns which often
build platforms of grass and sticks when these are available near the
nest.

Initiation of nest-buildinr. Incipient nest or scrape-naking begins

 

 

as a phase of courtship. At this time both adults engage in nest-
rnaking to such an extent that the depressions fairly cover the ternery

grounds. Males usually make the first scrapes and are then followed by

V

1 1

the fenales which are stimulated by the Siéflt of the hollows made by the

inales. The Msrples (19§4) found that shoe prints stimulated terns to

make scrspes 0' then. At Bell Island terns occasionally transformed the
writer's boot prints into temporary nests when the young birds wandered

fron the original scrape.

Method of scrape-making. It shes a very short tine for a least tern

 

to 3000p out a nest hollow. The bird leans fOFWurd, nearly touching its
breast to the ground, and bracing with one foot, kicks the send beckwerd
with the other until a depression is made. To sold it to the body form
it nestles in the depression and wallows from side to side until satis—

fied that the scrape is suiteble.

Descriotion »f the nest hollow. At Bell Island the writer took

F ——-

 

)

meesuresents of six nests l-cstod near the blind. Their avers 0 dia-

metarg were as follows:

Nest A 130 mm.
liest B 140 mm.
Nest C 32 me.

test D 140 mm.

Nest F 12 mm.

Nest C came nearest to being no scrape at all. The othe‘s were all
well defined with a depth of about 1 to 2 cm. and were nearly circular
in outline. Figures 18 and 19 illustrate two nest hollows, one in send,
the other in gravel.

Ur‘.

1D

of the ne:+ hollows. Screpes were not only used to hold e549 and

 

ymning, but as soon as the young were rble to walk and beisn to wander

tacross the send, the parents followed them, hurriedly constructing

-tpnporary hollows in which to broad the chicks until they moved again.

a

Ufi‘rm ’CXE~-"3-.: - ‘

- Ml' ... -

 

Eigure 18. A.typical interior least tern nest at Bell
Island. None that tne scrape is on a gravel area.

3%.~’ ,.- 1:.
.6 b .I’I'?‘
o 0" '

 

Figure 19. A nest of the interior least tern at Bell
Island. This scrape is in tne finer sand used only
rarely by the birds in nesting.

-51-

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e: s. heaauremeuc: Jere rhesus 01 11 e-_c from tne

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clutches in the six 11:sts near the blind. They averu5ed 51.2 I 25.8
mm. This a5rees closely with the avera5e 5iven by Bent (19%?) and the
Marples (1934). The nee urements of the 17 e5 3 are 5iven in table III.
No differences in size which could be correlated with variable factors
in the enviror"ent ere noted.

Color o:_t:e e; s. The 5round color varied from pale buff to olive
bu t specnod and stre cited with dark 3 rple~orovn to chocolate and
blue—gray. Fi5ure218 and 19 show two typice l clutches of the interior

1e 8 :t tern at Bell Island.

o the clutch. The size of the clutch of the interior least

U)
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(I)

 

 

t;rn varies free one to four, but is usually two or th so. There is
apprrently a tendency tow rd 3-355 Clutches in the north to 2—855
clutches in the south. In the plains area two and three e55 clutches
are about equal in occurrence.
Vaiden states that at Rosedale, Aississippi, two 655s is the probable
clutch in over 95 per cent of 'he nests. he further states that while

O

three e553 in a clutch is rare, onsoccasionally foris t}1e full co Jpl -
2nent. In the central part of the terns‘ range there is much variation
in clutch size. Coffey (Ganier, 1930) noted one group of 15 nests on

Middle Bar at Menohis Tennessee in which one contained three axis
1 , ’ QJ,

seven held two, and fi ve held one. At Bell Island the writer estinated

()

that about 83 per cent of‘ the ne3ts contain ed three e55s, ab
cent two. In Iowa, Stiles (1959) states that the normal clutch is three
e55s, although one and two occasi wally io1m th ofull coeple sent. At

(Inaha, Nebraska, Hesor (1940) found two and three e55 clutches scout

equal in occurrence. Tout (19%7) recorded differences in avera5e clutch
size in different years at Forth Platte, Xebraska. In 1326 he noted 13
nests of which three held one e55, six held three, and one held four.

In 1923 he found 13 nests, of which one held four e55s, ne a chick and
an egg, three held three, eleven held two, and the rest held one. Table
II summarizes clutch sizes from selected stations throu5hout the interior
least terns' ranQe.

Table II CLUTCTZ 3121-43 or T333 ILITLRICR 113.11‘ 1‘ 3:11"

Rosedele Memphis Bell Island oicux City Onaha North Platte

Size number of Nests containin; a 5iven clutch
4 none none none none none 2

very rare 1 9 (24)** very common 12

\N

5
2 5% 14 l (6 ** uncomnon 5 9
O

[O

1 hf (est.) 7* O unconnon
*gome of these were probably inconplete clutches.
**number in parenthesis indicates approximate figure for entire tern-
ery.

Infertility of es s. Palmer (1941), workin5 on conion terns, and

 

Pettin5ill (1939), working on arctic terns (Sterne paraiiset), lound

 

thrt infertility of €558 ran between five and six per cent. In contrast,
Austin (1929) found that in a total of 17,500 8778 laid in the common
tern colonies at Cape God only one in 500 wcs infertile.

At Bell Island all e558 which did not hatch, such as those known to
iieve been deserted and those in nests where o‘her chicks had hatched at
least three or four days before, were ogened. Only three of these were
;found to be infertile. Two of the e55s were in the same nest. All

otflters which were Ofenei had chick embryos in various st 53s of develop-

ment. The apparent infertility was about 5.6 per cent (assuming that
there was a total of 84 eggs in the colony). These percentages will be
discussed further under the section on mortality.

Table III EGG DATA FCR.SIA Nears AI DJLL ISLAND

Nest Clutch Size 353 Measurements in Millimeters
A 2 55x24; 51x24
B 5 50 x 25; 51 x 25; 52 x 25
C 5 29 x 24; 29 x 25; 50 x 24
D 5 51 x 25; 29 x 25; 7” x 25
E 5 54 x 26- 51 x 24; 51 x 24
F 5 . 55 x 25; 55 x 24; 52 x 25

Egg-laying. Hagar (1957) found in a study of the least tern on the
Massachusetts coast that eggs were laid at intervals of two days.
Witherby (1941) states that with the least tern in England, eggs are
laid on consecutive days. Coffey noted in a colony at Memphis, Tennessee,
that eggs were usually laid every other da‘. Moser's (1940) observations
from Omaha, Nebraska, would indicate the the eggs are laid every other
day. The writer did not arrive in the Bell Island ternery in time to
gather any data on egg-laying. However, it seems probable that eggs were
laid on consecutive days, since in all cases observed the 3;;E_hatche

0. consecutive days.

 

Incubation

Initiation g£_incubstion. fiitherby (19Q1) states that in England

 

 

incubation begins when the second egg is laid or earlier. at Bell
Island incubation probably began soon after tie first egg was laid,

since, as already noted, eggs hatched on consecutive says.

Hagar (1957) writes that in Massachusetts adults losing their nests

and e332 during the incubation period usually renest in about three
weeks. At Bell Island this was not the case. Fron the hei3ht of the
incubation season on there was a gradual reduction in the size of the
population and number of nests. This probably resulted from e333 being
lost from predation, or other unknown causes. From daily checks on the
number of birds remaining in the ternery, it was fairly certain that
none of these birds renested, at least at Bell Island.

Lenrth of the incubation period. At Bell Island, tie writer arrived

 

so late thnt most of the e33—layin3 had been coupleted so that no
accurate data on length of incubation are available from there. The
length of the period in least terns has been much disputed. Vaiden
believes it to be from 13 to 22 days at Rosedale, Mississippi, and

co onpute s this from the date of the first e3 3 laid to the d te of the
first e33 hatched (see florth, 1940). Maser (1940) found that the period
was 18 days at Cnaha.11a"ar (1957 ) 3ives 19 to 24 days for ‘dasseC1usetts.
The Marples (1954) st ate the .u it is 20 days in 3n3land.

At Bell Island the first e33 hatched on June 50. fiith an incubation
period of about 23 days, this would indicate that the first 833 was laid
on about June 10. Since it has been shown that the bar firs. Lecaie
exposed about June 4, t1£ 'June lOd mt is at least near the be3innin3 of
err-l"Vi.Q. Since the greater part of hatching occu rrc d durin3‘ the
week following June 50, then the principal period of egg-laying was
probably from June 10 to June 17. Very little layin3 occurred after
.Iune 17, since the last chick, so far as known, hatched on July 10.

.Activities during incubation. Witherby (1941) states that with the
lea t tern in Er 3land incubation duri13 the first few days is performed

holly by the female. Later on the male rradurlly assumes a snare o

Ir; tile Beill Island ternery there was much variation in the relative

Ever"ti<:irseisicni of the parent birds in incubation. Different pairs em—

plmoywed. digffkerent methods. Basically, ther.e routines were separable into

true t.Lorewe {RDllowing types: (I) nearly equal division of incubation

dirtisas vritki the male seldom feeding the female on the nes st, and alter-

rusticni of' infinfiaatan3; and feedin3 for each adult, varying from a few

nirnxtee tn) an hour or more bet Jeen ch n e overs, (2) female performin
nu>st of time incubation with the male usually not feedin3 her on the

Inset but.‘ nuardin3" the nest or inc‘wo tin3r for a s; ort tine while sne is

n
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eeding; (5 ) fess 1e pt erfornin3 most of the incubation wit- thezwe e

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feedin? her re 3ul arl on tle nest. Fran asual obse rvat'on the first
.3 !

method seened to be the nest prevalent, the last was next150st com non,

and the second the least enployed among all terns in he colony.

H
i‘

i3ure 20, part a, shows the de3ree of atte ntiv venes s of pair D durin3

incubation. The followin3 observations are from the auti

b
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tkm't period and describe the activities takin3 place at nest D.
I a
June 24. A032.

Ban Aiult (prob: bly female) incu 0 tea.
8:32 She flies from the nest cryin3 Ree-din, kee-dio

————-—-—:—.—-————.————-I—
inzmswor to em st} or bird flyin3 over. Twice I have
noun birds flyin 3 pas t Jith fish. As the bird does
soedl terns in vicinity 3ive th's hes—dip cs 11 wit‘
mudiother chatter.

,-
.J

05 Female returns to the nest, probably fro: pursuit
avulture.

~411 in adult, probably the sane one, returns to nest

8A2 3:1 aiL It probably the mole, cos Jr to the nest
an mands nearby while fe;ale continues to incub£+°

On
I

'3 :2 "l. r _ n _ 1 ._:.°.- - h). . 3

cazluu resale :lies Cu A l~ ccuuinuu~ to teen: cv.

'1 3.x 1: 1,. -1 1, p; -3 ~

x): “J ”Cid f-n-l y inch Yes ".:r st xiiio “c : as t
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fRJr

7—? “If‘b " » -~ , J- ". _ ‘ A ‘-'.. R'r
:J : ..-- Le 153V, 8 116 («U Grills] l::::-:‘.L, , Xh'le-kl”.
-——- —* -—+

He circles once cal returns to incubate

 

3 minutes cf incubation mule leaves to
£3“ urui c: 1 of flying bird which saon hovers et ebout
ILD eet over the ne~t and finally lands about five feet
frcxn it, ' l: the nest 533 incubgtes.
prob ‘1

This is

F male still incubztes.

59:30 All biris in the aroup fly "”‘n—difi“'
crow cr vulture is

u c 4in; away. A
the FGLSOH.

to incubste at D.

Probably the

to

9:09 A gencrfl ufflight occurs as a human cpfircuchn

9 12 Birds a 1 return to nests. Probably still f
W

o . \‘ ~ " J" " 1" ‘7‘
still incuacues unless cicle

l . was a change
a. the last upflight.

9:51 Upflight as birds all pu sue a crew across ternery.

QfIZ They return to their nests.

Durtnstne 120 minutes of observation the e35: were incubfitei

approxtmflely 100 minutes or 85 per cent of the tiM'

u is. The male incu-

bstmionlylfl minutes or 12 per cent of the totel tine of incubation,

‘ n ' 1 ‘ ‘ .- ‘L ‘ f.‘ V“ '. " ‘ “ 2‘ Q ' \fi ‘\ 4" ‘,‘ »' J“ . . .-» I, I -. \ \‘u \
tnelenahaincuo ted yO ninutes or Qu per cent cf LAG ulmg oi lquJh-

‘ -\ I“: L." 1 ‘ q. ‘7‘ :1 ‘1. I‘. Q q. a, -v 0“ '1‘ . ‘lfl y~ - I n "" 3 fi ’1 '.
Armtufle fctture c: the j.cceuin uCCOuflt is tue uuiucl 0: Ug-

' a“- ‘A - - « r: . u - ‘- s ' 63‘ 1" 'V “ I ~ ‘ I ‘
lllgfifl‘mfit occurred. The terns s-luom incuastcd dlcn 0%-; use were

put toffli; t et ‘Eua

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b

"ominent cause

* ‘4.’:‘ Q 9 ‘~ ‘r‘ {"rj+‘-- 4- .
0 cu: Afi’ mi .J.e \bu;nf1‘w38 FJFE)

(or crust: (CECI'vus brecrrrhvrchcs) too nezr the ternery. rli5hts were also

(saizswsd byr laozsts on th= river. For some roE son the oi5 stop :ers seemed

to attract thetams

, eni ey often flew to the vessels and “accor-

‘9

-- a “ .1 m 0 . . AM a :J' _~\~‘ -'~ 's . u.
1J1 taruotJ.cz‘ oasczvsticn o- ctcutlveress 3*

"‘ '\
C".; .10.”:

I]. . . u . 1
:e) Until 11: 'l: {/9 $11L123?) with nly two fli“hts to tne

1.1;ocxi ti) "dififi in the water. The male was not sresent d rinr this

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entire period. At 11:15:16: assume “'0 incqufio

a .
U418 L

or nine
*nirnxtes Lnrtil 11:27 while the fesele fed and "dipdev" in +*~ la ocn.

Figgure EH. shows the feuEle of 3 incubatin5 durin5 one op he r lon5

periods of duty.

At Best I the female, as alrerdy state

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of incubst'on with the male feedin5 “

LET frequently on the nest. Fi5ure
20, part b, illustr tes the degree of attent;veness of each bird and

denotes the feeiinis. The followin5 account is taken D A +5

field notes and descrioes the set

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shown by the fi5ure.
1' / - .
June 20. A.u.

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’ A- ’d‘ 4- ‘ . wfi—r . 4.. . ’1- " "\ - .r-N : ‘ . I.
10:0j lne male co es to tne incuostinu biru c 11135 its ee-c l,
53'0Ui very rapidly. The fe isle answers witn a "yellow—le5s
_\ u, ~ ‘1 q 5“ ' t‘ n J i‘ - “1 ‘\ .
:1 " tNO-Sylladlei note. Tr e mole c rries a lian Wu;Ch .e
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t and quickly eats i'. As she
TO the nEle postures w'th need erect, bill jointed up at a
450 eagle, me E stretched outAE , and win5s hElfz J ole vste d
amiopen. ( i5ure 22 illustrst s the oe5innin5 of‘ this pos-
turin5 display.) The m:-.- e t'..en flie

call.

LAC,

n ‘R y-u r‘ 1," 1 ‘vz‘vw .
lCrS to tnc fenele which tunes 1
cs

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, (511(11):) 1.3 it'Je'uekt"Cul

 

:- m. n 11- , ' , J . ~l~ J. ,,+' -.. ' v. :l... L: ..
Mk0: the leesinQ is repeated dlofl one rOuolIo oein5 -ucncicsl
1' ‘ + -« r", a
to we fires feeuia5.

L307 Female leaves the ne t cellin5 kibick.
10:08 Returns.

10$ Another feedi35 after lo minutes.

-55-

1C) :25 Again the male feeds female.
10 : 53 Gene.

10 : 1+5 Sane.

10:50 :‘fter another feeding at 13 both adults fly, but
the female returns to incubate at 10:5 .

10:57 Z-‘Isle feeds female who leaves nest and walks to
me et him about a yard from it.

11:0’4 Again she leaves nest to get the fish.

11. :12 Feeding, usin5 the ori5inal routine.

11:2 Female leaves nest to chase a Kin5bird which
pe ches on a 105 nearby.

11:26 Male feeds female on nest.

11:50 An upfli5ht occurs in the ternery after a crow.
ll:j1 Female returns to nest.

11:55 Msle feeds female on nest.
12:00 Female incubz-‘ztes.

During the 155 minutes of observation of nest _I_3_ the fernsle left the
nest six times for a total of six minutes. She thus incubated for
95.5 per cent of the totel time. The male fed the female 12 times at
the nest, an average of one feeding; every 11.2 minutes.

The posturing display noted at nest :1 when the male fed the female
was commonly observed at feedings and in chan5e—OVers at other nests.

The male of 1_:‘_ was observed to posture even thou5h he had cone to the
nest without a fish. The posturing which occurs in fish presentation
in courtship is identical to this so fer as the writer was able to
observe.
Terns which remain on the nest for long3 ’periods of tine often sake

brief excursions to the river to “dip." This no doubt is bees-Hoe of

KM»:

the high temperature of the sand which causes the bird discomfort.
Mabbett (1890) observed that least tern eg;s on the lower Mississippi
River bars oftsr had small drops of water on the shells. The answer
to this seems to be that the adult tern sprinkles water on the ogqs
when returning from the river. The birds often hover a few feet

over the nest before elighting, and doubtless droplets are shed from
the wings and body onto the eggs.

At Bell Island a tern coming to the nest cane directly to it if
the other bird were at the nest. Occasionally the incubating bird
flew before the arriving bird was near so that the letter was
temporarily thwarted and hovered uncertainly for a few seconds,
obviously sezrchin; for the eggs. This would indicate that the bird
recognized the nest area but had no idea where the actual nest site

was located until it saw the eggs.

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Figure 21. Tne female OI nest 2_during incubation.

b

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Figure 22. Tne male of nest §_immediately after giving tne
female a fish. Tne wines are upraised in the beginning
of tne posturing display.

Hatching

At Bell Island the first egg hatched in mid—afternoon on June 50. It
was not noticably pipped during the morning check of the nests. A close
inspection of another egg in the see nest at the time the hatching was
noted showed that it was pipped. It hatched in late afternoon of July 1,
nearly 24 hours later. Palmer (1941) states that common tern e549 may be
pipped as much as 36 hours previous to hatching. Hatching did not occur
in the Bell Island ternery at any particular time of day. Several e553
were ”novn to have hatched either at night or very early in the norning.

On euergence the young tern is still wet and weak, but is able to
utter a faint reaping, peeping note audible only a few feet away. It is
unable to stand and lies resting on its tarsi (see Figure 23). The
intense heat dries out the natal down in a few h urs and there is an
accompanying increase in activit;. The chick is still not able to
stand fully upright but seek0 shelter from the sun within the scrape
by crawling slowly about.

Growth and Development
Firure 27 ilius rates the growth of the young least tern and repre-

sents a "typiC"l" dev:

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lopsent fron data on 20 chicks. fie chick was
observed throughout its QFOWth to flight stage; indeed, verv few wer"
watched for over four or five days of this eeriod, since they wandered
freely over the s ndb r by the second day after hate in and were very

(difficult to locste. Thus, there are lcr e gaps in Walékt and plumese

a. < ‘ , ' L ..-
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1. .— ‘,. - r - ' . A A .1‘. ' ., . a. ,- ‘ ' 1- L .. . .: 4“ . m“ ,.
(tarsus aoout 1.4 centimeters), enroliné bJe CxlCu to run swiitly. in:

w a j a _ ‘ . _\' "w u _ . _ . h __ ‘ y . ‘ 1’ a.“ '
sire is extra sly w-ry and diffiCult to find or catd;. Figure 2e shows
a tern about two weeks old.

'lyin$rjuvenal stare. The chick flies at about 23 days of age. The

 

..

plumage is much like thzt of the wo—week—old bird, except that the

feathers nave developed further. Therectricesfire still short, but the

wizss Era nearly adult size. This gives th bird an unbalanced look

when in fli ht. The bill is darker and shorter than in the adult. In

grner l sopezrence the bird looks not unlike an adult black tern

(Chliioni s ni er) in the post-nuptial molt. It does not fly long dis- *
tences or at gre t heights. Young just learning to fly at Bell Island

circled aimlessly at a height 0; aocuc a- feet only to eli ht not itr

I.)

from the scrrtiny place. The win; best wzs slow and not full as in

.J

.‘
,‘4

adult flight. The loose juvenal plume e ms.e them appe‘r larger than

their parents.

.-7b-

 

-77-

a?“

 

Figure 24. A two-day 01d iqterior lees: tern cnick at
dell Island.

 

 

Figure 25. anee interior least tern cnicxs from tne
same nest. Left to rignt tney are approximately one,
two, ana cnree days old.

-78—

 

Figure 2b. .A two-week old interior least tern cnick (est-
ixatea age) at Bell Islana. Note tne cnaracteristic
crescent marks on use Deck Ieatners and tan great lengtn
of bus wing in prooorcion LO tue rest of the body.

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0- «i é 3 E :3 6 7' £3 éidfiiéijmfiiéfiléiéeéfi
Days

Figure 27. Daily weignt increase or interior least tern cnicgs.

Numbers in parentneses indicate number of ynnne averaged

for a given age. question marge indicate tnat age is est-

imated.

-79..

Care of the Young

V

Incipient gerontrl behavior. At nest D where the first young of tee

 

tJrnery netched neither edult was at tke nest wuen tne wriuer first ob-
served tDe new ckick, althouah one wts prob bly present at the tide of
hetchinr Tne aiolts' First reection to the young wee ne; ti e. The
foll win; description of the bah vicr soon after hate 7

is from the author's field notes.

L:- "~ A 1 - .W‘ A \~A -- I» .~ . ~ " ‘,,__ - 1 -\ ... r-r \
53HJ Tue.newlf hetCned yuhu: (ego.t threc .pArS 01; I e tiiate;
reiSes up sad eve; walks a s ort distince around the Left. It

Q

occasionally pens its noutr wide ans cries in a harsh two-note

zopver sparrow's

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werf a u il‘es oe,& 3.3 forth cverneei.

c: . -‘1 n ‘ 4 , , n“ 1. :1

u:,3 f-e iozcle CO”nq to th? nest ..3 our 'n several ::=. iro~

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it, tHen flies awsy. This is reserte

6:30 She elirhts about ix feet from the nest. Until now I have

H

noted no reaction 0 the young to adults or tEeir cell notes,

2
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but new it etug'ers toward the fesele wit}

.1 -‘ , ' r“, ‘ .1 _, - fl ‘ 1
pa o it and stops ed in. one utters s suouuel grii .41, one

after several seconds TLCS to
The young rests about three feet EWHV. Presently the young walks
1

t0 the nest. The fenele calls ”rui Trui and watches tne chick,

I“

es beneath Eer. one raises sligfitly permitting it to

7D

which no

crawl into the scrape. -he soon flies s sin.

The routine is repeated.

 

6:20 The female has brooded for about 12 minutes wien both
adults suddenly seen to "reco;nize" the cnick, eni the sale
cones with an extrenely smell fisln He callarueeiee cui with the
feaule answerii from the nest. He offers the fi n to t'e chick

I .‘J
V

Jed fron beneeth th

fenale in res onse

to

of the adults. T11: chick tes the fish froa the rule end stands
holding it with be u bent cni fie“ cross-wise in the bill, onen
feebly juggles the :oreel and quickly swallows it. The chick

, h p"‘-.-:
tll I: J. C.le1'3.

hurriedly crawls beneath

During t‘ period of observation until 7:2 the aiults

feed the chick five tines, or once every 12 ginutes. The

A

.A'.

.1

wcs enecte. esch time except tnct the chick di not crawl

8

female each time but lay beside h r. On

peeked at the fish and would not eat it.
Fron these observations it WOlld 828” that the sudden

‘-
011'

quent feeding of the young

stinctive incubation reactions to instinctive care of the
eitly a certain amount of "COudlCiOKilé" Ice necesc ry be
553 commenced.

The fenele‘g becaue much less wrry after feeding of t}

The period of wrriness and cnxiousne

divided between two possible reactions (to tHe e_5s or tn
could not be responded to at the 93:3 tine.
The e g shell Wfs not noted in the above nest so that

carried away as soon as the n; hatched. an

you

7

' .
n
n

J.
'4

p

found about 230 feet from .U nest from which

(3'...
VL‘

“1e routine

benerth the

"recognition”

f‘re feelin-
...! A- V 2
e you r . 1:31-11.
4. O '. ,.
Ulu o, ovind

, _ .... _- 1,
Q jottiu) Willow

it wee probcbly

"\
Ur

ell was 1?

"3

Terns ere er psr3ntly able to select the size of fish which they catch.
In feeding the female, the male elwexs brouélt s;;n0Js fro“ one to two
inches long. The young were fed smell fry less than an inch long for
the first few d.ys, then greduslly were 0 ffered lsr r ones.

Brooding gt the nest. Prolonged brooding of the nectlin s takes place

1

only durin: the first f ew de ys sfter hatch -ing--ususlly the firs t two

days. This is because the young beéin to 'ander from the nest, and
except in the extreme hest of mid-day are not orooded dur inD daylight

hours.
The writer experienced much difficulty in keeping the first chickc

J-

in the nests until flue ot‘ei e vs had hatched, so thet studies of

feeding, brooding and growth of chicks could be made. In order to co:-
fine them emporsrily to the nest a smell pen was constructed around the
scrape. This w:s about 6 inches high and about 18 inches square

Palmer (19 41) found this :aet hod useful with comeon terns. The pen was
used with only one nezt, since it was felt that it el‘ored the normal

actions of the birds. The nsturel procedure could thus be observed in

those birds not us filled up, and information could be conveniently

h

0

”eth ered on feedi 1* and brooding activities, since it was obviously im-
practical to follow chicas across the sand with the blind. (See.
29 for an illustration of the pex.)

Perticipotion, behavior, and the broofinr rhytrni. Fi ore 23 3ives a
record of attentiveness of a peir of least terns with three youna, one,
two, nd three days old, respectivel‘. Time spent in brooding by ne

male er ed feiele wis about as in incuo: tion, that is, the female per—

0)
..4
«a.
(D
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(D
I'JT)
, n
O
'1
(....
0

£0 rued most of it. Figure 23 shows that the male's period

Ei brooded restlessly and often made brief GXC‘rS MDT to the wzter or

k...‘

ground the er for no apoureht reason, lCdViné the yoan: uuet en ed.
Usually the gel '9 tot l brooiinq time was only lona enon
female to Fish or bzthe briefly 831 return to the nest. Figure 23 give:
the totel aid average time of broodin; for each parent.

Temper

"0

tures were cool in early morning and late evenin" and t-

1‘
H
(D
,- .
CD
cf»
0
\L

the fee effort to brood the yawn; then, they avoiéed her

, ,. ‘ ‘. . . . “'\ .‘ .. ‘ ~ * . "«‘- A . ' \ 74- l". I‘ '. .. - .
and seent tneir tile SCufrfl‘; zaouu in Uue nest s ea. ,y 0.3o e.i. glue

'u
t
a ‘«.J

n
1.
.1
H.)
O
(D
(+
C0
U
L,
’1
‘ a
k r
C
'3
a:
DJ

egrn to increase (during the first week in July it

. C O .
usually reecned TO to 100 by taut time), and the young beccxe lees
active, seeking Stelter from the sun by crawling beneath the perent.

are 23 3 eye thrt by about 8:#Q brooding be ems cluost coxstant and
cogtinaed into mid—flay. It usually ls ted until nearly desk on the
wcrnest days and continued intermittently through the day on overcast
\ 1“

or cool days of whicn there were very rew. Figure $0 shows a female

to brood. Chicks not brooded during severe temperatures

(3

S
t 0
C
(L:
H
....I
k:
(1‘)
S:
)- OJ

ered greatly, a tho: h the writer noted no deaths directly

13

1

attributcele to heat. As already etrted, while marking and weighiné

young, they occasionally souiht shelter by re min up the obrerver's

“ ‘f
{a Q

trouser leg.

-53-

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costs. us. .8. 13 .5... use: .5... mm “Sauces .1- no I: 739

you a?» on:
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03.393 no: . ‘ . .51. m 533m avenue—um
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a. m
n

 

 

 

 

 

 

 

 

 

      

no:
«83936

~34-

 

v-s .' .L . ( ‘. ,. ° - r ' L L J H ,
regain. at tne nertn its in tue cC e of orCCCi L.n3ii.d in t e nest
#—
O
1 j -. ' 1‘ I.) 11 V ) "J Pu .../‘“" ’
occurred only udrlno tge l-r:t two or t rte szz. Josh cexes p.rCiCi-
r‘ f‘." ‘ ' C 1 V .' p "‘: - I ":‘.C - - ‘ A .0 4 n I" .
D tel Coout e4 ellj in Letulng, out since it N.s cite; i. c Siile to

distinguish positively the MCle fron the fCuC e, x:ct d: t cannot be

prese.r 3i on co W retive pcrticipetion.
It was founi tth in one pCir in 20 :tt-“p ed f63ulfl;9 tnc Cu” occo

:Cle visited the nest y timss, the fgqale ll. Table IV eunnerizes tfle

feedin; activitiss in two pCLrs of terns The first colunn is for tLe
seue period discussed in the section on Incigient parental behcvior.
The second column pre ents fe:dinf data for the sane observation period

i-cussed in tne sectncxlcxi JrOOGlfl" in tne nest.
#—_

(I)

C).

 

It is apgerent that even though the female brooded over three times

as long as the male, she also Cede more at e:3ted feeCin s.

Feeding tine was correlated witi breeztir ti1e. During the early

. m - 'A .0 ”.-., r : - .- . L . n. , _ 0.3 r, .

Corning nours o_ qi‘ct CetCVitj, the yOunq reidsed to Ce led. Tue Clults
"a ,4 C CA - ,1 .- r H “,7 - C: \ .

isle iodr unLucc ul CCCeLXtCC fBLUlJQC out ..eel {./O .n4 c:o3. F101

‘ 9 O J-
I

about 8:33 until 10:35 (the end oi obserVCtion when orooCin; was C cost
because hxuéer lad been satisfied, or in one case becaJse the Cdult
wou d not release the fish to the chick even thoxgb the letter was e; er
to accept it. In the evenins, feeding gr: duClly 3CseC tow rd dusk.

y the second day the chick usually recognized th: parent even bcfore
it came to the nest. TC is WCs probzbly because of the cell note of the
adult, since often the chick Wes beneath tae parent Cti coxli not the
seen tie flying bird. Adults learned to rec: nine t'eir young Ct Cbout

the same tine. When the chick wanierei away in tneir ebxence tney were

able to 50 dir'ctly to it. They never mi took other chicks for their own.

‘ . :. ,- ,. , ‘- ,. - , h a - \, ..-
Acults Were stimulsted to feel by tue actions of tee cnicAs. Several
' v r\ / "" 1' .' ' ~ '1 '— ‘ ‘¢V\ ." ‘7‘ - ~. 1* . h _.. 3 ~ ‘A -°
times a yous, Jlrd was obeerVed to run titn £Uutu open to an .dult whic?
\ -" \D . ‘. ‘.‘. .- .. '.
we a ct or feedinb t.1e

“ut which nevertheless went throu;n t”

had no fish a
click. .u s the stimulation is
brought ecout by the young pecking tn bill of the adult.

all ck'cks received about tre

30 far as the observer could determine,

ssue amount of food. They seldom took more teen they co 1d Get and were

eiin; visits afterwards. Consequently

usually satisfied for several fe
*‘e larger chick night

the aneller chicks got their share, even though on
superior strength.

have bed the food if it hid wanted it, singly tnrough

On some occesions the adult was note to offer the fish to the younsest
this Wrs an attempt on the

1 first. It is difficult to
to distribute the food equally.
In all cases observed feeding was direct, from the adult which bed
fit the fish to the chick. If the chick dropped the food it could

S;

bro
“ Tte adult either continued to pick up the fish and

.J.

not pick it u,
offer it to the young or refused to fee” after the first attempt. If
0 it or, in the case 0

no chick wanted the fish the edult either at-
nele, gave it to the fetele. Rarely, it would keep the fish and fly a
nce only to return and try to feed again. Often this second

7

4

f‘
5

short dist
attempt was successful, even though only seconds had elapsed since the

unsuccessful atte pt.

 

 

 

Figure 29. A pen around a tern nest confines tne cnicks
so tnat tney can be studied. Note nae White ulur 01
an adult 01rd as it sw00ps at tne ooserver.

 

Figure 30. A female interior least tern aligntizg at ner
nest on Bell Island. Note the brood naccn.

h n V'\ - -..\1 a r,
CHIN»; .3 l-AVJn l.

f the pre—flyi

As strted previously, least tern

chicks began to wander from the nest by the second day and usually did

’- ‘-‘
e t:.

+

not r turn ereafoer. Contributing to this we

contrast to the connon tern, adult least terns

only at the nest, but followed them across the

3

1f

tenporary scrapes and feeding then wherever they

8 the
cared

s. -‘.
sent,

fact that, in

for the chicns no

brooding them in

_' ...‘.. ‘
Ifllbut 08.

Hoser (1943) noted in observations of the interior race at Omaha,

o
G

Ifebras”i,

seen running across the sand in Bone n fibers, and bh
excursions within 43 hours after hatching.

that from a distance with a f eld glass the young could be

a

on

at Bell Island the chidis at times seemed to have a very definite
destination in mind after leaving the scrape. Those in nests nerr the
middle of the bar neerly always headed for the la oon side of the torn
while those in nests near the nainstrecn side of the bar always ran to
thft shore.

The a‘ults, although they seeded distressed at these wa.derinés,

. .L
prevent he

' 'I 'n “ a L
:10: e Lin-7.013 to

observer twice

8 aw

a parent oir

evidently trying to sake a chick lie still. The adult alighted beside
the young bird which was scurrying across the sand, and seizing the
chick in its bill hurled it to the 5.0und. The chick apperred to be
dead, but no sooner had the adult departed than it was up and runnino
again.

No exact data could be obtained on feeding and brooding fron the
rather confused situation resulting from these wanderinys, but in gone
it can be said that both activities were irreyular, since as often as

a g " ‘L «a ' x 4-"
._,Cv~ ._: «Dr 1:1 U111.

the three chicks in a nest would

1..

so that the adults were kept tryin

1“
J

ee d

; that;

...an

rent directions

to care for then at all.

t

rel

not

A harmful result of nis nest des ertion was the resultant ne 31s ct

of er=s still rene ining in the nest. As lon- as th e youn 3 remained in

QLJ

the nest the e*'s still not hatched continued to receive incubation.

43.2.;

‘

Yet once the interest of the adults in the chicks nad been aroused cney

see=.ned to ne3lect any remeinin3 ev~o and never resuded incubation once

1 ‘

the first born chicks had deserted the scrape. Tne writer note d severel

C

sin le ezgs in the terner wnichp i ailed to hatch for *his reason. On
J (its

openin3 then they proved to have dead embryos not more than two ua’S

frofx hatc.i.g.

(0

he be3innin3 of the fli3h stage most of

(f‘

Ddrin3 the week previou to
the chicks which rel survived after desertin3 he nest had 3athered on

the shelf of the Sell I land bar neer its outer end. Here they could

be found crouched ’etaeen pieces of driftdood or under th leaves of a
few sazll hezbs which 3rew there. They were fed here until able to fl‘.

TABLE IV.
Al. T50 :3 £5 #8 o

A sum-w! 0a mzwlrza AC‘PIVI this

 

 

 

Age of Nestlingfi 3 hr. 1,2, ana 3 days.
Period of Observation 5 b5-7:20 n.m. 7:3n-l?:U5 a.m.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1 nr. 35 min.) (1 hr. 15 mix.):
7 4 1 ‘I
to. of Nestlgfigs ; 3 1
Total feeding visits 5 VP
_,‘ __._-_-,_-____*___;__ _-
Average no¢ fiasdin;
visits/mt. 3.15 6.1
_. -..... .... L__ ._ .__ _ _
N“. succesgful feedings 'h 12
Average successful
feedings/hr. 2.52 3.6 :
l
__J- , ;
No. intarvala between i
BICCGBSfUl feedings 3 12 1
!

 

Average length of interval

3 plus min.

 

 

 

Extreme. 2-5 min. l-UW mine
Feeding attempts by

(assumed)'nale 5 (all) 9
(assumed) female * 11

 

 

 

 

_-__ ____.-.

 

A‘A

DECRT ALI TY In . 3 LC: SEVI TY

mortality in least terns is extremely hléh up to the fl

{L

Hagar (1957) -t:te

(3

that in a colony of 423 nests in Massecnusetts,
308 (72 per cent) were lost before hatching. Cf the 820 e553 only
212 (26 per cent) hatched. Cf these 212 chicks, 75 reached flying
steée, a survi 31 of only 9 per cent.

At Bell Island during the 1955 season, mortality was even ni
with only two young positively known to have reached flying stare. Tne
approximate surviv 1 rate res estimated by the writer as follows.
Assun'ng hat the colony contained 50 nests, there was a potential of

.L

In seven nests under close.cbservetion 15 cf 23 ere:

notched ( 65 per cent). Applying this percentage to the colony as a
whole, approximately 55 young should have been hatched. During the
pre-flying juvmfiel phase (the third week in July) 8 young were known
to be alive. Yet, on July 21 only 2 could be found, and these were
both flying birds. Several hours watchiné from the blind and a
thorough search of the bar revealed no other chicks, and it is believed
tnet there were none. This is a survival of only 1.7 per cent.
Apparently the season was an unusual one. At one period, between
July 5 and 8, all the chidks bunlcd from the ne ts under obserVution
disappeared. The cause of their disaooecrsnce is not kROWu.

A.

Longevity

Hiéh mortality in the nutcl and juVenal ELJéUC is bulenced by a low
. . . . . -,~y . n _. . _ _ V. ,.
mortality in adult terns. Tomgins (ly;+) in ucOréla recorded a lU-yegr

~old least tern bended in l92§ and recovered in 195,. The Murplee (193%),

assuming that tne least tern in England lived on average of five yours
(no exact reason given for this essuuption), and tnct they laid an

v e t" r w- .' u * ‘ ‘ I] w. y“ 1 s A v " r~ ~ ‘ ‘ {, p « f“
avert-e of 2.u elzs (iveroge Cl nauy clutches), reusoneo tact s is ale

6.)" e3,»
tern laid 11 eggs during her life. Only two of these would have to
hatch to maintain the species. Thus, a mortality of over 70 per cent
could be tolerated.

Causal Factors
Causes of uortolity at Bell Island have been uentioned in many
sections, but to susmarize hey prob bly
included infertility of the eu.i desertion of the eggs resulting from
the first hatched cnicks leavin the nest, parental neélect, exgosure

to the sun, and predation. In many colonies floods take a heavy toll,

especially on the low bars in the plains area. It was inyossible

(D
(+-
:3:
(D
"I
(D
rJ
'gl.
g...“
<
(D
Flo
L
o
"S
I

in the short tine spent in this study to deteruin

tance of these factors, but parental neglect seemed to be a basic one.

A

" ,‘ ‘.'-""'.’f "‘ '7‘ ". "L" '~:"T' ”T” C’“T‘ .‘ '3 4' ”,"AL 37L" ‘,‘\T )3
.‘IALIILL‘A-i; LL - ”LJJ NJ. u: 2.1.“, J.L {Builds an“ .L»'.L.J.J

Unlike otner closely related species, the lSCSt tern characteristical-
ly nests only in homogeneous groups, even when other species are n~stin5
in the same region. However, tre interior least tern in sons cases

nests witn the piping plover (Charsdrius telodus) and the an

O
‘6
*U

H

O

<.'

(I

'1

 

(Cherccrius alexandrinus). The former is an associate of the tern in

 

flebraska, the latter in northwestern Oklahoma where the two can be
found nesting on the salt flats.
1 L" ‘ \ -~ _ _ ‘ , n 0 ~
Moser (lQeQ) StLteS tnat least terns and pining plovers, altnough

'roups within a large area of sand, in 1943

:3

usually nesting in separate
used the same site because of encroaching vegetation on a part of the

bar. Wycoff StLtGS that at Lexington, Hebraska, he has foand terns

nesting with the plovers, but that the nests are usually separat

because the terns prefer finer sand and gravel than the plovcrs.
At Bell Island no other species nested on the bar. The most conson

0
1n
*

v.’

‘ria riparia)

' "I
{p

species frequenting the bar was the bank swallow (

 

which came to feed on insects on the sand in flocks of as many as 150

1"

birds from a colony 0i per1a~s 230 pairs which nested in a larée clay
bank directly Opposite Bell Island on the Kentucky side. Other species

wnicm occasionally entered the ternery were the killdeer (Chara rius

 

vociferus and kingbird Tvrannus tvrsnnus . The terns for the most
A.) _.I4 44

 

part ignored these visitors even thouéh the bank swallows occasionally
landed in great swarns among the tern nests in search of suall beetles.
A tern was nce observed to chase a kingbird which ventured too near its

ne 7t.

Predators

Rats are frequent predators in common tern colonies alon 3 coastal
regions (Austin, 1945), as are various species of 3Lxlls and jae3crs.
Bartsch (Sgrunt,194o) observed youn3 le act terns bein3 mutilated by
having the ir win3 s clipped off by sand—crass At Bell island no pre-
dation was ever actually observed, yet instances of e: 8 missing from
nests overni3ht and the mutilated bodies of several cnicks, on one of
which only the le. 3s remain ed, seeded to indicate that some predation
existed. Host prooa21e predators were tne crow,,black vulture (Cererycs

stratus), turkey vulture, and the black-crowned ni3ht heron (chticorex

 

nycticorax). Judgin3 from the actions of the terns toward the first

 

three, they were predaceous on the ternery. The heron probably was a
ni3ht visitor to the colony. Marsl;a ll (1)42) ste tes that this species
eats the e333 in common tern colonies on western Lake Erie at ni3ht.
At 3811 Island the Species was not connon, but on savorel evenin'
just before da hness two or three of then frequently car. to the shore
of the sandbar to feed. The writer once observed an opossum walking
alon3 the beach. ther ma duals may have been present but their tracks
were never seen in the ternery. he vultures loitered along the beach
during the day and occasionally flew low over the ternery. They were
never seen to ali3ht near the nests, although on one occasion one did
perch on a log near the ed3e of the ternery and seemed to be searchin3
for something, all tee while oein3 "bog b: rded" by the terns.

Relations with Man

The least tern is of little economic inportance in most of its range.

HoweVer, Gates reported that at a fish

.eorasaa, the birds are shot because they feed on the anal fish in
rearing ponds. At Bell Island the.birds are little known by the nat‘ves
who refer to them as "minner hawks," in reference to their feeding

0 ‘ ‘_ D
18.0 t8.

SCCIflL ACTIVITIES

Fien1n3

\

At Bell Island least terns fished alnoc+ en irely in tne shallow

littoral waters of the bar which were priaarily on the mainstream side
and 'n the mud-flat point area. There Wrs some feedin3 in the quiet
waters of the lzfoon and in the shallow pools on the islan upstream
from the l<3oon.

They often fed in small loose groups of two to four birls but never
in he ler3e flocks characteristic of coastal terns. This was probably

I3 ' 1

because the food LlSJGS did not travel in such lmr3e schools as do
a least tern hovered frog a few fe t to as such as

10 feet above the water, seldom hi her. If the prey was si3htei the
bird quickly plunged to the surface, usually breakin3 its fall just
before reaching the water so thrt instead of divin3 beneath the surface

it only psrtiallv subxer ed. At tines instead of ne co:plete plunge

la NJ

'I

it cane down in a series of alternatin3 snort dives and hoVerin3s as
if not sure of its tar et. The final dive oft,n occurred free no sore
than a few inches Ebove the water.

V ‘ ' ..
3311111

(.0
L.
O
f D
< D
..)
(0
Po
:5
H.)

V- '3 a
o ‘ ' a;

.. J. ~,L ‘ 4 - ' . z , , ”‘3'.“ L...“ . ' ‘n P',,‘.. ,.- «~.— ,
the neso and returned in two or three Minutes wit» a lien and reps ted

f)
0
C7
‘3
“1
<
C.
‘44

this perforgance several tines in quick order. Yet bird—

(3;

a)
r.
h;
.0.
i '0
’— o
(B

slog; the river would ofte. iv
success.
Althou‘b in many re3ions interior least terns frequent necrby lakes

,—.A
s—J

for food (Coffey), at Bell Island this was not the case. The biris

f
49?-

. F‘L 1 x‘ Q 18 .‘ - ‘~ ‘N n ’) ,yg q I“ r‘\ ,3... 7-”. I, ’1 A
occurred 1J1 scsctered inluDelS us fld'tlssticeiiauc'tue us or (“ml or tee
. r‘“ I“ ‘W ‘ fl "‘ ‘ ‘.‘ ' p" “‘N V ‘ . "' I’ V . f: " ‘1 . v C O '
isleuc, cut not oeyonu. isey were llACdlve not of regulsr occurreice

in the Shawneetown sres only 3 nil downstream.

w

Defense and Fear Reactions
An upfliéht was the isuediste reaction to disturbance in tne ternery.

Tkis occurred at so sli

, )
(+-
m

'0

rovocstion that it often took place three

.4

or four ciues in a scsce of five mixutes. Psluer (1941) divides these

two were observed at Bell Island.

1‘ '\ m,‘ ’ I 3- ‘Vr 4' v ‘. "
Alarns, Lnfifie were tee dose coseoa ty

J
(D

of upfligbts at Bell

*r

 

Island and SGEle to have the least element of fesr in them. Alarms

)4
F4
(1'
r!
I
p.)

varied muss in intensity from fli”hts of only a few terns res;

O

eru a migcr disturbance such 99 a boat on the river, to flight of all

terns most cosuonly caused by an si= vulture, crow, or human.

At the spprosch of a river bout the fli5ht was apperettly bases on
' ' - ~a ‘ ' —r‘ A - vv -~. -
curiosity rather tr1 fee; The 31rds took off csl.lJ, utteridé a

short kio, his call. They then flew out over the river, occasionally
following the vessel for a short distsnce. They were never seen to

' . L. .. O _‘ .1-
in t e;e Lllfuts.

p.

p
3.99

and usually all mesbers of the colony participated. After sll terns

A

5

were in the air the ‘ethered in a flock Rld ilew above the intruder,

attacking in groups of two or three in a well organised and continuous
erTEJG. They never seemed to strike the oird and always gave up the

chase near the edge of the ternery or slightly bevond. In the e attacks

the terms kept up a constant chatteriné.

Whereas the attack on a crow or vulture see ed to Contein uixed

elements of 'exciteient of tee 0% se and au5er, the attack on a human

1

was one of total and extreme anger in which the birds hevereo over tLe

victim uttering e . Mrp .-_ -kea-kek. This coll—note ceased in the dive

 

and was replaced by a ha sh zneer as the bird swooped neir. The terms
never struck but often defeceted on the ooserver in there attacgs.
Defense reactions beceqe more intense after the youe5 hitched. After
Jul\ 5 wken the Electzct drop occurred in the population, r;ci:l attache
dininished age all intruders we re i

cred except when they were close to

00‘

a CE.iCL‘:.

.5 , \ r'1' J- o - 1 xi ‘ “.4. .
Jr3udc. lud FMJCCH acvegt el dun5er, sucn es the eorupt at: esrance

of the observer fro: the olind, precipiteted these flights. The de—

parture was hurried and silent towcrd the water. The sirds never rose

hth in the air until they

("J

*1

eached the water where they gathered in a
flock and returned to defend the ter nery.

All defense “cactions ceased e the outer extrexities of tee ternery.
Ho alarm resulted free other birds or tthoe along the beach or on the

in these

J
O
P
C

B
F
(

l’

.—
(‘f’
b
C»
i
6
K...
H
(D
re
d”
C”
b
.3
(“

0
P
k
(D
"2
CD
cf.
, J
C
L3
4
(u

1)
(D
C

Le
(I
,

‘xction to Injured Terms

Olly Ozie ooservetion wss 2;;e of the reactioxi of terms to an injured
fellow. A feaele torn was unable to fly Cnd fluttered slog? the buech.
Approxinatcly 10 other terse flew OVer her.
the observer to hevr their calls. Tue soon beooa to dive at her in
much the same Jenner thct they led e gloyed witn the crows and vultures.
Later the writer found the bird dead. The exact cause 0: dectn was not

noticeable in :n autop m3 lner (13“1) stetes tLot in cocron ttu'rs

if the injurei bird is eufoebled and snows no blood in the plumage,
tYe other terms merely fly over it. If blood is visible, they ”ttack.

The least tern was attacked even though there wee no blood visible on

5 V r - .q -\ 4- ‘ . ‘ ‘ {-VL‘ .P - ‘ 7‘ ‘4 .' ("y . I 9 ‘
Least tar s Wuose nests nave been Qescroyeu uo not ieioin in tee

Islend there was a correeoondinr reduction in the nusber of adults.
Belore this disaster 3 vulture flying over the ternery usually attracted
betWeen 5F and 6” birds to the eitecg. Later the sage bird was paraded
by only 5 to 15 birds. Other terms were present in the area hut they
did not join in the attack, probably because they had either 10;» or
had never had social ti:s with the Bell Island ternery. The nunbcr of
terns in the ternery decreased to two adults on July 27, and thee were
present for only a few minutes durins a three-hour period. KO 0
terms are seen in the entire area thot day.

1

Departure from tee ternery varies widely according to the season and

the area under observation. Stiles (1939) stated that least terms in

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POST-33335133 ACTIVITIJS

V

When the ounfi are sole to fl* for sus+aincd teriods the desert the

Y o J l
ternery an in company with the adults wander along the rivers sad lease
for several weeks before niérstion. (For the extent of these wonderinés
see the section on distribution.) In these nomadic movements they cgn
ften be found associating with other terns, sandpipers, and plovers.
On Au;ust 50, 1955, the writer saw a flock of about 20 birds, both adu ts

and young, at Bell Island. These were obviously not birds raised there

re young-of-the—year. Similar flocks were

(0
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noted at the Carbondale Reservoir, a shallow lake in Jackson County,
Illinois, from late Au; st to mid-September, Though all thege young
were able to fly they were not adept at fishing. They followed the
adults about and were fed occasionally by them. The feeding always

around. Rarely did they dive for fish and then

b

took place on the
awkwardly end without success. This feeding of the young by the HQUltS
indicates that the birds may migrate in fanily droups at least during the
early part of fall. whether members of a colony renoin t05etner is not

known.

",,.._| . ..., n E-,‘.I..,., .....r,
-)JA'L.'A‘“O.JLY 4h. A) DC‘t'ULJu-II we: .)

This study of the interior lesst er "ts rna albifrons s*”“lc

"
l,. I.
-~ u.-‘ -k.-

(D

CS

Burleigh and Lowery) was divided into

(+-

hree parts: (1) An actual field

study of a colony of these birds at Bell Island in the Ohio River mode

during the summer of 1353 from June to September; (2) an analysis of all

available inforaation in published literature; and (j ) corrosionisqce

with ornithclo ists throu bout the range of tzze subspecies.

Tne interior le.-st tern ran.;s in su:iser from Baton Rouge, Louisiana,

‘ .-. . I.’ .. ~.
north and west on tne hissisSippi River System to Indiana, estern Iowa,

South Dakota, WI onin , Kane as, and Oklahoma. Foreerly it occurred in

north.c we traland ea wt rn Iowa, and in eastern Nontana.

Migration begins on the Gulf of Mexico coast in April. Terns, follow-

ing the river, reac chississippi "nd Ten;essce in late April and early

May, and by late may have appeared in Iowa and in the plains states

' 0

Son e e rly records in Leoreska and Oklanoxs inlic te that cross-country

migration occurs.

Af er the n eating season least terns wands up the Ohio 3: er as

far as the Falls of the Ohio at Louisville, Kentucky, with single records

from Ohio and Wisconsin.

Fall migration be5ins in late August and earlyo Sept saber. Few terns

linger past t1.e second week in Scott nber in tie north. October records

are occasional from the lower Kississippi River. Sons winter in Louisi-

ana and along the coast.

The presence of sandbars, t: e existence of favorable water levels,

and the availibility of food are the three most intortant factors in the

occurrence of the least tern on the rivers.

-102—

Sandbtrs are formed when a stress reaches grade level, at the mouths
of tributary StrGFIES ard in the plains area VTen su;::;er droub‘ hts occur.

Isola.tir n, height of the bar above we ter and duration of the bar are

important.

‘

From the information available it spears that the beginning of t;e

breeding season is definitely governed by the spring flood conditions.

Flood waters usually subside in June so t at nestin begins soon after.

0

Severe floods may prevent nesting or delay it until July and August.

It is sible that over t3f1e year he regula r delay in nec- ting has
caused a physiological adaptation so that nestin: would be late re er rd-

lecs of flood.

Conditions favorable to sani‘ocr formation also favor shallow waters
where an souidence of minnows is available to the terns. Interior leas
terns probably feed almost entirely on minnows. At Bell Island the

do.3inant foodf ish was probably tz1e river s ;i11er CCo ropis blennius).

 

Sand surface te peraturs s are conside ably higher than air taggers-
tures. At Bell Isle nd tr.ey con nonly exceeded 1000 F. Such temperatures
require that the e558 be shielded from the sun since optimum incubation
temperature for most birds is about 950. The young suffered from these
excessive te::1peratures, but no deaths were directly at tribut ble to
heat.

V

ne breeding cycles of nearly all terns in a colonv are synchronized
1

by flood conditiozs. By the time bars are exposed practically all terns

are in 'tr e breedinr area and thus c01:nence breedinr activities at the

Cour ship of the least tern is sinilar to that described

terns except that the fish fli“ht i; not so oroninent. It consists or

0
:3
(L
”3
C‘”

the aerial élide, posturing, parade, copulation, au~ incipient
-buildin5. Courtship rarely takes place in the terrier"r except for tn*
last phase.

The size of interior least tern colonies ranges fron a few to as
many as 30 pairs. Snell colonies are the rule on the s;eller streags
in the plains area and in the north; larger colonies are found on the
nississio 1 River. The Bell Island ternery of approximately 30 pairs
is the largest reported.

Interior least terns usually do not nest in connect groups. At Bell
Island ufiG nest area was about 120 acres, the dens;ty 0.7 nests per
acre. The birds usually nest some distance fron the water on the
highest part of the bar.

V

Because of the relatively great distance oetween nests territorial

‘

eleom occur in the colonies.

D.
(D

t +
iSD'J‘ VBS

Nest-‘ouiliin'~ is initiated by scrape-making. Tne nest is only a

d

shallow depreSSion in the sand or gravel. Scrapes ere usei not only
for the egcs and newly hatched chicks out are constructed for temoerary
of chicks which leave the nest.

3 51.2 X 25.8 mm. and are buff or olive buff speckled

with brown and grew. The size of the clutch varies in enersl frem two

J.

\

V -\ 1 u‘ ‘ . -
ly Penna. At dell Islcni asout e3 per cent of the clutcnee containei
three eff? 20 per csnt two. The eg;s are prob sly lai? on succes:ive

days. This belief is supported by the fact thct at Bell Island the

young always hatched on successive d ys. Apparent infertility of eggs
I 7 ‘L f
at the island was aacuc 3.0 per cent.
Althcudh there has been diseéreeaent concernind the length of the

s in the south to three in the north. One to Four 9? c ere occr~ianv.

—l .\7'-_

incubatio‘ period, it is now considered to be aocut 20 days. This was
in agreemsnt :ith probable seoi:1nin of nestle: at Bell Islani (sown
after the flood utters subsided) and tie fi“st hatching.

Participation in incubation by the adults varied in different pairs

In SOLS it was equal, in others the flu-l performed aliost all incu-
bati,. and was fe by the sale or relieved by him for nor periods.
Hatchin¢ at '11 Island bcsfn June 33 and the arezter part of it
occur rred in tTe week following TLe young are covered di h yello or
buff-8 itscd dc 3, Gal wtiéh about 5 5rane. They are able to walk tn

first week. Wei ht at

5.)

this tine is about 15 g-‘r:is. At the :03 cf two weeks the juvenal
pluqeée is nearly couplets excegt for the tail. The color is new Luff
and gray shading to elite on the uluobo

The chic k flies at about 23 days. At tfiis gericd tze pluiaée is
no much one an ged free the two—neeK—old biri.

Uith the first };stcned young the parents instinctively switch frcn
incubation to brooding and feeding. Breeding is primarily by the fenale,
the sale elievin* her for short i.tervals. Feeding is carr led out oy

4.
v

4".

Cs

both biris. Both c ivities are most ;

day. rly in the earning and late

H I

and refuse broodin and feedins.

given to the yoxng at first.

once fed is usually satis

CL

SI}:

revalent during the heat of the
the eve 1in5 the chicks are :ctive
n; is direct .ni only v v ssall

. -1 x. ;...‘r ‘t”""+'“‘
Liaveab 0.1M»,- ( UJLLUly’n,

fie for seve :1 R ding visits
in and prior to the ire—rlvin
ted to infertility of the ed .,

, A
-.-.c‘cJ-

g

desertion of the egys resulting from the psrents cerin5 for the first

born youn which usually left the nest on tae second day, perent l

N.
1"
C)

neglect of the young, exyosure to the sun, and predation. In sose
regions, sepecially the plains srees, flesh floods take a heavy toll.

At Bell ISlend the terns fished in the shallow waters neer the bar.
Tne birds seldon hovered over ten feet above the water in search of
prey. The dive was either continuous or in a series of short plunges.
They never congletely submerged in categ'

Least terns usually nest spsrt from other Species; however, they have

1

seen reported nesting with pipin5 plovers in ;eoresks end snowy plovers
in Oklahoos. At Bell Island no other Species nested on the bar.

Bonk swallows, killdeer, and kinstirds plus probable predators such
as the crow, turkey vulture, bleak vulture, and black-crowned night

heron wer requont visitors near or in the Dell islend ternery.

CD

Althougn classed as probetle predators, the last four species were never

Interior least terns are of little economic inportsnce to men.

However, they are snot as e nuiscnce at a fish hat nery near Kortn

Defense and fear reactions could be classified as slsrns or dreads
(Palmer, 1941). The birds attacked all crows, vultures, and humons
entering the colony. They were also put to flight by boats on the river.
Reaction to an injured tern was to attack it in a manner Sifiilur to the
attack on a predator.

Deperture fron the ternery is gradual. Torns whose nests were d¢_~

stroyed left the colony promptly. At Bell Island tre colony was all but

-ioé-

deserted by the last week in July.

After leaving the ternery interior loact terns wander along the rivers
and lakes associating with other shore birle. The young are fed b] the
adilts dur'ng these oovenents. This indicates thet family Drouge oey

uiérete together.

LITEKATJAS C FLO

JEkOtC. AJL, 2:275—279.

O)
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Az‘zoriyL-uou s

1953 Twenty-five yeor seinery of bird mi5ration in Hebrtsku,
pcrt °, 51118 to cuckooe 3931. 31rd Rev., 21:13—13.

 

Austin, 0. L.
1934 The :tgtus of Cape Cod terns in 1934. Bird—B'Ldinf,

 

 

1933 30m; results fro: adult tern trs;pin; in toe Cape Cod
colonies. Bird—3 n‘in , 9:12- 25.
i a - a \
19%7 A 8+u y of the mitin5o of tne common tern (:tern' E ”lrJJTO).
Bird-Brniin5, 15:1—10.

 

1" .- r o _ r‘ o _ t o O ‘.. _‘ _ . ,‘ _“ r-~
194) L te tendClty, e behaVlOF tralt o- tne com on tern (Jt??u

hir 32:30 Liin.). 3ird—33ndin5, 20:1—40.

 

Austin, 0. L., Jr.
1929 Contributions to the knowled~e of the Cape C i
Bull. Lortheestern Biri- 3: H51 Acsn., 5:125-140.

 

Bertsch, P.
1932 Some torn notes. Auk, 59:131.

Be nckes er, H. R.
1943 OtCS fron Brule. Neor. Bird Rev., 16:94—96.

 

Bennitt, R.
19§2 Check—list of the bird: of Missouri. U. of Kissonri
Q
731—v1

StuilcC,

 

Bent, A. C.
1921 Llfe histories of North AmeriCun 5u1ls end terns.
U.S. Te . Mme. Bull., 113:1-540.

 

.Beyer, 3. E.
1907 List of the oiris of Louisiana, pert iii. Auk, 19:,14-521.

Burleigh, T. D. and G. Lowery Jr.

1942 An inle nd rfice of 2-3r22 :lbif r0213. Ccc. Eeiere Mas. Zool.
(La. 3U. UliiVo), 10:1‘71—11770

 

Esutler, A. N.

[-7 AI :5 - I- ‘- ' f‘ T . .. ' v'.‘ . ‘1 ~:‘ r- ' ,3 . 4 s; " \ '-
luyd Tue air 8 oi i.d sis. Report oi gtste Jeolo5lst, lo;7:SlD-

 

i i
1137. Indiinfiuolis.

l;\

.._
— -
\JH'

fir.
VCABP

l, L.
l e

e1 1.
34 L est torn taken ngrr Toledo, Clio. ink, ;;:37.

V)(J

001lifl‘e,fi. E.
1929 An inve ti*Fti‘n of the food 0' trrns :t Jlek"
Point, Joriolk. Trans. ”0' ' ' ' t

3
Q SOC.’ 121/5-520

 

Coues, 3.

 

1374 Birds of the northwest. Vest. I.ter1or, U.S.3.S. Torrit.
Viscel. Puo., 5:692—696.

 

Dumont, P. A.
1993 A rev ed list of the biris of Iowa. Univ. long Stu:'
1 t Ulct., 15:1— 171.

 

,
-O Breedin5 of the luhfit tern on the Mississippi River. fiils.
3311., 42:133-137.

r
’
1937a The e stern lee t tern breedin5 i1 Thu rston County.
e-DI‘. Bird .2563V. , 5:9.

 

1977b The eestern tern breedin5 in Bur t oount . Kobr. Biro
38V., 5:110.

 

heelcer, F. N. and fl. Mooer.
19w5 Check-list of the oirls of LebrPSCe. Nebr. Bird Rev.,
(reprinted aid revised Lov. l‘“5), P. lo.

 

855531“, J. J56.
1937 Least tern eta liG€--1935 end 1925. 3311. “$39. Add. 300.,
21:5-3.

 

Hairlez’ac)-ls, L. D.
1945 Nesting of the pipin5 plover aii lee t torn in Cass Cointy.
Keir. Bird Rev., ll:

 

Hudson, G.
1939 Some ornitholo5iccl results of E six-week collecting trip
a ‘ fl . 9.‘ ~ ‘ ~~ ‘ ' ‘ '
along tno Bounceries of aeorosam. neor. Bird Rov., 734-7.

Johnson, R. 23’.
1936 Bird mi5ration at Dubuque. Iowa Bird Life, 6:3-9.

 

Jung, C. S.
1931* CCCdrreHCe 0:3 t‘pe 18‘: fit tern ((‘L. m8 8. 8.7-ltill’.‘r‘\lul) in
Wisconsin. Auk, 52: 370

' fl
4 .
I . Q

Q
A". o I ‘ ‘ ' '\ ,A Q' u,"
l9)0 date r birds in a dry lens. #118. onll., Laz‘o—ws.

 

-131-

Lon 5, 1". S. '
1953 Chec k-liot of Ksns qxs biris. Trffg. K’HSRB ACPd- 3C1: “CC:

43: :7 45 .

,/

 

Msbbett, s.
1890 A query in FOSTTd to tre leest tern. Auk, 7:413—411.

 

Mzrples, G. ani A.
1934 Se te n3 or sea s~1llows. London: Cogntrg Life Press,
1. 27.1

hell, K. ‘
1943 Eight deoertion by n3.tin3 coagcn terns. Vile, Bull.,
51" orig-)1.

 

MCCr:ury, O.

34 Th Platte diver es s migration route for birls. Eebr.

Bird Rev., 2:38—59.

Brown' 5 least tern. Proc. Biol. Soc. Wash., 19:71.

 

 

Moser, R. A. .
‘.‘., ‘ - . . . -
1993 Tne pipin: plover end least tern nestin$ in Cache. hzor.
Bird Aev., 8:92-9fi.

 

 

v . . .
1945 m1 oitional not_e on tr: fleeting of tqe Jipino plov,i -t
C‘ “6'31“. Bis-1‘ Arm, 1111.6
-\lC‘., ‘2. ‘1.
19:1 The birds 03 Oklah393° Univ. CH1°WC29 Png. Biol. Surv.s
531‘3-2- U. 0? ChlahoAa Press.

110 l zan , V.
1953 A su1zary of the wuixer 3e

V r‘

3.05“
- -- "I ,, .. , - f?) ") ..\
r‘_fé;orl). “U1. L'i\;1l\1 A.Ct :F:6:IT._3‘+—C.'_JJ.

 

 

1955 A Siamery of the fall A15: tion (in the midJle western rawrie
region). A... Fiili gotss, 7:18—20.

 

 

Cbe holser, H.
127:5 T‘rie b.

 

_ ’

A
U.
rd life of Louisiana. ju11.L‘. Bert. Center'. with
est. A ric. Biol. 311v., 2Q:2;\-Q¢u.

"1 ' 1 .0 -,-1_ . '1 1 n '“_ ‘.. 1, Mi 1 ...: '7,-.L "' "A
19_J. Biras oi whit D4A01£g ouil. -u h -o-1 -nnai. a”. -u;o. “its.
* —

 

r\

1“,. ;" L.‘
Dylc.’ y:"fk‘.

 

 

~110-

01,11 C. 8., Jr.
9 Hi? Cry of one sun“red newt? o: are

.1

3:? A ;uide to oiri finding (west of the 3'
foori U. Frees. 1-739.

PTPCJQF, N. E

O
‘3‘:- ' r~ . ‘ n ‘ '- “ ... . ‘ r» r‘ . ( :- C '—>-/
1943 The blrab of tue JO doxucs 1 plwu. Ann, 42: ~,Z—A- .

Spruut, 5., Jr.
19HS The term coloni3€ of the dr Tor+ mags Keys. Auk, 63:1-19.
19;9 T.e lea 2t tern in Iowa. Iowa Bird Life, 9:19-25.

 

Tout, Tl.
1934 Wq+er—bird conccntrstions due to irou;ht. Nebr. 31rd Rev.,

II
2-::~
O U.

 

’ , ‘2 ‘-“ V ‘0 . ' v ‘ 1: ~ ~ ‘u. r' ..1.‘ V!" f ’(f\
1)47 L*ucoln Couztr alrié. Pao. p;*vz 3:1} 3y uuuior. :p.Q7-u9.
' ‘ 2‘ 1‘"
Vlsnar, a. a.
A a“ . ‘0 ‘ ‘ . . o r‘V a 'V‘J'V 'W’L‘“ ,r“.- 3 4L1». vhf-‘7'— .,.
1914 A llst 0; tie Sires 0L Olaf pomuuf, souug6L_t,rn ou,. ,,&otg.
' " fi".7)’1

 

 

=rds bS(-r wqtd nerr Hinco, Ce:fi mr l Ckluho;g. ItLIC. 3411.,

Vlt"C’ru H. F.
1921 The Manugock of British birds. Vol. V:l-§56. H. F. and 3.
fiitherby Lti., London.

'Jorth, C. B.
1524 O ’Pi‘g volguae E;

.J

.JQ

‘ ‘ o a — I I r
a inCUDCthH parloJS. at, 37:44-60.

tnt-fCOff, R. 3.
~. — . . . - ... . ‘ f. “3‘ :-
19;O untltled. L€"F. sir; ACV., 19:;y—QL.

 

~111-

‘f

oan§wcrth, H.
19:0 Brefldin; of tha 13: t term in Iowa. Jilr.

 

732' 1, hr ,— ‘» ,F-~ ‘ 2“ r: . ‘J. _ _‘ a " fl - ‘ J. 1
7/1 Tae :mKfl‘ c~1 3 get a uliLesrb Lara 14 ‘wuzfll

1932 Field notcs frc: Sioux Citj, Iowa.

7'? a" a. y“ ‘ z N" '-“L . ’ ‘ 1“ 7:1 u ". v 1' . qu
19/) 3:21 11153 1.113;;1141011 Gut/OS 11‘011 .310 3. Cl 9", Ion.
2.78
/ '/ ’0

 

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