A POPULATION SURVEY OF THE RING-NECKED PHEASANT IN MICHIGAN Thesis for the Degree of Ph. D. MICHIGAN STATE UNIVERSITY RALPH AUSTIN MacMULLAN 1 9 6 O I N \W N l“ “W \\ NW NW 3 1293 10237 2228 L This is to certify that the thesis entitled A Population Survey of the Ring-necked Pheasant in Michigan presented by Ralph A. MacMullan has been accepted towards fulfillment of the requirements for '6' '7" oluuu g Rudd“. ajo‘ professor Dm May 20, 1960 ' LIBRARY Michigan State University CUNOING 9 ma 8. sons . BLIOIEAKQELNDER! ‘ REMOTE STORAGE PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. DATE DUE DATE DUE DATE DUE 2/17 203 Blue FORN S/DateDueForms_2017.indd — p95 A POPULATION SURVEY OF THE RING-NECKED PHEASANT IN MICHIGAN BY Ralph Anitin Macttullan AN ABSTRACT Submitted to the School for Advanced Graduate Studiea of Michigan State Univeraity of Agriculture and Applied Science in partial fulfillment of the requirement. for the degree of motor or PHILOSOPHY Deparmnent of Zoology 1960 e 7' ; M- Approved #:‘z—K s11) e. I /U 4(( n Cg_‘ 7 ./ ABSTRACT This study of Michigan's pheasants from the standpoint of popu- lation dynamics had three objectives--(l) to reconstruct a history of past populations, (2) to acquire information on current population levels, and (3) to devise better sampling methods, when needed, for obtaining that information. The study was made chiefly during the years 1947-1950, but data were collected each year thereafter through 1956. The work was sponsored by Federal Aid in Wildlife Restoration Project, Michigan 38-R. Although a number of private releases were made beginning in 1895, pheasants were not established until after 1918 when the State began a release program. Pheasants were well established by the early 1920's and the first pheasant open season for hunting was held in 1925. Reports from hunters were the best source of information prior to this study. The State's computed kill based on compulsory hunter reports was determined to be a good index to fall populations. Pheasant distribution is outlined, and a correlation with land and soil formations described. Five study areas were selected. Each had a distinctive pheasant population and land formation, and in total comprised about three-quarters of the primary pheasant range. Data were collected from extensive surveys made by sportsmen, farmers, biologists, rural mail carriers, and conservation officers. ii Roadside surveys by the mail carriers and conservation officers were most useful, and coaplemented each other. The approximately 500 car- riers who regularly cooperated provided good volume of data, but could be asked only infrequently to make surveys. The officers (about 55 in pheasant range) did not provide as large a volume of data, but could! be asked to record observations over long periods to determine the effect of phenology on surveys. Surveys were made during the four seasons. Data were recorded by county units, and examined by tabulations for study areas. Mag-firowing-cock counts, self-adjusting for phenology, were considered the most reliable for spring cock population estimates. Carriers' spring surveys of both pheasant density and sex ratio were sensitive to phenological differences. As the days progressed in mid- April, observed density increased. The carriers' counts were cor- related to crowing-cock counts, suggesting a method for adjusting counts for phenology. Sex ratios obtained from observations of harems may be more nearly true than those obtained from all observations. Munrood density indices increased as the sunner progressed from early June to mid-August, at a predictable rate, permitting adjustment for timing of brood counts. Sumner brood counts by carriers showed an excellent correlation with fall kill. Pram the former, kill could have been predicted with an average error of 4 per cent (greatest error 15 per cent) in an 11-year period. Brood sizes reported by carriers did not change significantly from year to year. iii {gly-September extensive roadside surveys during mid-day were valueless. Because of differential vulnerability of adults and young cocks to hunting, I was unable to determine true cock age ratios. Sex ratios reported by hunters were not valid. Hunter success data, discreetly used may yield valid indices to fall populations, but com- puted kill remains the best index. Multoadside observations of pheasants were correlated with snow depth. Regressions of cocks, hens, total birds and sex ratio noted by officers each day on daily average snow depths were plotted for two entire winters. The regression was apparently not linear; in addition the regression differed for cocks and hens, and hence sex ratios changed as snow depth increased. In no regressions did the Y-intercepts and the slopes show the same relationship. Interpre- tation of the data was hamered by a lack of a knowledge of the true population dealt with. Populations trends by study area from 1937 to 1956 were recon- structed and discussed. Areas of lake-bed soil origin showed similar patterns, although widely separated geographically. iv A POPULATION SURVEY OF THE RING-NECKED PHEASANT IN MICHIGAN By Ralph Austin MacMullan A THESIS Submitted to the School for Advanced Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Zoology 1960 PREFACE In 1946, faced by a pheasant depression, the Game Division of the Michigan Department of Conservation set up a research project to survey the ring-necked pheasant (Phasianus colchicus) population in Michigan. Its purpose was to determine what things affect pheasant numbersnboth in time and space. To do this it was also necessary to devise new can-- sue methods. This paper is a report on methods for estimating pheasant numbers and a reconstruction of past populations. The study is not from the traditional life-history standpoint, but rather from the population dynamics standpoint. Collection 93 115;; The bulkof the material for this report was collected while I was in charge of pheasant investigations for the Game Division from 1947 to 1950. This work was financed by Federal Aid in wildlife Restoration Project W-38-R. J. P. Linduska was the first leader of this project and conducted surveys in 1946 and early 1947. After 1950 the Game Division continued many of the surveys that I had set up and by prior agreement I have used the data from them when necessary. S_t_a_§_t_s_s_ g; _O_u_r_ Knowledge 9; Pheasant Biology it; .1_9_l_r§. Pheasants had been managed on the preserves in Europe for many hundreds of years. Details concerning their propagation had‘besn Swell, worked out and we knew many basic life history details. Leopold 35 5. ii (1943) had determined an average life span of wild pheasants from a population turnover study. Since pheasants are polygamus, a surplus of cocks could be hunted each fall with little prejudice to the next spring‘s breeding effort. Shick (1947) had found that in pens, one rooster could assure as good fertility in fifty hens as in three. Studies of the effects of hunting on pheasant populations indicated that hunting seasons restricted to cocks only could safely allow ex- tremely heavy hunting pressure. Shick (1952) on the Prairie Farm had demonstrated that 200 gun hours per acre during a 22-day season could remove as many as 90 per cent of the cocks, leaving a sex ratio of 10 hens per cock with no apparent damage to the next year's production. Certainly it was well proven that Michigan's hunting seasons on cocks only were not seriously affecting pheasant populations. Research workers had begun to work on census techniques. The habit of cocks of crowing repeatedly in early morning hours during the breed- ing season was being exploited to develop an index based on counting the number of crowings heard per unit of time. (McClure, 1945; Kimball, 1949) Roadside censuses were being tried with mixed successumostly poor. lhthods for aging pheasants as young of the year or older had been worked out (Linduska, 1943; 1945; Kimball, 1944). The Extensive m In 1946, when this project started, the pheasant had been estab- lished for only about 30 years in most of its American range. Although some research had been started in the 1930's (and interrupted by the war in the 1940's), to my knowledge no extensive study of state-wide populations had been undertaken. iii From the outset, it was decided that this study should be extensive, dealing with state- or area-wide pheasant populations rather than an in- tensive survey of populations on small areas. Most of the research on pheasants in North America had been in- tensive. Such studies had offered some clues to the population dynamics of pheasants. But when interpreted in terms of a state-wide pheasant population, intensive studies had been found wanting in two particulars: 1) Truly representative study areas are difficult to find. Data from studies in small areas are often inadequate or even mis- leading when interpreted in terms of the entire pheasant population of the region they are meant to represent. 2) Even in areas that may be representative, the small number of birds involved in intensive studies allows large magnification of error when conclusions are applied to a widespread population. The intensive worker is also uncertain about the effect his activities may have on the observed animals and the possibility that factors peculiar to his study area are not common to the rest of the pheasant range. An exanple of the inadequacies of intensive studies as indicators of state-wide populations is shown in Chapter 2; if one had used popu- lation figures from Rose Lake and the Prairie Farm (two quite tlmrough intensive studies in Michigan) as an index to population trends of pheasants in all of Michigan, he would have been misled. The most isportant shortcoming of intensive studies as indicators of large populations is sanple size; even though an intensive study pro- vided accurate information on a pheasant population, we would probably need many dozens of such studies to represent the state adequately. 'iv The extensive study is not meant to replace the intensive study, but rather to complement it and to answer more accurately questions too often improperly asked of the latter. Extensive studies may sometimes require intensive studies for interpretation and may point out the need for further investigation of certain life history phenomena. Extensive surveys also have inherent shortcomdngs. They are de- pendent upon data which are often not gathered critically. In some cases observers are untrained and in virtually all cases data are gathered casually, incidental to other duties and subject to the voluntary cooperation of the observers. Despite the fact they cover wide areas, care must be taken to assure adequate sanpls sin in ex- tensive surveys, too. Rsretofors, these shortcomings had discouraged the use of data gathered extensively. The "roadside survey" developed in Iowa (Bennett and Bhndrickson, 1938) and Pennsylvania (Randall and Bennett, 1939), in which trained observers drove selected routes on carefully selected dates and time of day, had been severely criticised and in some forms has been shown to be statistically inadequate (Fisher, Biatt and Berg- sen, 1947). notwithstanding these objections, the extensive survey was tried in'Michigan, and has become a useful tool. Today, extensive surveys have become the basis for setting pheasant hunting regulations each year, and are the Game Division's best source of information on pheas- ant populations from season to season. Acknowled nts I am indebted to the Game Division and particularly to Mr. H. D. Ruhl, Chief, for the opportunity to conduct this study, to V J. P. Linduska who designed and supervised the first extensive pheasant surveys on this project and to P. H. Dale and D. w. Douglass who served as my supervisors. R. I. Blouch and V. S. Jensen who followed me as leaders of this project continued a number of the surveys I had con- ducted, providing me with data over a longer span of years. I express my appreciation to L. L. Eberhardt for his help, advice and instruction in the statistical parts. To professors G. J. wallace, G. A. Petrides, and W. B. Drew, the ‘mmmbers of’mw graduate committee, I offer my sincere thanks for their patience and encouragement during the long drawn-out period this study has taken, and for their help in the preparation of this report. thy employees in the Conservation Department--biologists, of- ficers, aides, and others--have contributed in advice and untold thousands of hours of work collecting data. vi TABLE OF CONTENTS Page m FACE O O O O O O O 0 O O O O O 0 O 0 O O I O O O 0 O 0 0 O O 1 1 LIST OF Tums O O O O O O O O O O O O O O O O O O O O O O O O x LIST OF ILLUSTRATIONS O O O O O O O O O I O O O O O O O O O O O X11 Chapter 1. THE ESTABLISHMENT OF PHEASANTS IN MICHIGAN . . . . . . H l 1 First Releases (1895-1917) . . . . . . . . 1 2 The State's Release Program . . . . . . . 1.3 Growth of the Pheasant Population . . I 4 1 5 raa~e-ha The Genetic Origin of‘Hichigan' s Pheasants Establishment 0f Pheasants in Neighboring States 0 O O O O O O O O O O O O O O O O O 7. 0 l3 2. VALIDITY OF ANNUAL PHEASANT KILL COHPUTATIONS . . . . . 15 In t to due t ion 0 O O O O O O O O O O O O O O O O 15 Bird Hunters' Tally Cards . . . . . . . . . . . 15 x111 Reported on License Stubs . . . . . . . . . 18 The Compulsory Hunters' Report Card System . . . 20 Vin Coevering' s Free Press Pheasant Telly . . . 20 NNNNNNN NGUkUNI-I' wuyne County Sportsman' s Club Pheasant Tally. 24 Comparison Of Gemputed Kill with K111 on Sample Areas 0 O O O O O O O O O O O O O O O O O I O O 26 2.8 Studies of Bias Of Hunters' Report Cards" . . . 33 2.9 Computing K111 by Random.Sample Mail Survey . . 36 2.10 Computing K111 by County . . . . . . . . . . . . 36 Zell Conclusions . . . . . . . . . . . . . . . . . . 39 3. DISTRIBMION or mwms . O O O O O O O O O O O O O O 42 3 1 Introduction . . . . . . . . . . . . . . . . . . 42 3 2 General Distribution of Pheasants . . . . . . . 42 3 3 Correlation of Pheasant Distribution with Soils. 43 3.4 Definition of Pheasant Range . . . . . . . . . . . 48 3 5 Selection of Study Areas . . . . . . . . . . . . 48 3 6 Conclusions . . . . . . . . . . . . . . . . . . 51 vii Chapter 4. TABLE OF CONTENTS nnnwm or Ems m s 03an O O O O O O O O O 0 Int reduc t ion 0 O O O O O O O O O O O O O 0 Definition and Description of the "Extensive Surveys by Sportsmen . . . . . . . . . . Surveys by Rural Hhil Carriers . . Surveys by Conservation Officers. . Surveys by Farmer Cooperators ... . Ctofing'cock Sumyfl e s e e s e e e Surveys by Game Biologists . . . . . Summary and Conclusions . . . . . . . ##4##«Fk-F ## @OVO‘UI#U NH 8 PR m ’0’ muons O O O O O O I O O O O O O O O O 1 Introduction . . . . . . . . . . . . . . . 2 Growing-cock Surveys and Carriers' Surveys. 3SexRatios................ 4 Density . . . . . . . . . . . . . . . . . . 5 Conclusions . . . . . . . . . . . . . . . . MD PRODUCT I“ O O O O O O O O O O O O O O O I O 6 1 Introduction . . . . . 6 2 Brood Production . . . 6.3 Timing of Brood Surveys 6.4 Brood Size . . . . . . . . . 6.5 6.6 Percentage of Hens Without Broods . . . . . cone 1 u. ion! 0 O O O O O O O O O O 0 I O 0 O PREDICTION OF I‘LL KILL PROM SUMMER BROOD COUNTS . sumyn O O O O O O O O O O O O O O O 0 O O 7.1 Introduction . . . . . . . . . . . . . . . . 7.2 Correlation of Carriers' Brood Counts with Computed Kill . . . . . . . . . . . . . . 7.3 Source of Error in Correlation of Brood Density with Computed K111 . . . . . . . . rmumTIM'Lzeeseseeeeeeeeeee ' O 1 Int raduc t ion 0 O O O O O I O O O O O 0 O 0 O 8.2 Preseason Sex Ratio Surveys . . . . . . . . 8.3 Age Ratios in the Phll Kill . . . . . . . . 8.4 Hunter Success as a Population lisasuremsnt. 8.5 Hunter Opinion Polls . . . . . . . . . . . 8.6 Conclusions . . . . . . . . . . . . . . . . viii O O O O O Page 53 53 53 56 56 62 as 66 . 67 as 70 7O 71 74 79 85 87 87 88 90 92 98 99 100 100 100 107 115 115 115 121 122 123 124 TABLE OP CONTENTS Chapter 9. WINTER POPULATIONS . . . . . . . . . . . 9 1 Introduction . . . . . . . . 2 Carriers' Postseason Surveys 3 Officers' Winter Surveys. . . 4 Conclusions . . . . . . . . . 10. POPULATION TRENDS-nvANNUAL AND LONG TENN 10.1 Introduction . . . . . . . . . . . . 10.2 Reliable Indices to True Populations 10.3 Sex Ratios . . . . . . . . . . . . . 10.4 Meshing Seasonal Populations . . . . 10.5 Population Trends by Study Areas SW C O O O O C C O O C C O O O C O O O O . mu 0 O C O O O O O O C O O C O O O C C O C B IBL 1mm 0 O O O O O O O O O O O O O O O O 0 ix 0 O O O Page 126 126 126 129 142 144 144 146 146 149 151 156 162 166 Table 2 .1 2.2 2.3 2.4 205 2.6 2.7 2.8 3.1 3.2 4.1 5.1 5.2 5.3 5.4 LIST OP TABLES Pheasant Hunting Data from Bird Hunters' Tally C‘rd.,1929-1935eeeeeseeeeeeeesee Pheasant Kill Coquted from License Stubs, 1932-19350eeeeeeeeeeeeeeeeeee Van Coevering's Free Press Pheasant Tallies, 1931-1956eeeeeeeeeeeeeeeeeeee Wayne County Sportsman's Club Pheasant Tallies, 1947-1949 O O O O O O O O O O O O O O O O O O O O Frequency Distribution of Hunters According to Huber of Cocks Shot, as Reported to HCSC and st.t.’ 1949 O O O O O O O O O O O O O O O O O O O Coqarison of Cocks Shot per Hunter, HCSC and St.t.’ 1947-1949 e e e e e e e e e e e e e e e e e Coqarison of Actual 1937-1949 Kill on Two Saqle Areas with coquted Kill in Containing Counties . Coqarison of Coquted Kill as Determined from First 20,000 Returns with Final Returns . . . . . Statistics Concerning Study Areas . . . . . . . . Per Cent Pirst- and Second-class Land in Study Ar.“ O O O O O O O O O O O O O O O O O O O O O O Average Lengths of Carrier's Routes . . . . . . . St-ary of Growing-cock Surveys . . . . . . . . . Sun-nary of Carriers' Spring Surveys . . . . . . . Sex Ratios Observed by Carriers in Spring Surveys. Frequency Distributions of Harem Sizes 'as Reported by C‘rrier. O O O O O O O O O O O O O O’ O O O ‘O O Page 17 19 22 27 28 29 31 35 50 52 61 73 75 76 77 Table 5.5 506 6.1 7.1 7.2 7.3 704 8.1 8.2 9.1 9.2 9.3 LIST OF TABLES Adjustment of Carriers' Density Indices to Common St‘rtm D‘te O O O O ' O O O O O O O O O O O O - .. O Daily Pheasant Observations by Carriers, Spring, 1950 O O O O O O O O O O O O O O O O O O O O O O Size of Broods Reported by Carriers . . . . . . . values of Correlation Coefficients (r) for 16 Comparisons of Computed Kill with Carriers' Brood Den. it, Ind tea. O O O O O O O O O O O O O O O O O Regression of Computed Kill on Logarithm.of Carriers' Brood Density Indices . . . . . . . . . Error in Prediction of Computed Kill from Carriers' Brood Density Indices . . . . . . . . . Correlations of Brood Size and Two Pepulation m1c.‘ O O O O O O O O O O O O O O O O O O O O O Observed Sex Ratios on Opening Days . . . . . . . Pall Pheasant Observations by Officers . . . . . Officers' Lste'Winter Survey - 1946 . . . . . . . Summary of Carriers' Postseason Surveys . . . . . Officers' Pheasant Counts on Days with a Trace o r no snow O O O O O O O O O O O O O O O O O O O xi Page 81 83 96 101 105 108 113 118 119 127 128 135 Figure 1 . 1 1.2 2.1 2.2 2.3 2.4 2.5 3.1 3.2 3.3 4.1 4.24 4.3 5.1 5.2 5.3 6.1 6.2 LIST OP III-DSTIATIONS Hap, Areas Considered Good Pheasant Ranting in 1930 . . Hap, Hhere Pheasants Here Considered Abundant in 1934 . Pheasant Kill Computed from hell G-e, lhnters' Report Cards, 1937-1956 . . . . . . . . . . . . . . . . Computed Kill Compared to Van Coevering's Tally . . . . Regression of Computed Kill on Pheasants Seen per Hour in Van Coevering's Tally . . . . . . . . . . . . . Hap, Graphs of Computed Kill by County . . . . . . . . Indices to Fall Populations. 1932-1956 . . . . . . . . Hep, Computed Kill per Square Mile by County . . . . . Hap, Groups of Soil Associations in Southern Hichigan “a Study “a“ O O ,O O O O -O O O O O D O O O O O O O O Hap, Administrative Delineation of Pheasant Range . . . Pheasant-aging Cards Sent to Sportsmen . .. . . . . . . Hap, Location of Carriers' Routes . .7 . . . . . . . . . Hap, Officers' Administrative Districts . . . . . . . . Hap, Location of Growing-cock Survey Routes . . . . . . Frequency Distributions of Harem Sixes as Reported by C‘rrier. O O O O O O O O O O O O O O O O O O O O O O Relationship of Craving-cock Index to Carriers' Spring Density Index, Adjusted to Canon Starting Date . . . . Brood Density Indices as Reported by Carriers and Officer., 19“ O O O O O O O O O O O O O O O O O O O O Officers' Brood Density Indices . . . . . . . . . . . . xii 10 21 23 25 37 40 46 49 57 60 72 78 82 89 91 Figure 6 . 3 6.4 7.1 702 7.3 90l 9.2 9.3 9.4 9.5 9.6 9.7 10.1. 1002 LIST OP ILLUSTRATIONS Carriers' Daily Brood Counts Compared with Precipi- t‘tim O O O O O O O O O O O O O O O O O O O O O O O Frequency Distributions of Sizes of Half—grown Broods Observed by Carriers . . . . . . . . . . .‘ . . Regression of Computed Kill on Carriers' Brood Density Indices for Study Areas, 1946-1949 . . . . . Regression of Computed Kill on Logarithm of Carriers' Brood Density Index for Primary Pheasant Range, 1946- 1956 O O O O O O O O O O O O O O O O O O O O O O O O Comparison of Computed Kill with Logaritl- of Carriers' Brood Density Index for Study Areas, 1946- 1956 O O O O O O O O O O O O O O O O O O O O O O O O Comparison of Daily Average Snow Depth with Daily Pheasant Observations by Officers . . . . . . . . . . Regression of Pheasants Observed per Officer-day mnOily AVOI’O‘O 8n" 389th e e 'e ‘e e e e e e e e s e Regression of Cocks Observed per Officer-day on DailyAverage SnowDepth . ... . . . . . . . . . . . Regression of Hens Observed per Officer-day on DailyAverage SnowDepth . . . . . . . . . . . . . . Hodel Suggesting a Relationship of Observability of a Pheasant Population to Snow Depth . . . . . . . . . Model Suggesting Shift in Relative Observability of Cocks and Hens as Snow Depth Increases . . . . . . Increase in Sex Ratio as Snow Depth Increases . . . . Schematic Diagrms of Census Information Needed . . . Computed K111 in Study Areas, 1937-1958 . . . . . . . xiii 93 97 102 104 106 131 133 136 137 138 139 141 145 152 Chapter 1 THE ESTABLISHMENT OF PNEASANTS IN MICHIGAN 1.1 gig; 11616.ne- gags-fig) On‘Harch 27, 1895, Hr. Arthur G. Baumgartel liberated sev- eral pairs of ring-necked pheasants on the Henry Harrington Farm at Harlem, in Ottawa County. This was the first recorded release in Michigan.1 A brood was observed in the vicinity on August 24, 1895. This release was not hastily conceived. For some years Baumgartel had considered the need for a new game bird. He and his friends had weighed the relative meritsiof pheasants and Hungarian partridge as suitable birds for Hichigan. In 1893 he consulted with Emerson Hough, western representative of "Forest and Stream” and they decided that the Mongolian Pheasant was the best bet. He had tried to obtain wdld birds from Oregon where they had already become established, but that State had already forbidden exportation of pheasants. So he purchased two pairs of pheasants from a private game farm.in New Jersey in August, 1893. That year the‘Hichigan Legislature passed a law protecting pheas- 1This event is rather uniquely commemorated by a granite memorial on the Harrington Farm to the side of 08-31, six miles north of Holland. On it is etched the outline of a cock pheasant, and this inscription: "'rms BOULDER comments run near / PLANTING 0F PHEASANTS IN‘HICHIGAN. / THEY WERE RELEASED NEAR THIS 3201‘ / BY A. s. smnmL I or mLLAND, MICHIGAN, MARCH 27, 1895. / ERECTED BY I HOLLAND FISH AND CANE CLUB / HOLLAND POINTER AND BETTER CLUB I NOVEMBER, 1940." 1 ants for 5 years. In 1894 Bsumgartel organized the Holland Rod and Gun Club ma the club posted a $5.00 reward for "information leading to the arrest and conviction of anyone shooting the pheasants." In the fall of 1895 more birds were liberated. No known broods resulted from these releases, and it can be assumed that the birds disappeared shortly thereafter. Wilson (1948) has described this first attempt to establish pheasants in Michigan and reports a number of other newsptper accounts of releases by private persons in the early 1900's. He concluded that stocking attempts were numerous with " . .4. little more than a fraction of them succeeding." Dy "succeeding? Wilson probably meant breeding in the wild, for there is no evi- dence that any of these releases resulted in a permanent colony of pheasants, although quite probably some released birds did breed. A search of the records of State organizations responsible for game matters shows no reference to pheasants prior to 1913. In 1914 the Game, Fish, and Forest Fire Department of the Public Domain Commission issued its first biennial report, which listed permits to keep game animals. In that 1913-14 biennial report, 2 of 158 permits were for pheasants. In 1915-16, 6 of 349 permits were for pheasants, most for one or two pairs. There was no official magazine reporting on Conservation affairs inAHichigan before 1922,‘ but from 1913 to 1922 the "Michi- gan Sportsman," a commercial magazine, did a serviceable job of reporting on game matters. There are no references to pheasants in the incomplete volumes of this magazine available in Michigan libraries for the years 1913 through 1915. In the 1916 volume, however, the sponsors of the magazine were carrying on a vigorous campaign urging the State to establish a game farm for pheasants. Their campaign was thorough, their arguments many and optimistic. One of their most persuasive points was that New'York State had only recently acquired a game farm and had succeeded in establish- ing thriving colonies of pheasants. It is significant that in their arguments as to why the pheasant should be able to adapt itself here, not one reference is made to a colony already estab- lished in Michigan. If there had been successful colonies, how- ever small, it seems likely they would have been mentioned. Perhaps the most revealing official statement on the status of pheasants before the State's release program in 1918 is one by D. R. Jones, Chief Deputy, Department of Conservation, in a letter to Baumgartel dated December 17, 1926: "Personally, we have no data other than that submitted by you as to the early introduction of these fine birds in the State. However, we do know that H. B. Hershon and some of his associates secured and liberated somewhere between twenty-five and fifty birds in the Saginaw valley country during the 90's, and apparently the planting was not successful, as no hunter or observer, so far as we know, ever reported seeing birds in the locality up until some time after distributions were being made from the State Game Farm . . . "There was also a small liberation of ring-necks made by public spirited sportsmen of Clarkston, Oakland County, about 1905 or 6 and it is reported that a few of these birds survived and hung on up to the time distribution was started from the State Game Farm . . . "Along about 1911 or 12 some hunter from Gladwin County, I think, sent in feathers found in the woods that were classified as English or Chinese ring-neck . . . 1.2 1.3 He concludes by saying: "It is safe to say that not one hunter in one thousand ever saw a ring-necked pheasant until after the distribution of the birds from the State Game Farm was started in 1917." Thus, if there were any colonies of pheasants established in Michigan prior to 1918, they must have been very small and restricted. The State's Release Program The State purchased its present game farm at Mason in the fall of 1916. About 200 birds were purchased in the spring of 1917 and a stock of breeders was raised, but no birds were released. After a successful breeding season on the farm in 1918, 2,396 birds were released in the fall. Several thousand birds were released each year thereafter. Part of the release program begun in 1918 was distributing eggs (and some day-old chicks) to cooperating farmers and Sportsmen to hatch, raise, and release. While only a small percentage of these eggs resulted in birds released, such releases undoubtedly contributed to the stock, too. Pheasant releases were greatly reduced after 1951 and terminated in 1958. Growth of the Pheasant Population From 1918 through 1953, an average of about 24,000 eggs and chicks were distributed to cooperators and in addition an average of 6,700 grown pheasants were released by the State each fall (McCabe,.g§‘§l., 1956). Unfortunately, I can find no record of pheasant releases by county prior to about 1930. We know that most of the birds were released in the southern third of the state, but some were also released in the northern two-thirds. The pheasants released in 1918 and 1919 must have done remarkably well. These birds, plus the second-generation progeny of the 1918 releases, produced a population in the fall of 1920 which prompted this rather remarkable observation in the preface of the 1919-20 biennial report (gp. git.) quoting opinions expressed by " . . . sportsmen who have gone afield during the open season, 1920." " . . . the introduction of the ringrnecked pheasant to Michigan covert has proven successful to a degree exceed- ing expectations; . . . the experimental stage has been passed and the.species established as a permanent game bird in the State.” In 1923 the Department of Conservation recommended a state- 'wide season on pheasants (November 1-2 and 14-15) with bag limits of 2 per day, 4 in possession and 8 for the season. The legis- lature did not see fit to implement this recommendation. but the implication is obvious--after five years, in which perhaps 45,000 birds were released, pheasants were well enough established that game administrators recommended an Open season. In 1925 the season was opened in the entire state for 7 days October 25 to October 31, inclusive. There has been an open sea- son each year since then.1 The biennial reports from 1916 to 1930 contain much discus- sion and speculation concerning the establishment of pheasants in Michigan. In view of what we now'know'about the distribution of pheasants, these earlyuppinions are interesting and pertinent. 1Leopold (1931) reports there was a 45-day open season on pheasants in 1910. I can find no basis for the statement in ‘Hichigan records, and conclude it is in error--possibly due to an erroneous report which confused the meaning of the words ”par- tridge" and "pheasant." The season on ruffed grouse ("partridge") was open for 45 days in 1910. Undoubtedly they represent many different viewpoints; they are subjective, and they may even occasionally reflect the unfounded optimism of politicians. But despite the absence of statistical support, they are often astute and even prophetic. Following is a chronological paraphrasing of statements in these biennials. 1917-18 John Baird, State Game, Pish,and Forest Fire Commissioner, stated that already the release of pheasants "appears to have solved the small game proposition for the lower counties of Michi- gan." He felt it was doubtful that pheasants would do as well “north of the Saginaw Valley" but intended, nevertheless, "to make every effort to distribute the pheasant throughout the entire area of the state." 1919-20 " . . . we have passed the experimental stage in the matter of establishment of ringnecked pheasants in Michigan,. . ." a remarkable statement to make after three years of releases. "The prime purpose of the Department in bringing the bird to Michigan was to provide a substitute for the native ruffed grouse, now'almost exterminated in the depleted cover of the southern counties with their improved and sparsely wooded farming areas." Farmers reported that pheasants were breeding prolifically in all cleared land of southern Michigan. For the second time it was mentioned that pheasants were not expected to thrive in northern coverts, although administrators thought at the time that they were doing surprisingly well in the north. Expressions of doubt as to the suitability of pheasants for the north were based on fear of excessive predation as well as unsuitability of the range. 1921-221 Although there still seemed to be some argument as to whether or not the pheasant was a "budder," observations indicated it was not, and hence the bird would be restricted to the southern third of the state where snow depths were not excessive. 1927-28 By 1929 it was concluded that pheasants were firmly estab- lished, that about 30 of the southernmost counties could be con- sidered pheasant range, and that the game farm had fulfilled its ‘main purpose of supplying ” . . . breeding stocks which, when released, proceed to 'go wild,‘ increase of their own accord, and so continue to make and maintain satisfactory hunting." Since repeated plantings in the north had failed, it was thought that further plantings would be useless unless the local people fed the birds in the winter. There was some doubt that even such care would maintain birds, but a large scale experi- ment in‘Hanistee County was under way to see if such a system would work. Deparmment officials speculated that there might be about 100,000 pheasants in‘uichigsn in 1928. This estimate was based on a pheasant range of 30 counties, or about 20,000 square miles, and the assumption that there must be at least 5 birds per square mile in this range. 1Biennial report of the Deparmment of Conservation, which was created in 1921. By 1930 pheasants were apparently still expanding. In the fall of 1930, the State Conservation Department made the first official statewwide survey of pheasants. Conservation Officers throughout the state were asked to appraise their districts as "pheasant territory" using the terms "excellent, good, fair, poor, and hopeless." The map shown in Figure 1.1 shows the areas that administrators considered "good hunting." This conclusion is ‘made in the 1929930 biennial report: "A rather rolling country with tangled swales, unpastured wood lots, and brushy fence rows alternating with grain, clover and uncultivated fields, and where some ground is bare during most of the winter seems most favorable. "In most level areas, or where most of the land is cleared or farmed intensively, or in areas containing high percent- ages of wild woods or in deep snow districts, the pheas- ant seems to succeed poorly, if at all." Despite the fact that this conclusion was based on uncriti- cal opinions of a large number of non—professional observers spread over the entire state, usually with only one observer per area, the conclusion they reached was probably sound. It is quite likely more than coincidence that observers from the flat, heavy clay soils of lake-bed origin bordering the Great Lakes in south- eastern Michigan should rather consistently report that country as poor pheasant range. That same lake-bed soil in southeastern ‘Michigan later became the best pheasant range in Michigan and among the best in.North.America. In 1934 officers were again asked to appraise their districts, this time with terms "abundant, scarce, or suitable for pheasants but none reported." Figure 1.2 shows the areas in which the offi- cers said pheasants were abundant. These areas are roughly twice A... J “m -'~4 1.: L Fig. l.1--Areas considered good pheasant hunting in 1930. . in: | I! wratsdsjw l ...,__. 4.. , e v-‘ '0 . f‘.‘h-~-° -- e ‘ ,9... H . ' C 0'. o l "f ‘ " “airmail . . gimm;9 ' "°’“fi “‘ L --- --u‘-.s-mo-- an-..” b.- o Fig. l.2--Hhere pheasants were considered abundant in 1934. 10 1.4 11 the acreage classed as good hunting in 1930, although the 1934 classifi- cation is certainly more restrictive. This would indicate that pheas- ants had increased substantially from 1930 to 1934, and the lake-bed clay areas in southeastern Michigan apparently were beginning to produce many more pheasants. The original records from which these maps were prepared have been destroyed, but the 1930 map is referred to in the 1929-30 biennial, in which it is stated rather conclusively that "It has become evident . . . that north of town line 20 little, if any, of the territory has proven capable of main- taining even fair hunting except locally and as a result of repeated and heavy plantings." In spite of the fact that pheasant pOpulations were still building up in the early 1930's, these two maps of pheasant distributions show quite clearly that pheasants had about spread to the limits of their range by that time. There are no large areas inhabited by pheasants today that were not colonized in 1930. The Genetic Origin_gf Michigan's Pheasants Michigan's pheasants are a mixture of a number of subspecies of the genus Phasianus. Examination of the plumage of cock pheasants picked at random from Michigan's pheasant range would show this mixed ancestry; rarely would one find a pheasant typical of any one subspecies. Taxonomists and historians are not completely agreed on the deri- vation and taxonomic status of the species and subspecies of Phasianus. Introductions of several subspecies, freely interbreeding where their ranges overlap, from several widespread areas in Asia, and long confinement and artificial mixing and selection in game farms have thoroughly confused the genetic composition of the game farm birds, from which our wild birds come. 12 Delacour (1951) describes the pheasants brought into Europe and America as follows: Phasianus colchicus torquatus is one of a group of 17 sub- species in eastern Asia. This subspecies (and presumably others closely allied) was the stock from which perhaps most of the introductions to England in the 18th century and America in the 19th century were made. The so-called Mongolian Pheasant he describes as _l_’_._ _<_:_._ 20.3- golicus, typical of the Kirghiz pheasants, a group of three sub- species in western Asia, far removed from Mongolia. They are not linked to the eastern Asia groups. He reports that Hasenbeck introduced some of these birds to England in 1900, and that from these the game fanm stocks (in America as well as England) of Mongolian Pheasants were developed. The game breeders' English blackeneck pheasants are pre- sumably the result of introductions of‘gé'g; colchicus, (or one of the other two subspecies in this group of Caucasian pheasants) from the western edge of Asia. Taxonomists agree that.g; versicolor. the green pheasant, restricted to the islands of Japan, stands the test of a separate species. The melanistic mutant Qg;.g; mut. tenebrosus) was developed in English game fanms about 1880.. It breeds true, with no inter- mediate forms, and appears to be exceptionally hardy. Michigan pheasants most nearly resemble torggatus; com- monly, cocks show coloration indicating mongolicus ancestry. Rarely one sees a bird that shows characteristics of versicolor. 1.5 13 Occasionally a cock is lacking the white neck ring. This may or may not reflect colchicus influence, since the white neck ring is a variable characteristic, and certain individuals of the 17 subspecies in the torggatus group of eastern Asia‘may lack it. ‘The Game Division receives perhaps a half a dozen reports each year of observations of white, or partially white pheasants. Some of these may be the result of albinism or natural mutation, but I feel that some may result from private releases or escapes from private holdings of the game breeders' fancy white pheasant. There are some melanistic mutants in a small colony of pheas- ants around Eose City, in Ogemaw County. They are descendants of a private release in the middle 1930's. While these mutants are not common, the strain maintained itself at least 15 years, until the early 1950“s, when the Game Division released a few dozen more game farm melanistic mutants in that area. Hunt (1956) recalls that at the Mason State Game Perm in the spring of 1918 “ . . . breeding stock of about 500 females (pre- sumably Chinese ring-neck stock] . . . were mated to some very fine purebred Mongolian males." The releases starting in the fall of 1918 were undoubtedly successful, so we can assume Michi- gan's pheasants were strongly influenced by Mongolian stock from the first. Establish-ant _o_f Pheasants in Neighboring _S_t_a_t_:2§ Pheasants apparently becane well established in all of the Lake States (Wisconsin to Ohio) at about the same time. As in Michigan, private releases were made around the turn of the cen- tury, with but few succeeding. Indiana, Ohio, and Michigan were 14 operating State release programs in the second decade of the cen- tury. Illinois and Wisconsin began serious release programs in 1928 and 1929, respectively, but other private releases had already established the birds in some areas. Leopold (1931) pre- pared a map showing the distributions of pheasants in the Lake States in 1928-29. From the map we can say that in general pheasants had: 1) become established and completed their major expansion 1 in Ohio, Indiana, and Illinois, 2) reached the limits of their range but were still increas- ing in Michigan, 3) still some potential range in Wisconsin in which to spread. we can also conclude that the establishment of pheasants in each of the Lake States was essentially independent of pheasant populations in adjoining states. Probably by 1940 pheasants had become established in all the Lake States range suitable to them. It is unlikely that any sizable new area will be colonized by the brand of pheasants we now have. 2.1 2.2 Chapter 2 VALIDITY OF ANNUAL PHEASANT KILL COMPUTATIONS Introduction When this study was begun in 1946, kill figures computed from. small game hunters' compulsory reports were the only statistics that showed any promise as a reliable source of information on state-wide populations for the preceding years. This system.had been in effect since 1937, and provided what appeared to be rea- sonable estimates of each fall's kill. There were, however, no other data on state-wide populations with which to evaluate this computed kill. There were a number of other surveys of doubtful value. One of the first objectives of the project, then, was to try to evaluate this computed kill as a measure of fall popu- lations, and to investigate the possible usefulness of other kill surveys that had been made. In the following sections, the computed kill figures and various other hunting season surveys are discussed, more or less in chronological order. §i5§.8unters'_gallz Cards In 1929, the Department started its first system for obtain- ing specific data on pheasant hunting in Muchigan. Department workers distributed "Bird Hunters' Tally Cards" to hunters, who re- corded such information as the hours and days they hunted, and the 15 16 number of birds they saw and the number they shot. These cards were returned to the Department and tabulated. Tabulations from these tallies for the years 1929 through 1935 are summarised in Table 2.1. At best, only a few hundred tally cards were returned to the Department, so the sample is extremely small. Nevertheless, the reporters may have been a rather consistent group whose reports could reasonably be compared from year to year. Probably the best measure of pheasant populations from these tally cards is in terms of success indices (birds flushed or shot per gun hour). Any extension of kill per gun hour to total kill through calculations involving numbers of hunters seems impractical. In recent years (1937-1959) a 10 per cent change in numbers of licenses sold from one year to another has been unusual. But license sales during 1929-1935 fluctuated radically--a 55 per cent increase in 1933, and a 32 per cent decrease in 1931! There may well have been complicating factors not known to us today which were responsible for these fluctuations. For example, in 1931 the Department changed vendors from county clerks to Department- selected private dealers. Whatever the reasons for these changes in license sales, suspicion of their validity as a source of data on numbers g§_hunters precludes their use as a factor in esti- mation of total kill. If this appraisal is of any value, we might interpret the period of 1930-1935 as one in which pheasants were increasing, with the suggestion of a slight slump in 1935. In 1935, the last year of this survey, publication of the tally card in newspapers did not result in a much larger return, so the system was abandoned. l7 .oanuu «any as oouoouuoo noon obs: use .Hmwmooqm ago on uoouuoooa one: one mauoouuooow ooueasoaeo one: awash «Boo you some a «mn.nmn Ha. «s. enn.os ooe.s nan.ss . hon.“ . new e me “man moo.o¢m «n.~ ma. oma.o~ nmo.~ ano.- on¢.~ flaw, a NH «mad aea.~mn . oo.~ as. nnn.m «we «we.» mem.s asu a NH «mas m~m.¢- no.~ ma. a Na «nag coo.e¢~ e nH.H me. e «a Haas oau.~nn am. am. Hum.~ one nma.~ moo «we a n onoa dom.o¢n ma. e n mums modem «3979.6 39755 oases E oommem :3: when euwomum awe—.3 condom user sundown \osemsym use HHHM mouan mxooo uooo fuouosm mo .oz mum ow when ocean. , condom nnmanauaa Hmnm .asao anodes: anemones: unusuaoov HHH seamen as gene €333: Efiuaoe .HHH cosmos an ensues: on on vengeance one: sauna mo Asumv oo~.odn . 5.18 339.50 “Sm a n .0862 mo mouse undue: :ooueaaueo: no ouuomu 30.335930 g on. CHE—HOD an a» EH00 n H coco.oeo nna».nes an. seenn.nmn to.a cos.~ oo~.H named usages: «oe.ok~ «mm aoo.o¢n e~.~ ~nm.~n~ aea.~as «mam ~ooe.oea. osn.een «an wen.oa~ mn.~ mne.aae new.ac Name any Ase Amy Amy Ace AmV . any AHV «any «as as been seesaw madam meanness“ subdue «unease Haas doe: 33.3% o memos; ammo pom sense...“ nouns: use museums—3 . among: uo use» :3 38. Edison So. no .02 mo .02 nnaH-~naH 83m awZMOHA to: nun—buxoo EM gamma N.N "55—. 20 2.4 The Compulsory Hunters' Report Card System 2.5 Starting in 1937, each hunter was required by law to report the game he took each year to the Department of Conservation, on an addressed card furnished with the license. These report cards re- mained essentially unchanged from 1937 until the system was discon- tinued in 1956. The annual pheasant kill for the state, as computed from these small game report cards, is compared with license sales for the years 1937 through 1956 in Figure 2.1. These kill figures will be referred to as the "computed kill" in the rest of this report. The method of computing this figure is shown in the appendix. lag Coevering's Free Press Pheasant E11 Jack Van Coevering, Outdoor Editor of the Detroit Free Press, has conducted a "pheasant tally" each year since 1931. Shortly after the pheasant season each year he requests hunters to fill out a form which he publishes in the Free Press. as usually receives about 2,000 replies, and it is reasonable to assume they represent a fair sample of pheasant hunter performance, although the sample is undoubtedly biased according to distribution of the paper's circulation in the state, and by the type of hunter inter- ested enough to submit a tally. Results of his tally are shown in Table 2.3 I compared Van Coevering's surveys with the State's computed kill for the 13-year period from 1937 to 1949 inclusive. This comparison is shown graphically in Figure 2.2. In this figure, the two graphs are equated arbitrarily at 1937, since units for the two lines are not directly comparable. The correlation- 21 63.733 .233 muons... .3355 sin :23 Sum eon—Ease 3.3 umeneonmuuud .9: .3238: 2: cab 09. vmh vmh N50 navuo name oN.0 #00 3‘0 N00 can 3% N3 5%“... 9&0 Sun syn 03 8Ymu4u>¢:m 0:3 50... :05 § 9 embossed 34...: mpzamauxa 8:333 . .. 08.83 .moe3 .anue .9323: :05. eukaaxoodmj... mpzamaura ouhaxfimu ._ 80.80.. 22 TABLE 2.3 vm oosvsamc's ms puss PHEASANT TALLIBSI 1931-1956 ' Pheasants SeenAper Hour Number of Year Sex Ratio Counties Hens Cocks Total (Hens/Cock) Involvadz 1931 - - 2.4 12 1932 1.5 0.8 2.3 2.0 27 .1933 1.7 0.9 2.7 2.0 23 1934 2.4 0.7 2.1 3.4 31 1935 1.3 0.8 2.1 1.6 30 1936 1.5 0.8 2.3 2.0 27 1937 1.5 0.9 2.4 1.7 34 1938 1.8 1.1 2.9 1.6 34 1939 1.7 0.9 2.6 1.9 44 1940 1.9 0.9 2.8 2.0 31 1941 3.1 1.6 4.7 1.9 27 1942 2.8 1.4 4.2 2.0 26 1943 4.3 2.0 6.3 2.2 19 1944 3.6 1.3 4.9 2.8 29 1945 1.9 0.8 2.7 2.4 2Q 1946 1.4 0.6 2.0 2.3 35 1947 1.1 0.6 1.7 1.8 34 1948 1.0 0.6 1.6 1.8 37 1949 1.5 0.7 2.2 2.1 32 1950 1.3 0.7 2.0 1.8 - 1951 1.8 1.0 2.8 1.8 - 1952 2.1 1.0 3.1 2.1 - 1953 2.1 1.2 3.3 1.8 - 1954 2.7 1.0 3.7 2.7 - 1955 2.6 1.2 3.8 2.2 - 1956 1.6 0.9 2.6 1.8 - 1 pan from Van Coevering (1949; 1950;1957). 2 Data not available 1950-1956. However, 34, 36, and 30 counties were involved in tallies made in 1957, 1958, and 1959 respectively. Number of hunters‘ reports has been between 1,900 and 2,500 most years. Computed Kill -(Stote) 2,000,000 a F ’I \ I \\ ”‘v’ \ I,ooo,ooo - — COMPUTED KILL ’ State soo,ooo- --- BIRDS SEEN PER HR. Von Coeverinq l l I l l J 1 l l l 1 I937 '39 '4I '43 '45 '47 '49 Fig. 2.2--Ccnputed kill compared to Van Coevering's tally. 23 Birds Seen Per Hr.-(Von Coeverinq) 2.6 24 coefficient of birds seen per hour by hunters reporting to Van Coevering-ea the computed kill for the 20-year period 1937 to 1956, inclusive, as shown in Figure 2.3, was calculated at r x .876. This is a good correlation. Whatever the differences between the two, it seems significant that the trends shown are similar, and that after 13 years the lines did not diverge appreciably. The greatest concern for the reliability of the computed kill had been that as the report card returns dropped, the dwindling sample might represent an increasing proportion of more successful hunters. Such a bias would progressively inflate the computed kill. Since Van Coevering's number of reporters has stayed remarkably constant, we can say, with reasonable confidence, that this inflation has not resulted, unless some unknown bias has affected the two relatively independent surveys in the same way. Waype County Sportsman's glub Pheasant Tally In 1947, Victor Beresford, Secretary-Editor of the Wazge Qggptz,§pg;5ggggjg_glgp_(the "WCSC") in Detroit, sent a form to some 7,000 members with the request that each member answer ques- tions concerning his pheasant hunting during 1947, and the 1946 season as well. Returns were sent to the Game Division and tabu- lated on IBM machines. The results were compared with the State's pheasant kill computation. The 1946 data were disregarded because of the long interim between hunting and questioning. Data ob- tained from these tallies appeared to have merit, and so I de- signed a form.asking for considerably more detail for the WCSC for 1948 and 1949. This form was designed particularly to collect 25 1400 '- 1200 — y e 462 + 175:: 1000 800 600 Computed K111 inIhousands (y) 400 I— 200‘ .— 4 I I I I I J_ 1 2 3 4 5 6 7 Pheasants 'Seen per Hour (2:) (Free Press Telly) Pig. 2.3-~Regression of computed kill on pheasants seen per hour in Van Coevering's tally. 2.7 26 data which could be cowared to the computed kill. In addition, I asked for hours hunted and pheasants killed each day of the sea- son, which the Game Division didn't get on the hunter report cards. Table 2.4 summarizes the data obtained from these WCSC pheasant tal- lies for 1947-4849. It would be difficult to calculate any index to total kill for the State from these tallies. A success index fromwcsc members, however, can be compared to a success index obtained from the Game Division's report cards. This is done in Table 2.5. the that this comarison is made only with hunters who reported shooting on; g; 93 birds, since unsuccessful hunters are not directly constable. (The State's report card does not specifically ask the hunter whether he hunted pheasants or not, and the “080 form does.) Another cowarison of success indices is shown in Table 2.6. Using the formula shown in the table, apparently the State success ratio could be predicted accurately on the basis of the WCSC saqle. Comparison 9_f_ Muted K113]; with _K_i_l_l_ 93; m 53.32 0 Both Van Coevering's tallies and the W086 tallies show good correlation with portions of the State data. Since both eagles are independent of the State sample, they serve as a measure of proof of. the value of the State figures, even though the two former are undoubtedly subject to bias because both groups are heavily represented by the metropolitan Detroit area (e.g., more than half the WCSC sample hunted in the counties surrounding Detroit in 1949). However good these correlations may be, they do not offer any information as to how real the figures are. All three tallies were 27 TABLE 2.4 WAYNE COUNTY SPORTSMAN'S CLUB PHEASANT TALLIES 1947-1949 1947 1948 1949 no. tallies returned 434 738 545 No. who bought small game licenses1 586 No. who reported hunting pheasants2 .321 502 469 cocks shot per pheasant hunter 1.69 1.65 2.09 Hburs hunted for the entire season 17.6 15.3 15.6 Sex ratio of birds flushed 1:2.5 1:2.3 1:2.7 Birds flushed per hour 1.2 1.1 1.4 figure to kill each Cock 10.4 9.2 7.4 1N6t asked in 1947 zThis question was specifically asked in 1948 and 1949, and was not asked specifically in 1947 TABLE 2.5 FREQUENCY DISTRIBUTION OF HUNTERS ACCORDING 1'0 NW! 0? COCKS SHOT, AS REPORTED TO HCSC AND STATE, 1949 Number Per cent Hunters of Cocks Shooting 1, 2, 3, etc. Shot Per Cocks “mt“ State wcsc 1 ' 34 35 2 26 23 3 13 10 4 12 13 5 5 7 6 6 7 7 1 2 81 3 3 Total 100 100 1 Season limit 29 TABLE 2.6 COMPARISON OF COCKS SHOT PER HUNTER, WCSC AND STATE 1947-1949 Cocks Shot per Hunterl’ Year Ratio of “(:30 8';th State to "08C 1947 . 1.69 1.76 1.04 1948 1.65 1.79 1.09 1949 2.09 2.24 1.07 Average 1.81 1.93 1.07 1 State and HCSC indices are not directly comparable. (See text, Section 2.6) 30 obtained on a voluntary basis.1 It is possible, for exawle, that in a voluntary system there is a tendency for the more successful hunters to report their good luck, which would cause an inflation of the computed kill. On the other hand, there might be a tendency for more unsuccessful (and therefore disgruntled) hunters to report their 22.5 met; this would deflate the computed kill. Hunters who belong to sportsman's clubs are not likely to be an unbiased seaple of Michigan's over one-half million small game hunters. Possibly club members are more likely to send in their report cards than the average small game hunter. So none of these samples is random. To shed some light on how close these tallies are to actual kill, we need to comare them with an actual measurement of pheas- ants killed on sanple areas. Although such areas are rare, the Department had two study areas where actual kill was measured--the Rose Lake Wildlife Experiment Station near Lansing, and the Prairie Perm in Saginaw County. Rose Lake2 has varied in size from one to two thousand acres, so it is relatively small. It is difficult to say how it compares with the rest of the state's pheasant range. The station lies astraddle the Clinton-Shiawassee County line; Table 2.7 shows how the average number of birds killed per 100 acres for a 10-year period 1Despite the fact it is a misdemeanor to fail to submit the Department's report card, the law was not enforced. Hence, in fact, the system was voluntary. 2Thenose Lake Wildlife Emeriment Station is described by Allen (1941). Researchers obtain careful measurements of pheasant kill each season, as well as other pheasant population estimates during the year. 31 o.cs o.c~ m.n ¢.o 0.5 omuum2< m.mm n.5w n.an h.¢m ¢.ou Henna m.n m.~ m.n mema n.¢ ¢.N H.¢ weed o.n n.~ c.m mead o.n o.~ n.n mama m.o m.~ c.“ neaa o.c m.n u.» ¢¢a~ o.» «.0 e.» mead «.ma o.oa m.m m.HH a.» «ems w.- o.o~ o.“ «.5H H.a gems m.o o.- m.¢ m.o~ H.n oema o.a o.mH mama a.m m.¢~ mama m.s n.s mama .oo sandman such .00 sooneswanm sowusum .mxu .oo concede user 338.. , . =5: 9.3 Son condom wcuuoaw means: nouu< cod «on vandal exooo . wank—woo UZHE< ~.# man<9 4.5 62 little from survey to survey. Further, results of surveys are al- ways comared to other surveys by carriers; so the unit, whether it be time or linear distance, is i-aterial. Finally, even though routes might vary 2 miles (4 per cent), we have no reason to believe that time (hours on the route) is any less valid as a unit than miles traveled. For nearly 30 years the unit of ‘measurement of’deer counts made by Department personnel has been "time spent in deer territory" rather than miles traveled. Surveys [:1 Conservation Officers Michigan conservation officers (hereafter referred to as of- ficers) are carefully selected and well trained. Thy are inter- ested in their work and are. cooperative, which makes them valuable observers. The nature of their duties and their daily routine provide a consistency of observations. The fact that they are Department eqloyees made it easy to arrange for them to record pheasant observations in any fashion and period required. In some years, officers have recorded daily pheasant observations for nine months of the year. In many instances, officer counts coqlement the carrier surveys-~each supplying what the other lacked. With only one or two officers per county, data for small units were often lack- ing in sane size-which the carriers' surveys made up for. On the other hand, carriers could not be asked to make counts for long periods of time, or during the Christmas rush, for examle; the officers could be. The number of officers in pheasant range has varied from year to year. In 1946 their numbers were low due to post-war 63 adjustments. In 1950, however, there were about 55 officers in the 34 counties of the Department of Conservation's Region III. Region III is composed of three districts. Since reports of officers were handled through administrative channels, their data were tabulated by these districts. Figure 4.3 compares Region III, including these three districts, with the 38 coun- ties that have been designated as primary pheasant range. Pour counties on the northern edge of pheasant range in another ad- ministrative region were covered by carriers and not covered by officers. As in the case of the carriers' tabulations, daily pheas- ant observations have been tallied in terms of units of time, rather than linear mdleage. This was a necessity, since officers record mileage semddmonthly, usually by reading their car speed- ometers. Asking (as we have tried) for daily mileage resulted in unsatisfactory tabulation. Many neglected to mention it, and many others had to estimate it. Since it was not part of their official routine, it was neglected. In interpreting observations by two- week periods, however, mdleage may be used, since that figure can be assumed to be reasonably accurate. Even so, there is consider- able evidence that officers' observations of birds per unit of mileage is not so useful as observations per unit of time (i.e., observer-day). Officers' duties are seasonal, and at certain times they may be checking for fishermen on lakes or walking trap- lines in completely different habitat--so car mileage would be meaningless. 64 I, ARENAC " , HASON LAKE osccou CLARE oLAowm ‘ s’ 2 / 6‘s" nunou 3 w 5! I occAuA uccosu nSAacLLA moLAuo : NtwAvoo A | ‘ TUSCOL SANILAC '\ r... uONTCALMl GRATIOT “Gm“ .. I \ Amt GENESEE mm SAINT I '. OTTAWA IONIA cunt N E1 f‘ cum I I f“ l f I , i ‘J 7 0AA1Auo “to“ : ALLEGAI BARRY EATON moms LIVINGSTON I L“ o: _ SYCLM V“ BUM" KALAHAZO4 CALHOUN JACKSON WASHTENAW WAYNE CANADA st l / CASS ‘ BRANCH HILLSDALE LENAWEE sonnet """ "—-.' —ol—beJo-5Eepmu mm-m "/ LAX: I N ' N A .—.. ee—ee— e—e r OH ERIE Fig. 4.3--Officers' administrative districts. 4.6 65 Surveys by Farmer Gosperetors In the spring of 1948, the names of over 600 farmers who were interested in conservation were obtained from county agents, of- ficers, or district game managers who knew them personally. In the spring of 1948, 1949, and 1950 the farmers were asked for in- formation on nests and broods discovered during spring work, particularly while plowing sod or mowing hay. They have been a good source of information which in the past was difficult to ob- tain. For examle, studies of clutch size, to be statistically valid, must be determined from a large number of observations. In Michigan, Rose Lake and the Prairie Farm combined had recorded clutch sizes on less than 100 nests during the 13 years the station had been in existence, and the 4 years the Prairie Farm had been a study area. Yet in each of the 3 years the farmers cooperated, they reported more than 100 clutches. The number of nests in hay and sod are thought by some workers to be indicative of net pheasant production for any year. Finding pheasant nests is extremely difficult. Farmer cooperators have given us good information on numbers of nests they found per acre-- data that would otherwise have been difficult to get on an exten- sive basis. The farmer cooperators appear to be an unusually interested and responsive group. So far they have been canvassed only for performance data (e.g., actual number of nests found per definite number of acres plowed or mowed), which can be used objectively. The group may be large enough, however, that they could be asked for more subjective information, such as number of broads they see 4.7 66 on their farms each winter. I atteqted this, but was not satisfied that I could convert their returns into usable information. Never- theless, I feel this possibility should be explored further. mm m Kimball (1949) reported on a technique for extensive analysis of the cock pheasant population in the spring by use of a crowing- cock survey. Basically, this consists of running a 20-mile route starting one-half hour before sunrise. Bach mile a stop is made and all pheasant crows heard during a two-minute period are re- corded. At the conclusion of each route the total or average nus- ber of calls is calculated, and constitutes an index to the abundance of cock pheasants along that route. In 1948 I experimented with the.technique of the crowing-cock survey in sale areas, and in 1949 set up a system of routes covering the 38 counties in primary pheasant range. These routes were not picked at random. Rather, they were set up geographically to cover pheasant range. An attespt was made to put one route in most counties in pheasant range. Where one county obviously represented two types of range (Lenawee County, for exaqle), we tried to set up two routes, one in each type of range. This was not always possible, due to manpower limitations. We tried to run each route at least three times during the spring. If weather conditions prevented accurate counts they were repeated up to four or five times. This usually resulted in at least one good count on each_ronte. We selected the maximum figure for each separate survey as the value for that route. 4.8 67 Routes were run by biologists and wildlife student aides. Considerable care was taken to train and select these men. In- sofar as it was practical, a different person was used on each of the three runs on each route each spring to minimise individual differences in hearing. Individuals whose hearing was not well tuned to the frequency of a pheasant cock's crow were not used. Since geographical coverage was good, yg_a_r_ to may; cowarisons of crowing-cock averages should be reasonably valid as an index to the state-wide cock population. Since routes were not randomly selected, however, coqarisons from £53 to ge_a must be made with caut ion . Surveys by Game Biologists Came biologists and part-time student assistants on the project helped in many ways, although there were so few of them that their surveys could rarely be called extensive. In some cases, however, (e.g., crowing-cock counts) we relied heavily on them. At other times biologists could collect data at the same time that other extensive surveys were being run, to add to, or appraise, the extensive-survey data. Biologists and students provided all the manpower for con- tacts of sportsmen for hunter-performance data during the hunting seasons. There were many other instances where biologists were responsible for collection of data extensively. Aging of pheas- ants and counting of crowing-cocks, for exaqle, had to be done by trained people, and only through the use of all available biologists could we get enough data over large enough areas to be 4.9 68 meaningful. Finally, we depended heavily on biologists for advice on the type of information we should be gathering, the timing of surveys based on the phenology of their districts, and on unusual circum- stances that might be a clue to what was happening to pheasant populations as a whole. Smagy g; Conclusions Linduska (1947) described the objectives of the extensive survey, and the first carrier and officer surveys run in 1947. Surveys by sportsmen proved valueless and were abandoned. Per cent returns were low and they could not, as a whole, be re- lied on to age pheasants accurately. The carriers proved to be a willing group, and were used for three surveys a year--spring, sinner and late fall. Officers could be used for longer periods (all stnaer or winter) and their data were numerous enough to be valid for several indices. The carrier and officer surveys nicely coqlement one another. Officers cooperated over long periods of time, but their operations lacked bulk. Carriers furnished large eagles of data that the officers could not match, but their surveys were infrequent and for short periods. Farmers were very cooperative and provided extensive data on clutch size, brood sire, hatching dates, timing of certain agri- cultural practices, and nest and brood density data. Biologists were used for crowing cock counts, hunting season contacts of hunters and for examinations of birds for biological data. They also made some counts simultaneously with other 69 extensive surveys . During the five years (1946-1950), about 60 extensive surveys exclusive of hunter kill reports were made. They involved close to 10,000 individual reports, involving many million miles of driving and observations of close to a million pheasants. Such extensive surveys are inexpensive to run, and involve very little cash outlay. When the limitations of extensive sur- veys are recognised, they are an excellent source of data at a minimum of expense. Chapter 5 SPRING POPULAIIONS 5.1 Introduction The crowing-cock survey offers biologists a good method for censusing cock pheasants. But estimates of spring breeding popu- lations from the crowing cock count are dependent upon the sex ratio of the spring population. Moreover, crowing-cock surveys are limited by the availability of biologists. So there was a need to attempt to develop other spring surveys-~to try to determine breeding season sex ratios, and to try to find an easier method for censusing cocks and hens alike. In the spring the habits of cocks and hens differ. Cocks display, and hens become progressively more secretive as they begin to nest and become broody. So the relative observability of the two sexes differs, and probably shifts as the spring progresses. Determining true sex ratios, then, promised to be a difficult problem. But a relative sex ratio from spring to spring‘might have some use, if we could find a way to time the counts so they could be made at the same time (phenologically) each spring. To get this spring population data, I set up an extensive crowing-cock survey system and a system of extensive roadside censuses to be run by the carriers. 70 71 5.2 growing-cock Surveys‘ggg Carriers' Surveys The crowing-cock survey as it is used in Michigan was described in Section 4.7. The location of crowing-cock routes is shown in Figure 5.1, and results of the counts are shown in Table 5.1. The latter are tabulated by study area. Relative abundance of pheasants from area to area roughly follows our other data on pheasant numbers (e.g. Area 1 high, Area 4 low'populations). flhile sample size of data by area is rather small, this appraisal of the spring cock population might offer a partial basis for determining unusual winter mortality in an area, and for gaining insight into relative rearing success for the areas. In April, 1948 I asked the carriers to make an experimental one-week survey. They recorded the number of pheasants seen while driving their routes for a six-day period. I attempted to time the survey so it would come at the height of breeding activity. At the time it appeared to be a good choice; crowing activity was good and breeding seemed to be in full swing. But there was no method for timing the count since no state-wide crowing-cock survey was run that year. The carriers reported about 1,700 pheasants. Analyzing the data by study area showed fair correlation with what we knew'of pheasant populations, so the survey showed some promise. Officers were not asked to make an April survey. Judging from their winter counts, the officers were too few'in number to gather an adequate sample. The April count had to be relatively short, since pheasant observability was shifting rapidly. More- over, the officers were making daily observations for the entire 72 ARENAC { mm LAKE OSCLOLA CLAnc GLADVHN 9’ A 2 _,__1 6‘3 URON m 5» L J OCEANA MECOSTA ISABELLA.MIDLAND Nchvoo 1 Cf ‘ COL mu MONYCALJCCATIOT ‘5'" H Q “(N7 GCNESEE LAPEE {I 07”” IONIA CLINIO JQEJ CAN": 2.: C2. M OAK AND mucous “LN M v [A6 A L TON L as: srcun NAL NAZOO ( JAcAs ASNTENAN mm: Z, 4” _;>.CANADA ST JOSEPH “0.2).. ,/‘LAKE ERIE Fig. 5.l--Location of crowing-cock survey routes. 73 summon N.uH n.N~ Q.HH h.@ 0.5 %um6«um . H38. O.HH MN ~.N~ on Q.H~ on N.a on «.0 on mmuu< n Q.N~ N m.NH N N.NH N m.o N w.m N m w.¢ m m.n n H.@ m N.n n o.¢ n c a.¢~ o n.¢~ o N.N~ o o.H~ o ~.w o n m.c~ n o.¢~ n ¢.oH n N.NH h h.NH h N ¢.NH N m.N~ o“ o.NH oa 5.0H OH w.m OH H msouu nausea e395 mouse: usouo season msowo season 23.5 nausea no no .oz «O «0 .03 mo no .02 Mo mo .oz no mo .02 6 oz O >‘ 0 oz 0 >< . a O >< 0 oz 0 ’< I a O >< some nnod NnoH Hmoa onoH mead means: 95. non muse: ezeo mo none—oz 3322 mwnhubm MUOOIUZHzomU no rmu=m quumm .mduumd<0 MO ruu=m qummm 2H mmuuumummmo moHHuo= ensue n n swam unwwu woman N - can“ h>mu= mound e . anon h>uom I hue moouo N I seem h>oum mun mun mun in man swam .ua nouuo n n can: h>oom ou .un inn b5 / .05 /, noun H u can: mbuom nevus n I seem m>wu= muons m I seem h>uu= mmouo n u :«o& .uq .05 _ _ _ _ _ _ be 0 0 0 0 0 0 0 5 0 5 0 5 0 5 3 3 2 2 1 1 ouoauuuo hm comm moooun deuce 2m. U A m. 7n 9 1 5 2.... n. B n 3 2 1 2 .4, mm Va 71 In J D B 1 1 Fig. 6.3-~Carriers' daily brood counts compared with precipitation. 94 is not well founded. I could find no evidence from these extensive counts that annual changes in brood size had any appreciable effect on total pheasant production. Since brood size would be expected to vary with age of the brood, and since broods are produced later (or earlier) some years than others, carriers and officers were asked to estimate the approximate age of the broods they observed. This posed a technical problem in instructing large numbers of untrained cooperators by correspondence. This was done by specific instructions and comparisons with other birds, such as robins, quail and crows, and by the use of visual aids. I do not know the actual average age of l/4-grown chicks, for example, as they are recorded by carriers and officers. But one can expect that with the large bulk of observations and about the same group of cooperators each year this actual age, whatever it is, should be the same from year to year. In addition to separating broods by age, I felt it was also necessary to compare brood sizes which were determined during a rather short period of time. Even though the chicks are aged correctly, brood sizes obtained by lumping data from the three months of June, July, and August, must be used discriminately. For example, in 1946 carriers observed 357 1/4-grown broods in the first half of June, for an average reported brood size of 8.4. In the first half of July that year, they observed 525 l/4-grown broods for an average reported size of 6.7, a difference of 1.7 chicks! This difference may be real, or it may be in part due to differences in cover conditions and hence visibility of the broods. 95 Finally, I felt that any study of brood sizes should involve large numbers of observations. With an average which could be expected to be somewhere around 6 to 8 chicks, with sizes varying from 1 to 20, the variation might be expected to be large. The sizes of 8,787 broods observed by carriers in late July are shown in Table 6.1. Brood size does not appear to shift appreciably from year to year. The differences the table does show could be largely a reflection of sampling variation. The larger spread shown by 3/4-grown broods is suspect because phenology from year to year might cause a differential due to chicks maturing and leaving the brood. Ignoring 1946, the spread is only .41 chick, comparable to the l/Z-chick variation in quarter and half-grown broods. There is one obvious reservation to the conclusion that brood size does not change significantly--there is no way of know- ing how accurate the carriers' counts are. The final proof of their accuracy'must lie in performance. This is discussed in the next chapter. Some insight into the reliability of the carriers' brood sizes might be provided, however, by inspection of the frequency distribution of their observations. In Figure 6.4, the frequency distribution of observations of 1/2-grown broods for four years is graphed. With no attempt at this point to evaluate this distribution statistically, there is evidence that the carriers are not just guessing at observations. The curves are roughly similar from year to year. There is not much evidence that they are prone to lump observations in the TABLE 6.1 SIZE OF BROODS REPORTED BY CARRIERS 96 Year 1f4 Grown 1/2 Grown 3/4 Grown All Broads 1946 6.23 1 6.21 5.97 6.14 (497) (899) (654) (2050) 1947 6.65 6.48 5.38 6.36 (286) (335) (128) (749) 1948 6.45 6.38 5.08 6.12 (565) (804) (379) (1748) 1949 6.22 6.10 5.08 5.88 (568) (957) (509) (2034) 1950 6.67 6.63 4.97 6.34 (774) (1031) (401) (2206) 5 Year Av. 6.44 6.35 5.36 6.14 .45 .53 1.00 .48 Tot . Spreafl 1Figures in parenthesis are number of broods on which each brood size is based. Number of Broods Observed ~\ ,. $1 I! 4 60- I ,’ \ \ [I ‘~ F \ .8 I ’1 \ I \ \ s.s '. . \ .0 s. .' .. \ e. .0 ' 5's, s . '.’.9!?-' ~.,...--..\'/\ '0. V "O.‘.‘\ ‘\ O. O s' a.“ ‘ a..\\ is : _\ O. \ 0' he). has 1 1 e1. e11. 1 14, l Alleelle l "'.4,' J. _ ’ c 0 5 10 15 Number of Chicks in Broods e I Fig. 6.3--Frequency distributions of sizes of half-grown- broods observed by carriers. 97 6.5 98 "5" or "10” categories, as so often happens (although there is a slight tendency for even numbers to be higher than odd). Further analysis of brood size could be pursued; logically, brood size should be compared by study area. That is not in the province of this study, however, since we are interested in brood size principally for its effect on estimates of total popu- lations. L. L. Eberhardt analyzed brood sizes based on the data in Table 6.1, as well as similar data from later years, and concluded that brood size appeared to have no significant differ- ence from year to year, but did have significant variation from area to area.1 Even so, there is still no way of knowing whether. these differences are real life history phenomenon, or merely differences in simple observability of pheasants. There are obviously rea1_differences in cover conditions between the flat open land types of the lake-bed clay country and the rolling, brushy types in southwestern‘nichigan. Percentage _9_f. fling Without M There has been a suspicion in Michigan that loss of pro- duction has been fewer broods produced for some reason or another, rather than differences in the degree of attrition of chicks from broods. The studies of brood size in the previous section support this suspicion. During these July brood counts carriers were asked to record the hens they saw which apparently had no broods. Those hens IUnpublished data in one Division files. 99 which have not hatched a brood by late July are extremely unlikely to contribute many young birds to the shootable fall population. A cock hatched on the first of August would hardly be colored enough by mid-October to be easily recognizable in the field as a cock. Data were tabulated as percentage of hens seen that had no visible broods. For the five years of this study, this percentage was as follows: 1946 411 1947 471 1948 372 1949 351 1950 371 For the two years with poorest pheasant production, 1946 and 1947, these percentages were highest, so this percentage may reflect production in a general inverse way. Its specific use as an indicator of production, however, is doubtful at this time. Observability of hens with or without broods may vary, so this percentage may be an index rather than absolute. The best evalu- ation of this percentage must wait until we have a reliable index to true productivity based on true fall age (and sex) ratios. 6 . 6 gonclusions Brood counts increase at a predictable rate during the summer period. Counts are apparently not appreciably affected by rain- fall. On the basis of nearly 9,000 observations of broods by carriers, no significant difference in brood size from year to year could be detected in a five-year period. The percentage of hens without broods observed may reflect good or poor production years, but is probably not usable to calculate specific productivity. 7.1 7.2 Chapter 7 PREDICTION OF FALL KILL FRON.SUHMER.BEOOD COUNTS Introduction The principal reason for the search for an accurate measure of pheasant populations in mid-su-er was to find a method for predicting fall populations, as a basis for setting hunting season regulations. During the first fewryears of the summer brood counts, there appeared to be general correlation between increase and decrease of the brood counts, and increase and decrease of the kill during the corresponding fall. This general correlation seemed to exist for the study areas as well as for the entire stltO. In 1949, with four years of data to work'with, a series of 16 different correlation coefficients were calculated, analyzing the data on the basis of county, area, and year, and weighting the areas on the basis of size. values of ”r" for these correlations are shown in Table 7.1. These values are not particularly per- tinent not useful, except to show that excellent correlations existed, even on the individual county level; none was below .65 and 9 of the 16 were above .90. Correlation of Carriers' Brood Counts with Cogputed Kill The regression of computed kill on broods seen by carriers by study areas for the four years 1946-49 is shown in Figure 7.1. 100 101 TABLE 7.1 VALUES 0! CORRELATION «EFFICIENTS (1') FOR 16 COMPARISONS 0F COMPUTED KILL WITH CARRIER EROOD DENSITY INDICES D‘t‘ L‘V‘I 60:3:1:ted 23ingf Velzes County 1946 27 .99 1947 28 .95 1948 38 .65 1949 37 .85 1946-49_ 130 .79 Year Area 1 4 .98 Area 2 4 .65 Area 3 4 .97 Area 4 4 .99 Area 5 4 .74 Area 1946 5 .97 1947 5 .88 1948 5 .93 1949 5 .90 1946-49 20 .91 Area (weighed) 1946-49 20 .93 Computed 'Cock Pheasant Kill per Square Mile (y) 102 70 y . 3030 * 7.328 1 I l 1 1 l 1 l J_ 1 2' 3 4 s 6 7 8 9 Broads Seen per 10 Carrier-days“) Fig. 7.1-~Regression of computed kill an carriers' brood density indices for study areas, 1946-49. 103 This regression line could obviously be used to predict fall kill from the carriers' brood counts. The four years used in these correlations represented rela- tively low pheasant populations, however, and assumed a straight- line relationship. The regression formula shown in Figure 7.1 might not necessarily be valid for predicting kill an the basis of carriers' brood counts during years of higher pheasant populations. Following 1949, carriers' counts in July were continued each year in the same fashion, and at the same time the pheasant kill was coquted from hunter report cards through 1956, when the system was discontinued and replaced by a sampling system. On the basis of 11 years of data, the relationship between carriers' brood observations and computed kill the following fall can best be shown by the regression illustrated in Figure 7.2, where computed kill is plotted against the logarithm.of broods seen per lO-carrier days. The correlation coefficient is .978-- an extremely close correlation. Since there is an unknown saqling error in each of the measures involved in this correlation, this "r" value may be less than the true correlation. Neverthe- less, its usefulness in predicting fall kill from sus-er brood counts is obvious. Table 7.2 shows the detail in support of Figure 7.2. Figure 7 .3 coqares the coquted kill with broad density by area for the 11 years. There is, of course, more spread since the areas involved are smaller. Because of the likelihood of dif- ferences between areas (such as broad size mentioned in Chapter 6 and discussed in the next section), it is iqractical to calculate 104 1400 " 1200 '- 1000 y = 44 + 1275: 800 600 400 Cosputed Kill in Thousands (y) 200 l 1 1 g l A L 1 1 J .100 .200 .300 .400 .500 .600 .700 .800 .900 Logarithm of Broads per 10 Carrier-days (1:) Fig. 7.2--Regression of computed kill an logarittm of carriers' brood density index for primary pheasant range, 1946-1956 mm: 7.2_ RECRESSION 0F CONFUTED RILL 0N LOGARITEH 0F CARRIERB' EROOD DENSITY INDICES Broads per Log Broads Kill Year 10 C. D per 10 C. D. In Thousands “ (X) (Y) 1946 5.04 .7024 904.4 1947 2 . 25 . 3522 452 .9 1948 2.97 .4728 632.7 1949 3.61 .5575 864.0 1950 3 .60 .5563 797 .5 1951 5.74 .7589 943.7 1952 5 .49 .7396 947 .9 1953 7.27 .8615 1,144.9 1954 7 .68 .8854 l ,178 .4 1955 7.86 .8954 1,230.7 1956 6.74 .8287 1,101.0 Sins 7.6107 10,198.1 Means . 69188 927 .1 00 Y s 927.100 - 882.348 + 1275.29! r .-. .978 105 106 801" 0Areal,3,5 ' oAreaZ AArea4 ‘ 70? o 0 ' o 0.0 '0 "60h- 0 2: °- 0 s 'é' ° ' ° :50“- O . 3 O O s o- VJ O. 0 E401. ” ' ,. 2‘. ° . ' O :1 ° ,. 1330.. e 3 O O :1 g s 0 AA s 201" A A A A A 73 10— A A A 111 1 1 1 1 .14 1111 4 .8 1.0 1.5 2 3 4 5 .6 7 8 910 15 Broads Seen per 10 Carrier-days (x) Fig. 7.3--Coqarison of computed kill with logaritlm: of carriers' brood density index for study areas, 1946-1956. - 7.3 107 the regression on the basis of these points; rather, regressions should be calculated separately for separate areas, or groups of similar areas, when enough data have been accumulated. To illustrate this likelihood of differences in regression between areas, the points for the two most diverse areas--2 and 4-- are identified in Figure 7 .3. Regression formulae calculated for each would be quite different. On ths basis of the regression shown in Figure 7.2, and with the benefit of hindsight, one can calculate how accurately the kill might have been predicted from carriers' brood counts for the 11 years involved in the regression. Table 7.3 shows the deviation from the regression for the individual years . This method of predicting fall kill may appear disarmingly siqle. It by-passes s amber of factors or considerations, or makes a nmsber of assmtions which are not particularly proven. The proof of the system is in its performance. Six of these factors are discussed briefly below. It must be remembered that the siqle fact that the system works is not proof of any of these assulqtions. I do not know to what extent errors introduced by one factor might be cmensated for by another. Nevertheless, the fact that none of these considerations has seriously skewed the regression curve in the 11 years involved lends support to tentative conclusions regarding them. In essence, one must assume a consistent relationship between the broods present in late July and the October population from year to year. If the following factors are not cogenssting, then TABLE 7.3 108 ERROR.IR PREDICTION OF’COHPUTED KILL FROM CARRIERS' EROOD DENSITY'IRDICES L A Kill in Thousands Approx. Error in Year Per Cent of Predicted Computed Computed Kill 1946 935 904.4 32 1947 495 452.9 81 1948 645 632.7 22 1949 750 864.0 152 1950 750 797.5 61 1951 1,010 943.7 62 1952 985 947.9 41 1953 1,140 1,144.9 01 1954 1,175 1,178.4 02 1955 1,180 1,230.7 42 1956 1,095 1,101.0 1% Av. 42 109 each, in turn, must be quite consistent from year to year. 1) Let; m1; mortality. Following grain harvest in mid- July, when most chicks are at least half-grown, mortality to young caused by weather or food shortage should be at a minim. Bar- ring an epizootic or similar catastrophe, mortality would logi- cally be expected to be consistent from year to year.- This is in sharp contrast to the preceding period, from the breeding season through hatching, when weather and even food conditions could con- ceivably alter mortality radically from year to year. The fact that the size of l/2-grown broods observed by car- riers does not change appreciably from year to year would suggest that mortality to chicks in the early smr, when chicks are small, must operate principally on whole broods rather than indi- vidual chicks. Thus, our conclusion that loss of pheasant pro- duction seems to operate on the entire brood or the hen before she brings off a broad rather than attrition to individual chicks. Small game hunting license sales and resulting hunting pressure in Michigan are high enough that pheasants are probably hunted to the point where a 10 per cent change in hunting pressure would not greatly change total kill. License sales changed less than 5 per cent each year in 6 of the 11 years, and in 2 other years the change was less than 8 per cent (see Figure 2.1). The year 1946 was a striking exception; sales were 25 per cent higher than in 1945 and 22 per cent higher than in 1947. This increase is generally credited to the interest of returning servicemen in 1946, many of whom may have had a particular interest in hunting that 110 year which dissipated in following years. In many ways, the 1946 data were more at variance with the ”average" than other years. Season length and bag limit were reduced in 1947, 1948 and 1949 (see Figure 2.1). About 70 per cent of the present 22-day season's total kill usually occurs during the first two days and the first weekend. So even the lz-day season in 1947 and 1948 was probably enough to harvest the pheasant crop, and the total kill was probably but little less than it would have been had the season been 22 days long those years. This is especially true since during these three years of restricted seasons pheasant populations were low. Regulations have specified various opening hours, particu- larly on the first day or two of hunting. This has apparently affected total kill but little. Analysis of the Bass Lake data, where data from previous years were available for coqarison, did not show any change in total season kill traceable to a change in opening hours (Black, 1950). Hunting conditions are popularly supposed to have consider- able influencs on the harvest of cocks. The conditions most regularly mentioned are weather (principally rain, temperature, moisture conditions on the ground, snow cover and wind) and cover (amount of standing or unharvested corn, lushnsss of the season's growth, and whether or not there have been frosts heavy enough to knock down some herbaceous growth). Although hunters may fancy that these things affect their individual success, I was not able to detect any measurable affect these conditions have on total state kill for any season. Quite probably these conditions are 111 less influential than the average hunter supposes, and quite probably the conditions vary nuch less than he supposes. 3) £59. r_a_§_i._9_s_ 2; 9935 gill. Deter-ninetions of ages in the, fall kill show a shift as the season progresses (see Chapter 8). True age ratios of the fall cock population are unknown. Yet a year of good brood production will ordinarily have a higher per- centage of young birds in the fall than will a year of poor pro- duction. Since the fall kill is so dependent upon the young cocks of the year, one night suppose that changes from year to year in the percentage of young cocks in the Isle seg-ent of the popu- lation will upset this correlation. The effect of a change in age ratio need not be as influ- ential as one night suppose, however. It is con-on to have very disparate observed age ratios in the kill--perhaps as high as 1 adult to 15 or even 20 young. In these instances, adults would coqose fron 5 to 7 per cent of the kill. Thus, though a chang- ing nuaber of adults caused a shift of age ratio from 1:15 to l:20--a 33 per cent change in nmbers of adults--the net change in the kill would be only 2 per cent. If, of course, the number of adult cocks stayed the seas and the shift was caused by a dif- ferent nuaber of young, this would be a net change of about 33 per cent-~but that would be measured in the carriers' brood density index. It may well be that the net percentage gain or loss of the adult proportion of the kill is not large in any one year, and hence does not greatly influence the correlation. 4) §_i_._r_e_ o_f_ gm. Brood size apparently does not change appreciably fran year to year in Hichigan.($ection 6.4). 112 As a further check against the influence brood sise night have, correlations of brood size with carriers' brood density indices and with coquted kill for eleven years were calculated (Table 7.4). No significant correlation was found. 5) Precision and accuracy of M surveys _an_d coguted ki_l_._l_. There is no clear-cut neasure of the precision of each of these population neasurenents now available. Each is a saqling systen-- each has a seqling error. Again, we lust fall back on the per- foraance of the systen to deteraine its usefulness. The likelihood that the coquted kill is a useful index to actual kill was dis- cussed in Chapter 2. The accuracy of the brood density index is, in turn, deterained by how accurately we can predict the kill fro- it. 6) gi_a_ing g_f_ 52; E229. survey. The isportance of tining brood surveys was discussed in Section 6.3. Deter-lining the pheno-' logical status of pheasant brood production is extra-sly difficult. The dates in July that I picked for the carriers' surveys each year were carefully weighed in the light of that spring's phenology. we do not know precisely how phenology affects pheasant breeding. ' But if the peak of cock crowing, for exane, appears to be a week later one year than another, it would be reasonable to try to run the nail carrier counts one week later. The opening of the pheasant season was changed fro- October 15 to October 20 in 1952. The population is undoubtedly a trifle * lower on October 20 than on October 15. issuing the 1.65 per cent daily expected increase in broods seen by nail carriers (Section 6.3) is valid, the 15 per cent TAIL! 7.4 COIIILAIIOIS O! BROOD SIZE AND THO POPULAIION INDICIS 113 Broads Seen Kill in per lObCarrier Average Year Thousands Days Brood Size (*1) (x2) up 1946 904 5.04 6.4 1947 453 2.17 6.3 1948 633 2.85 6.2 1949 864 3.63 5.9 1950 793 3.60 6.3 1951 944 5.74 6.2 1952 948 5.49 5.9 1953 1,145 7.27 6.1 1954 1,173 7.63 6.1 1955 1,231 7.36 5.9 1956 1,101 6.74 5.8 13,133 g -.546 r05 . .602 l3|:2x3 a -.474 1'05 3 .602 114 maximum error in our predictions (Table 7.3) could have been ac- counted for by a lO-day timing error in mail carrier counts. All of these seven variables are capable of introducing error. Some, such as hunting regulations, may vary with population levels and be automatically coqensated for; others may cogensate each other. The sum total of these errors, however, must be contained within the error shown by the regression in Figure 7.2. Cor- rection of the possible errors mentioned above can only refine this regression which. as it now is, appears to offer good in- formation. In the final analysis, one strong proof of both the kill figures and the carriers' brood surveys is their consistently small deviation from the regression. It would quite likely be re- warding to try to coqensate for some of tlmse errors--particularly timing of the counts. But to be able to predict fall kill from a su-er count with an error averaging 4 per cent is a rare and satisfying experience for the game manager. 8.1 Chapter 8 FALL POPULATIOUS Introduction In Chapter 2 the computed kill figures were appraised, and in Chapter 7 it was shown that there was an extremely close relationship between the number of broods present in the summer and the fall kill. This demonstrated that the fall kill is almost directly dependent upon the brood production the previous summer. Adult birds contributed either so nmall or else so 4 consistent a proportion of the kill that they did not seriously affect this relationship. It follows then, that total kill, accurately determined, is a good index to the fall population. If we knew’the fall sex ratio, and if we knew what percentage of the fall cock population was harvested, it would be possible to calculate the fall popu- lation. This chapter deals with other indices to the fall kill, attempts to determine.pheasant numbers by other than total fall kill computations, and attempts to determine fall sex and age ratios. Preseason Sex Ratio Surveys In the fall, just prior to the hunting season, the sex ratio of a pheasant population is usually close to 1:1. Despite the 115 116 fact that pheasants are polygamous, and that in a hunted popu- lation a sisable percentage of the cocks are removed each fall, young of the year about equally divided as to sex are the pre- ponderant part of the fall population. ‘Horeover, the disparate sex ratio of adults in the winter is probably brought closer to 1:1 during the sus-er by a higher mortality of hens, due to the increased hazards of nesting (mowing machines, increased v’ulnere- bility to predators, etc.) . £95 3.33.3 observations _og gyening _d_gy _o_f hunting _s_e_g_s_o_n. The most couon attempt to get a preseason sex ratio has been from sight observations of pheasants by hunters on the opening day or days of hunting seasons. Allen (1942) devised a system for calculating preseason populations, in which opening day sex ratio observations played a part. while such observations have some merit, they have two drawbacks. (1) Observations col- lected from a large number of hunters are not particularly accurate, especially when large numbers of pheasants are observed in a day. (2) The removal of cocks by legal hunting during the observation period, even though it be for a period as short as one day, prejudices the ratio in favor of hens. This is a serious handicap when opening day pressure is heavy, as it is each year in almost all of Michigan's primary pheasant range. It has been a common occurrence for one-third of the total pheas- ant kill to be taken on an opening day. On the Prairie Farm, for example, the percentage of the total kill that was taken opening 117 day for a number of years was as follows: (Shick, 1952) 1937 1938 1939 1940 1941 1942 192 381 501 33% 351 302 Similarly, during the eight-year period 1951-1958 at the Rose Lake‘flildlife Experiment Station, an average of 34 per cent of the total season pheasant kill was taken on the opening day. - In Table 8.1 observed sex ratios on opening days at the Prairie Farm and Rose Lake are compared to the calculated preseason population for a number of years-~some of high pheasant popu- lations, some of low. There does not appear to be a correlation between relative abundance of birds and the disparity of the sex ratios. It is likely that there is a considerable error in these opening day observations. Preseason roadside counts. In 1948 officers were asked to keep track of the pheasants they saw from September 15 to October 15 when the pheasant season opened. Since there were certain to be many birds in broods too young to be sexed, observations of these young were recorded separately. Half of these young birds could be assumed to be cocks, half hens. The total of such observations was halved, and half added to the cock tally, half to the hen. Results are shown in Table 8.2. These results are implausible. The total number of birds ' observed per mile of travel dropped far below the July brood counts, indicating that the birds were relatively more difficult TABLE 8.1 OBSERVED SEX RATIOS ON OPENING DAYS Prairie P'arm1 Rose Lake2 Calculated Calculated Year Opening "Preseason Opening FPresaason Day Cock Day Cock Sex Ratio Population Sex Ratio Population (Hens/Cock) per 100 A. (Hens/Cock) per 100 A. 1937 1.2 13.7 1938 1.4 21.4 1939 2.0 20.4 1940 1.6 17.5 .9 18.0 1941 1.0 22.9 1.3 31.7 1942 1.4 19.9 1.3 16.7 1943 1.3 11.6 1944 1.0 1536 1945 .7 7.3 1946 1.3 5.2 1947 1.2 4.4 1948 1.4 6.2 1949 .9 6.5 1950 .S_ 5.2 lsma (1952) . 2Rose Lake files. 118 119 an. o¢a.~ een.n no“ ono.a one.n eee.¢n no-e .uoo .3. and; 9&3 «um «um m8?" wacoe onuna .unom ; Sufi 3.08 9.3.8 «no: 938 3000 you one: Houou. 3.3.5 ouuem New codex. open eczema—o 35¢an N.» was mmmloho rm mchhasmnmno gamma gm 120 to see at this time of the year. Even at this date, pheasants appear to be segregating by sex, to some degree. In many broods so young that the cocks were only partly colored, it would obviously be very easy to mistake a young cock for a hen. Shick (1952) was unable to obtain a satisfactory preseason sex ratio from field observations on the Prairie Pena. Stokes (1954) attempted to obtain a preseason sex ratio on Pelee Island in the late 40's. Three different types of sampling he tried resulted in three widely differing sex ratios, none of which seemed plausible. He laid part of the difficulty to the fact that cocks were engaging in fall sexual display at this time of the year, and hence were disproportionately obvious to the road- side counter. This type of survey was abandoned. It does not seem to warrant further study. _§_e_x 59533325333 _o_n_ 35335! M. It has been suggested . that a sex ratio might be obtained from the July brood counts by assuming equal division of the chicks as to sex, and adding those data to the counts of hens and the estimated cock popu- lation. 'He have no way of knowing whether survival of broods is similar to survival of adults from.1ate July to the hunting season, nor do we have valid data on the adult sex ratio at that time of the year, nor can we be confident that the observability of hens with broods is at all stellar to that of hens without broods. Hence, I dismissed the possibility of determining a sex ratio at this time of year from brood counts. 121 During the 1948, 1949, and 1950 hinting season, biologists and student aides interviewed hunters for bag checks, and aged several hundred cock pheasants in the bag each year. Bursa measurements, supported by the mandible test, were used (Linduska, 1945; Figure 4.1) . Although ages were recorded for several hundred birds each year, the ratios of these cocks exained is of questionable worth. Kimball (1948) found that in 'South Dakota in 1947, exmaina- tion of nearly 12,000 birds (a more than adequate sample!) resulted in a progressive shift of the youngzadult ratio from 5.0 to 1.2 over a six-week period. Allen (1941), Stokes (1954), and others have noted similar decreases in proportion of young in the cock kill as the season progresses. In the 1949 season, biologists and aides measured the bursae of about 775 cock pheasants. There was considerable overlap in the measurements, with no clear-cut distinction between adults and juveniles. I Petrides (1949) has succinctly pointed out the difficulty of obtaining rearing success from age ratios determined by examina- tion of cocks: 1) ”small" errors in aging may cause large errors in interpretation, even though misidentification of adults and young are somewhat compensating 2) extent of adult mortality must be known 3) the adult sex ratio met be known 4) s-ples must be carefully taken 8.4 122 Despite the care taken to obtain good age ratios of cocks shot, I do not consider that the ratios were reliable indicators of pheasant rearing success; spring sex ratios for the period were not reliable, the samples (areas covered) were not similar from year to year, and.there is some question about the accuracy of the examinations.1 This does not preclude the possibility that a careful sample taken each year might yield an approximate idea of relative rearing success in a poor production year compared to a good production year. As a result of my somewhat negative conclusions as to the value of our observed age ratios, Eberhardt and Slouch (1955) made a more thorough study of this shift in sex ratios by day of the season for the years 1950-1953. They also concluded that age ratim'com'parison might be _made from examination of first day age ratios where hunting effort in the areas to be compared is comparable. This will still not provide a method for converting age ratios to true rearing success. Hunter Success _ a Populatiojn Measurement Hunter success is a much misunderstood and often misused statistic. The layman is prone to use it as an index to total pheasant populations. hunter success can be a good index to 1For administrative reasons, emphasis on bag checks varied from year to year and from area to area each year. Thus, combina- tion of these unweighted samples was not practical for direct comparisons from year to year. 8.5 123 total populations, so long as it is used as a comparative figure under similar conditions, most important of which is hunting pressure. The harvestable surplus of pheasants for any given area may be taken by varying numbers of hunters (Allen, 1947), 'with inversely varying success. Thus, total kill figures for any area are likely to be more nearly an index to actual populations than the success of the hunters who harvested that total kill. During the years of this study, hunter success samples obtained from hunter bag checks were not strictly comparable as to effort expended and the location in which the samples were taken, so they are not easily comparable. A hunter success factor enters into the tabulation of hunters' report cards to determine total kill, however, (Section 2.4). In this instance, the success factor (birds shot per hunter reporting) is used legitimately, since the system assumes a comparable sample from year to year, and hunter success is not used as a statistic on its own, but rather as a step in a computation which considers total hunters as well as their success. Hunter Opinion Polls As they were checking hunters' bags, biologists asked hunters whether they had seen more, the same, or fewer pheasants than the previous year. The several thousand hunters interviewed each year responded as follows: 1946 M1 }_9_4_§ 1949 More 561 52 501 70% Same 251 802 302 161 Fewer 191 151 201 141 124 This summary of hunter opinion does not offer any apparent index to pheasant populations, although the percentage reporting 'more birds‘may indicate, very grossly, sizable increases or decreases in pheasants from year to year. Unaccountably, about the same percentage of hunters reported fewer pheasants--in good years and bad--in .pite of extremes from 5 per cent to 70 per cent reporting more birds. Surprisingly, the percentages of hunters reporting the three classifications of abundance remained relatively constant through- out the season. In 1949, for example, the percentage of hunters who reported seeing more pheasants than in the 1948 hunting season was as follows: Percentage Reporting Number of Hunters gays of Season More Pheasants Interviewed October 15 651 1 1,053 October 16 772 ' 790 October 17-23 77% 556 October 24-30 751 380 8.6 Conclusions Attempts to determine density and sex ratio indices from roadside surveys in the fall were unsuccessful. Sex ratios observed by hunters on the opening day of pheas- ant seasons were unreliable as preeeason sex ratios, due to unre- liability of hunters' observations and the removal of as much as one third of the cocks shot in the season during the one day of observation. Age ratios determined by biologists from bursa and mandible examinations were not clear-cut. Moreover, age ratios shifted 125 during the season because of differences in vulnerability of adults and juveniles to hunting. Because of this uncertainty of sex ratios and age ratios, I could not determine any indices to true productivity (rearing success). Hunter success should be used as an index to populations only when compared to hunter success indices obtained under similar conditions, especially with regard to hunting pressure. I conclude that the computed kill remains the best index to fall populations. 9.1 9.2 Chapter 9 WINTER POPULATIONS Iatroduction Changes in the habits and observability of pheasants in win- ter and spring cause extreme variation in observed pheasant sex ratios and density indices. For example, Linduska had the of- ficers record the pheasants they saw while driving during the first months of 1946 (Table 9.1). Obviously, observed sex ratio and density shifted radically. The variability continued into April (Chapter 5). It has been commonly suspected that snow cover might have an influence on observability of pheasants; and indeed, the data in Table 9.1 would support that suspicion to some de- gree--but in no particularly obvious pattern. gagriers' {gstseason Surveys Results of carriers' surveys made following the hunting sea- sons in 1946-1949 are shown in Table 9.2. On some days counts were more than double counts on other days. It was apparent that short one or two week surveys with such large daily variation could not be expected to yield accurate indices to densities or sex ratios. Examination of the data further supported the earlier sus- picion that amount of snow cover might have considerable influence on the number of pheasants observed each day. It was not practi- cal to ask the carriers to count for protractewl periods of time. 126 127 3. a .3. 2 3. n :38: nude: 395 oucuo>< in nu ma 9n a; do 908 use 235 33. new 0.» «.6 «6 no 3: “.3 838 and: Sign; awe.a Noe nno.e nnn.~ nno.m em~.~ coon neuan gasps n85: «8.8 23.8 218 333 «.3; £33 8:: eases n~-a an-o~ ne-~ m~-oe na-~ :23 :83. .3339” H.m MAQmam aquH3 NH “3”" ma: 8 . 8 6 - 84 - E m2 I 3: :5‘ 28 :5 DECEMBER - |949 JANUARY — I950 FEBRUARY MARCH Fig. 9.1--Comparison of daily average snow depth with daily pheasant observations by officers. ("Birds observed" smoothed by 3-day moving averages) 132 pointed out that the graphs in Figure 9.1 are for the purposes of inspection only, since observations are smoothed. For the statistical studies, the original data were used. No allowance was made for mortality over the winter. Any mortality that occurred would probably weaken these correlations; hence, if mortality could be considered, the correlations would probably be even better. The regression of birds seen on snow depth was calculated for the two winters. The formulas and graphs of this regression are shown in Figure 9.2. If the effect of snow depth on observability of pheasants is a constant factor from year to year, then the difference between these two lines should be due to differences in population size. In other words, if the difference between the years lies only in pheasant population densities (and not in observability), then the ratio of the numbers of pheasants seen in the two years at the same snow depths should be constant, and that constant ratio would be the ratio of the two population densities. Whether the two lines do hold the same ratio may be appraised by comparing the constant terms, the "y-intercept" (a) and the "slope" (b). The ratio of the y-intercepts is 2.22 and that of the slopes is 1.63, so it seems that the lines do not hold a constant relationship, suggesting that observability changed as snow depth increased. If snow depth has such an effect on observability of birds, quite possibly observations made only on days when there was no snow on the ground might offer a better comparison of density from one year to another. Comparing the officers' observations 133 1949-50 y = 1.803 + .676x 1948-49 y s .810 + .414x Pheasants per officer-day (y) l l l l I o 2 4 6 8 10 Average snow depth in inches (x) Fig. 9.2--Regression of pheasants observed per officer-day on daily average snow depth. 134 for only days with.no snow'cover or a trace of snow'present (Table 9.3), we find that they saw 60 per cent more birds in 1949-50 than they did in 1948-49, on days with no snow. This is not consistent with the 122 per cent increase suggested by y-inter- cepts in the regression lines in Figure 9.2. Differences in the total population would, of course, reflect differences in the cock and hen component of each year's popu- lation. Regression lines for cocks and hens separately are shown in Figures 9.3 and 9.4. To analyze this further, let us assume the model shown in Figure 9.5. If P is the observability of pheasants (or the proportion of a population seen) then we may see a certain number when there is no snow on the ground (a) and increasingly more at the rate (b) as snow depth increases. Of course, this may not be a straight line regression. It may be a curve or there may be a decided jump as soon as some snow falls, etc. This change in visibility as snow depth increases is compli- cated by the probability that observability of cocks and hens be- haves something like the model in Figure 9.6; cocks are probably always more visible than hens in winter, but the visibility of hens, with some snow cover, may increase faster than visibility of cocks. Referring back to Figure 9.5, we can say that y = pN;birds seen (y) = visibility (p) times the true population (N). using the regression formula from Figure 9.5, we can state the same thing by the formula: y = (a + bX)N 135 s2 .53 2: «an a. 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