Zambezia (1982), X (ii).ESSAY REVIEWAN IMPORTANT MILESTONE IN ZIMBABWEAN ORNITHOLOGY*THE PUBLICATION OF Irwin's book, He Birds of Zimbabwe, the result of morethan thirty years of study of Zimbabwean birds, is without doubt an important mile-stone in the development of ornithological knowledge in this country and probablymarks the end of the main period of intensive exploration of the local fauna. Thework is a direct descendant of an earlier check-list of birds from the same area(Smithers, Irwin and Paterson, 1957), but it covers a wider range of topics in a lessterse style than its predecessor. Comparison of the two publications makes itpossible to assess the progress in exploring the local fauna that has taken place inthe twenty-two years between the appearance of the check-list and the closing date(1979) for the inclusion of information in Irwin's present book. Part of this reviewwill be devoted to a consideration of progress assessed in this way.In the introduction to Ms book, Irwin states bluntly (p. 1) that it 'should not bemistaken for a field guide' and that 'there are already a number of such worksavailable which cater fully for the ordinary observer to distinguish one bird fromanother'. No specific book is suggested by Irwin but the most widely used guide tosouthern African birds, including those of Zimbabwe, is Roberto's Birds of SouthAfrica, which has appeared in four editions, respectively first published in 1940,1952,1970 and 1978 and each reprinted many times, the last three editions havingbeen edited by McLachlan and Liversidge. Since Irwin's (1981) and Roberts'sbooks will probably be used together, it is appropriate to extend the scope of thisreview to include a consideration of their relationship and suitability for joint use,Irwin's book is intended as a summary of'all that is known about the distri-bution, habitat, migration or seasonal movements, and what may be termed thegross ecology of the birds of Zimbabwe .., the particular niche that they occupy orhow they partition the environment between them in relation to their nearest rela-tives' (p. 1). Information is also provided on breeding seasons and, where morethan one subspecies of polytypic species occurs in Zimbabwe, on the charactersthat distinguish them. There are no descriptions of the bird species dealt with, noindications of inter-specific field identification characters, no details of calls, nosystematic data on kinds of food utilized, and no systematic information onbreeding behaviour other than on the host species exploited by brood parasites. Forinformation on these topics reference must be made to other works, such as that ofRoberts. Irwin's book is clearly a serious and scientifically based one, yet despitethe importance of documentation in science, only very rarely does it reference thesources of the information that it summarizes. The reason for this is that publica-tion of the book was preceded by publication of A Bibliography of the Birds ofRhodesia 1873-1978 by the same author (Irwin, 1978). The stated purpose of thisbibliography was to 'assist the serious research worker or interested layman in theretrieval of information'(p. iii). Thus Irwin's (1981) book does not really standalone but needs to be used with at least two others. It is unfortunate that thebibliography does not cover the period from 1977 (when its compilation ended) to1979 (the closing date for the 1981 book) but this omission is compensated for to*M.P.S. Irwin, The Birds of Zimbabwe (Salisbury, Quest Publishing, 1981), xvi, 464 pp.,illus., maps, Z$265.OO (special limited edition, 125 copies); ZS65.00 (special subscribers' edition,250 copies); Z$I6.00 (standard, case-bound); Z$9.0G (standard, limp).127128ESSAY REVIEWSsome extent by occasional references which appear in the text of the book, usuallyin the introductory paragraphs to each family. Regrettably these are not anywherecollected together to form a consolidated list. Clearly the relationship betweenbibliography and book is something that also needs to be considered in this review.Irwin (1981), in the introduction to his book, writes (p. 4) that the develop-ment of ornithology in Zimbabwe 'has been, and remains largely an amateur affair'and in his bibliography notes (p. vii) that 'it continues to be a preoccupation of theEuropean, whether resident or expatriate'. It has been the combination of a wide-spread network of observers constituted by interested laymen, together with themagnificent collection of more than 88,000 specimens housed in the National(Natural History) Museum at Bulawayo (in the building up of which Irwin himselfplayed a major role) that has made the present book possible. A.N.B. Masterson, inhis preface to Irwin's book, writes that he considers it important that it should'retain the dual function of building new bridgeheads on our ornithological frontierswhile, at the same time, catering for the public' (p. v); but if the general public ratherthan the knowledgeable layman is meant, then this seems impracticable in a hook ofthis type. Irwin himself has made very clear the restricted scope and objectives ofhis work and I am inclined to think that a disservice, both to him and to the public, isrendered by anything which creates the impression that the book is not aspecialized one. In this respect the title, the omission of all but a very few refer-ences, the preface, and to a large extent the garnishing of the work with colouredillustrations of a limited number of species seem ambiguous, inviting, as they do,the impression that it is a popular and comprehensive regional book like thesimilarly titled Birds of South Africa. It is true that Irwin's book has beeninfluenced by, and has much in common with, a work by Benson, Brooke, Dowsettand Irwin (1971) that is similarly titled The Birds of Zambia. but Roberts's bookantedates both of the others and this reviewer would have preferred an expansion oftheir titles so as to emphasize their more limited scope. Irwin's excellent book willnourish and broaden the interests of an already knowledgeable group of establishedlocal ornithologists but, unlike Masterson, I do not believe that it can provide 'abasis for popularizing a convenient re-introduction of all our people to the value oftheir own environmental heritage' (p. vi). It is certainly true, as Masterson says(p. vi), that 'bird life is a most accessible entity ... being present in both rural andurban areas'; but the critical task at this time in our history of awakening a genera!environmental awareness in our people, and of doing so through the study of birds(and thereby recruiting a new cohort of ornithological observers to replace thedepleted network of older ones) needs to be given entirely separate and very seriousconsideration. It does not seem to have been Irwin's aim to address these objectivesthrough his 1981 book and while the 'popularizing' features mentioned mayincrease its sales to the uninitiated, they seem unlikely to recruit any substantialnew support for ornithology.Turning to the actual bird fauna of Zimbabwe, it is worthwhile noticing firstthat about 1,850 species have been recorded in and around the continent of Africataken as a whole (Brown, Urban and Newman, 1982). Table I summarizes thenumber of species listed in the 1957 check-list, in Irwin's (1981) book, and in thelatest (1978) edition of Roberts. It can be seen that Irwin (1978) considers that635 species of bird have been acceptably recorded from Zimbabwe, that is, slightlyover 34 per cent of the total known from the continent and 75 per cent of the totalconsidered by McLachlan and Liversidge (1978) to be acceptably recorded fromC.B. COTTRELL129Table INUMBERS OF BIRD SPECIES IN ZIMBABWEAND SOUTHERN AFRICARegionCoveredZimbabweZimbabweSouthern Africa tAlreadyAcceptablyRecorded565635*845May BecomeAcceptablyRecorded1940*231SourceandDateSmlthereefaf. (1957)Irwin(1981)McLachlan andLiversidge (1978)* Represents the increase in knowledge over a twenty-two-year period,t Represents the approximate size of the avifauna of the southern African subcontinent,t This figure is derived from a consideration of the list of 37 'doubtful species' given onpp. xxxi-xxxii of this source.southern Africa. This figure is all the more remarkable when it is realized thatZimbabwe's land-locked position automatically excludes some ten families of sea-associated birds found along the southern African coasts as well as many species oftwo other such families: moreover Zimbabwe lacks not only any real arid areas(comparable to those of Somalia and Namibia) but also any extensive system ofsaline pans, both of these habitats having characteristic bird faunas.Table I also indicates the surprising fact that in the twenty-two years since thepublication of the check-list of Zimbabwean birds in 1957, there has been a netincrease of some 70 acceptably recorded bird species (a i 2 per cent increase on theearlier figure). The actual situation is that 72 such additional species ha¥e beenrecorded, while two of the original supposed species have been lost by beingcombined together as subspecies of single polytypic species. While it is true that thefigures from the three sources are not precisely comparable since their authors haveused slightly different criteria for acceptable records, discrepancies from thissource are not large. McLachlan and Liversidge (1978) write (p. xi) that 'obviouslyevery aviary escapee or storm-driven bird cannot be included' and have adopted asa guide-line for the future the admission of a species 'on the basis of five specimensexcept for birds which occur just across the border when fewer are acceptable',Smithers et al. (1957) based the admission of species to their check-list firmly onthe existence of museum material collected within the country, but Irwin (1981)has relaxed this somewhat; and, although he says (p. 3) that 'ideally a specimencollected within the geographical limits of Zimbabwe should be available*, liebelieves (p.3) that "such requirements are no longer considered absolutely neces-sary and records based on photographs, birds trapped for ringing or otherwise well-documented occurrences are considered sufficient for inclusion*. Where Smitherset al. (1957) considered that sufficient grounds existed for believing that a speciesdid occur in Zimbabwe even though no specimen existed,- they included suchspecies as unnumbered italicized entries pending farther proof. There were 17 suchentries in their list, Irwin (1981) likewise includes, as unnumbered entries, placedwithin square brackets, some 40 species believed likely to be acceptably recorded130ESSAY REVIEWSin Zimbabwe in the future. McLachlan and Liversidge (1981) give a list of 37'doubtful species* some of which relate to southern African records that havedefinitely been rejected. The figure of 27 given in Table I is therefore derived by thisreviewer by extracting only those entries that appear to him to be comparable tothose given in the 'possible' category in the other two works.In considering the advances made in Zimbabwean ornithology during the lasttwenty-two years, it is instructive to examine the fate of the 19 possible speciesgiven by Sraithers et al (1957). All but 3 have in fact been admitted by Irwin (Nos18,38,63,93,116,130,171,177,178,184,198,199, 209,258, 373 and 580);2, the Blue Crane (Anthropoid.es paradisea) and Burchell's Glossy Starling{Lamprotornis australis), remain as possibles while the last, the Pink-throatedTwinspot (Hypargos margaritaius), has either been rejected or may perhaps havebeen overlooked since it is mentioned in neither Irwin (1978) nor Irwin (1981),although the stated grounds for considering that it may eventually be found inZimbabwe would appear to be as valid now as they were in 1957.A comparison of the entries for 1957 with those of 1981 for the first threespecies on the 'possible' list of Smithers etal (1957) is fascinating in its revelationof the changes, not only in our knowledge but also in the actual status, in Zimbabwein recent years, of the species concerned:Egretta vinaceigula Slaty Egret.1957: This doubtful species, probably a colour phase of M. (sic)ardesaica has been taken at Kabuta, Caprivi Strip, adjacent to the .,.border and may therefore be expected in swampy areas in the west andnorth-west (p, 25).1981: Favours the periphery of shallow expanses of receding waterwith a good growth of stranded aquatic vegetation, moving away whenthe level rises. In Botswana, where it is now relatively well-known, it isbelieved to undergo movements outside the breeding season, returningin mid-summer. Such a dispersal would accord with two sight records, inthe same season, probably of the same bird from Rainham Dam... andfrom Lake Mcllwaine... Another was seen on a number of occasions onthe flood plain of the Zambezi River at Kazungula... Confusion in thepast with the Black Egret E. ardesaica may be partly responsible for thepoor documentation of this species' status, but it must remain the rarestof all the African herons (p. 34).Plegadis falcinellus Glossy Ibis.1957: Occurs in the Zambezi Valley at Kabuta, Caprivi Strip adjacentto the .. . border and undoubtedly, therefore, will in time be shown tooccur in the north-western area. Seen on a dam near Salisbury and atSelukwe and Bindura (p. 29).1981: On edges of pans and dams, feeding in the shallows. It appearsonce to have been a scarce or irregular vagrant, but in the last decades itsoccurrences have become increasingly frequent and it can now be seenregularly in flocks of a dozen or more, some remaining over an extendedperiod... All must come from beyond our borders, probably from SouthAfrica, although there seems no reason why it should not breed as it doesso in neighbouring countries (p. 44).C.B. COTTRELL131Neophron percnopterus Egyptian Vulture.1957: No material Is so far available from the Territory but It may beexpected to occur as it has been recorded to the south (p. 35).1981: Was originally found on the open, Mghveid grasslands of SouthAfrica . . . Once widespread, it has since declined to virtual extinctionthroughout the sub-continent, the last known breeding record from theTranskei more than half a century ago . . , unlikely ever to have beencommon in Zimbabwe .,. there are only three records in the post-1945period which may be acceptable . . . (pp, 57-8).These examples make it clear that if 16 ofthe 19 'educated guesses' aboutprobably-occurring species made by Smithers et ah (1957) have now become'acceptable records', these changes in status have not been brought about merely asthe result of a relaxation of criteria for acceptability by Irwin (1981) but rather asthe result of a real increase in knowledge, sometimes accompanied by changes Inrange and commonness of occurrence ofthe bird concerned.It is surprising how much there remained to be learnt in 1957 not only aboutthe occurrence of particular bird species (and subspecies) within Zimbabwe butalso of their taxonomy. Ofthe total of 72 additional species that Irwin considers tohave become acceptably recorded in Zimbabwe between 1957 and 1981, at least34 breed, or probably breed, in the country and are not, therefore, mere migrants thatmay pass through or reach the area on more or less rare occasions. Some ofthemost interesting of these are the appearance and breeding or possible breeding ofthe Great Crested and Black-necked Grebes (Podiceps cristatus mdP, nigricollis)on artificial impoundments in Matabeleland; the breeding of the Red-tailedFlufftail (Sarothrura affinis) in the eastern-border mountains, of the Bronze-naped Pigeon (Columba delegorguei) in the Makurapini Valley; of the possiblebreeding ofthe Barred Long-tailed Cuckoo (Cercococcyx montanus) in the Vimbaforest; of the Cape Eagle Owl (Bubo capensis) on the eastern-border mountainsand in the Matopos; ofthe Cliff Swallow (Hirundo spilodera) near Bembezi; and ofthe Bokmakerie (Telophorus zeylonicus) in the Chimanimani Mountains. Onlyone ofthe newly recorded species, the pelagic Sooty Tem (Sterna fuscata) arisesas the result of being driven inland in numbers on several occasions, by tropicalcyclones, from the Mozambique coast. One of the breeding species, the HouseSparrow (Passer domesticus), has colonized the country from expanding popula-tions of Palaearctic taxa introduced originally at Durban and Cape Town,appearing first in Zimbabwe in the mid-1950s and completing its now widespreadbut patchy occupation in association with man, within a decade. Four ofthe newlylisted species have appeared as the resultof reassessment of the taxonomic status ofsubspecies or groups of subspecies that were grouped together, in 1957, as singlespecies. The African Hobby (Falco cuvieri) which breeds in Zimbabwe, has beenseparated, at the species level, from the migrant European Hobby (Falcosubbuteo); the African Cuckoo (Cucularis gularis), which also breeds inZimbabwe, has been separated from the migrant European Cuckoo (C. canorus);the Acacia Grey Tit (Parus afer) and the Miombo Grey Tit (P. griseiventris), bothof which breed in Zimbabwe, have been recognized as distinct species; theChirinda Apalis (Apalis chirindensis) has been separated from the Black-headedApalis (A. melanocephala) as a distinct species that also certainly breeds inZimbabwe, In contrast, two species-rank taxa from the 1957 list have been132ESSAY REVIEWSremoved from the 1981 list as the result of being combined with their nearestrelatives. These are Delagorgue's Green Pigeon which has now been grouped as asubspecies of the African Green Pigeon (Treron australis); and the Grey-backedGlass-eye, now combined with the Green-backed Glass-eye under the Englishname of Bleating Bush Warbler {Catnaroptera brachyura).A new Zimbabwean species record arises from the simultaneous recognitionof the African Marsh Harrier (Circus ranivorus), which breeds locally, as aspecies distinct from the European Marsh Harrier (C. aeruginosus) and theacceptance of some local sight records of the latter from Zimbabwe, althoughMcLachlan and Liversidge (1978) regard these as doubtful.A number of taxa formerly regarded as subspecies of polytypic species havebecome elevated to full species rank but, because the species to which they wereoriginally assigned have not been recorded in Zimbabwe, these changes do notaffect the total number in the list of records. These include the Augur Buzzard(Buteo augur) formerly considered a subspecies of the South African JackalBuzzard (B. rufofuscus); the Black-breasted Snake Eagle {Circaetus pectoralis)formerly considered a subspecies of the European Short-toed Eagle {Circaetusgallicus) (neither of which changes are accepted by Brown, Urban and Newman,1982); and the Miombo Double-collared Sunbird (Nectarinia manoensis) whichhas often been listed, in the recent past, as a subspecies of the South African LesserDouble-collared Sunbird (N. chalybea). This last taxon has had a very chequeredhistory in the popular southern African ornithological literature. This history isworth outlining because it illustrates some of the difficulties faced by the amateur inusing this literature. For a full appreciation of the situation, however, Clancey andIrwin's (1978) paper must be consulted, Roberts (1940) originally gave it fullspecies rank (No. 759) as the Rhodesian Double-collared Sunbird (N. brachiatus);subsequently, McLachlan and Liversidge (1952) listed brachiatus as a subspeciesof iV. chalybea (No. 760(b)), as did Smithers et ah (1957). Later this populationwas referred to as N. chalybea manoensis (McLachlan and Liversidge, 1970,1978; Mackworth-Praed and Grant, 1963; Benson et ah, 1971). Now, following areview by Clancey and Irwin (1978), it has again been accorded full species rank.Only the acquisition of much more detailed knowledge of the various populationswill allow a full assessment of the extent to which the new taxonomic arrangementreflects biological reality. Records formerly attributed to the Black-winged Plover(Stephanibyx melanopterus) are now attributed to the Lesser Black-winged Plover(Vanellus lugubris). Only one of the new species added to the Zimbabwean list,the Lemon-breasted Canary (Serinus citrinipectus) has been described since thepublication (1960) of the check list. A second such recently described species, thesomewhat controversial Brown Firefinch Indigobird (Vidua incognita), is listed aspossible in Zimbabwe.Enough detail has been given to show that while the period 1957-81 has notbeen marked by the recognition of many previously undescribed species insouthern Africa, the new features of Irwin's book reflect large advances inknowledge of the extent of the Zimbabwean fauna over this period and not simplychanging views about the taxonomic rank to be accorded to local populations,though these too are taken into account. Changes in knowledge of the extent of theZimbabwean fauna are not likely to be so marked in the future, but that they willcontinue to occur is testified by the recent recording, on the basis of a collectedspecimen, of the Short-tailed Pipit (Anthus brachyura) at Beit Bridge (Donnelly,v-C.B. COTTRELL1331982), a species that was not even included as a possible record by Irwin (1981).Neverthless the main advances in the future will be in increased knowledge of thebiology (in its widest possible sense) of species already recorded and in thedetection and recording of the changes in their status that will inevitablyaccompany the development of Zimbabwe. For these tasks Irwin's (1981) book,his (1978) bibliography and one of the available field guides (here assumed, on thegrounds of preponderance of use, to be McLachlan and Liversidge, 1978) mustform the background. This being so, how do these books relate to one another andhow conveniently can they be used together for information retrieval?Scientific biological classifications, through their hierarchichal arrangementof successively more inclusive taxa (e.g. species, genera and families), are intendedto facilitate information retrieval by grouping together, in more inclusive taxa,those subordinate taxa that are considered to be related in an evolutionary sense.Unfortunately, since the evolutionary relationships of even the best known groupsof animals have not, as yet, been adequately investigated, changes in classificationsintended to improve them are likely to continue to appear for a long time to come.The taxa that are classified need individual labels and are therefore namedaccording to a set of rules laid down in the International Code of ZoologicalNomenclature (1964). These rales are intended to promote the stability anduniversality of the names of animal taxa and also to ensure that each such name isdistinct and unique. However, we live in a period of continuing nomenclatorialchange: firstly because the provisions of the Code have been widely applied only inrelatively recent times, so that much research into the validity of currently appliednames remains to be done; and secondly because the Code is designed specificallyso as not to impede freedom of taxonomic (i.e., classificatory) judgement andaction, and some kinds of classificatory changes automatically affect the combina-tions formed by generic and specific epithets in the names of species. At this time itis still very unlikely that two publications on southern African birds will employidentical nomenclature and classification. Indeed such closely related works asIrwin's (1978) bibliography and his (1981) book differ as the result of changes inboth the generic and specific epithets of 2 species, of changes in the generic epithetsof 14 species and of changes in the specific epithets of 8 species. Even thesequential numbers assigned to the species listed as acceptably recorded in the twoworks do not correspond over considerable sections. The differences betweenMcLachlan and Liversidge (1978) and Irwin's works are far greater: the familiesrecognized are not identical; a number of genera are actually placed in differentfamilies (e.g. Nicator in LANIIDAE (Shrikes) instead of PYCNOTIDAE (Bulbuls);Pinarornis iniiMALiDAE (Babblers) instead of TURDIDAE (Thrushes and Robins);Porisoma, Hyliota, Chloropeta, Seicercus and Stenostira in MUSCICAPIDAE(Flycatchers) instead of SYLVIIDAE (Warblers)); scientific names and commonnames may be very different and, of course, there is no correspondence between theserial numbers. With a little experience an interested layman quickly learns tobridge such difficulties but much time can be saved in establishing identities, if ashas been done in Irwin's (1978) bibliography, a cross-reference (usually to theserial number where one exists) is given to treatments of the same taxon in otherstandard works. It is much to be regretted that this practice has not been followed inIrwin (1981).The successive editions of Roberts's work have not kept fully abreast with134ESSAY REVIEWScurrent taxonomic practice and nomenclature, but since Clancey (1980) has editeda new check-list of southern African birds, the scientific names of which have beenadopted for use in Ostrich (the Journal of the South African OrnithologicalSociety), and since this list also forms the basis of Irwin's (1981) book, it is to beexpected that the next revision of Roberts's work will show a much greatercorrespondence with Irwin's (1981) one. The coloured figures in McLachlan andLiversidge (1978) cover almost all of the species dealt with by Irwin although therelevant Zimbabwean subspecies are not always the ones illustrated. Only four ofthe species acceptably recorded for Zimbabwe are not illustrated in this latestedition of Roberts. These are the Lesser Cuckoo (Cuculus poliocephalus), theRed-ramped Swallow {Hirundo daurica), the Golden Pipit (Tmetothylacustenellus) and the Miombo Sunbird (Nectarinia manoensis). Useful figures of thefirst and third are, however, given in Irwin (1981). The Miombo Sunbird wasfigured (as No. 759) in the three earlier editions of Roberts but has been eliminatedfrom the re-arranged and revised plates of the fourth edition. If useful additions tobiological knowledge of the Miombo, Lesser and Greater Double-collaredSunbirds (N. manoensis, N. chalybea and N. afer) are to be made by laymen, thenwidely available figures showing the differences between them, as does the plate inClancey and Irwin (1978) for males, together with notes on field marks, areessential. This of course applies to other difficult species which, because ofidentification problems, are neglected by field-workers.Irwin's (1981) book begins with a brief but useful introduction setting out itsobjectives, constraints and background and describing the land surface and climateof Zimbabwe and its vegetation as seen from an ornithological point of view. Thekinds of vegetation recognized are illustrated by 22 black and white photographs byPeter Steyn but unfortunately these have not reproduced well, those of the InyangaDowns, Pungwe Gorge and Chimanimani Mountains being particularly poorlyprinted and probably quite useless for conveying to anyone who has not visitedthese places the nature of the vegetation existing there. The book closes with agazeteer of localities and is furnished with indices to scientific and English names.There are 25 coloured plates, including the frontispiece, and these fall into twocategories: 13 are full-plate paintings of favourite single species in their naturalhabitats (Taita Falcons, Helmeted Guinea Fowl, Rock Pratincole, NarinaTrogon, Red-billed Wood Hoopoe, Silvery-cheeked Hornbill, African Pitta,Heuglin's Robin, Boulder Chat, Paradise Flycatcher, Scarlet-chested Sunbird,Red-headed Weaver and Red Bishop), while 12 are composite plates covering anumber of species in more conventional field-guide style. The original paintings byPeter Fogarty were clearly very fine indeed but some have unfortunately sufferedconsiderably in the process of reproduction. A number show a tendency to anoverall dull bluishness which detracts badly from the rich brown colourations inmany representations. This defect is variable in different copies of the book, someexamples of some plates being far worse than others. In many cases, especially inthe composite plates, the paintings have been reproduced on slightly too large ascale so that the tail-ends and beak-tips of the birds represented have been lost atthe page edges. Almost all the bird species shown are figured in Roberts and onstrictly utilitarian grounds most could therefore have been dispensed with but, asalready noted, there are useful figures of the Lesser Cuckoo and Golden Pipit aswell as figures of the females of the Bronze-naped Pigeon and the LesserSeedcracker (Pyrenestes minor) and of two subspecies of Green Pigeon whichC.B. COTTRELL135complement those in Roberts, The figures of the natural hybrids between species offrancolin are of extraordinary interest and the plate illustrating immatureplummages in certain species is very useftil; both convey information not readilyavailable in field-guides.The distribution maps are dear and serve to illustrate some of the kinds ofpattern seen in Zimbabwean birds as well as areas of sympatry, allopatry orparapatry in related species, these being of particular interest in the cases of thepairs of hybridizing francolin species (Fracolinus natalensis and F. odspersus;F. swainsonii andF, afer). Perhaps in some cases the maps could have been moreimaginatively used to illustrate the correlation between actual records and keyfactors that may be hypothesized as determining distributions, for instance byincluding selected contours or the boundaries of particular vegetation types. Twokinds of time-related distribution maps might have been of interest: one in which thesymbols are varied to indicate the season of the record and one in which they arevaried to show the historical period of the record, for instance pre-1920,1920^45, and post-1945.The real merit of the book lies, of course, in the 403 pages that constitute theSystematic List, This is well produced with only very few typographical or othererrors, (The common name of Haliaeetus vocifer appears as the 'African EagleFish',) The authors and dates of publication of specific epithets are much moreaccurately cited than in Roberts. In a few instances they have been enclosed inbrackets when the specific epithet seems not to have been originally published in adifferent combination, which such enclosure is intended to show (e.g. Anashottentota). There is also a curious and slightly contusing use of brackets to encloseonly the date of publication of subspecific epithets that were not originallypublished in different combinations: it would surely have been better merely tohave separated the author's name from the unbracketed date by a comma asrecommended in the Code. In certain places, especially in the introduction, there isa tendency to make use of the words 'race' and 'form', the former apparently as analternative to subspecies and the latter as a term covering taxa of both specific andinfraspecific rank. Neither has any status in the Code and both may have quitedifferent connotations in the literature of other animal groups. The dropping ofboth of these imprecise terms is long overdue in serious ornithological writing.In summarizing all that is currently known in relation to the birds ofZimbabwe in the areas of Ms chosen topics, Irwin has, in effect, set out ordeveloped innumerable current hypotheses about the taxonomic status, distribution,habitat preferences (seen in terms of altitude and vegetation), long-distancemigrations, short-distance seasonal movements, niche limits and breeding seasonsof populations of Zimbabwean birds. These hypotheses are now available fortesting, by attempted falsification, through surveys or experiments according to theusual procedures for advancing and refining scientific knowledge. The book is agoldmine for any Zimbabwean interested in birds and who is seeking a researchproject at any level of complexity. To give a very few examples:Ringing returns suggest that Southern African populations of the White-breasted Cormorant (Phalacrocorax carbo) of inland waters may havelittle or no direct contact with the populations of the species (not evenrecognized as a different subspecies) breeding along the coasts. In what136ESSAY REVIEWSphysiological, behavioural and ecological adaptations do these popula-tions differ? Is it possible that we are dealing with unrecognized siblingspecies?Why has the Reed Cormorant (Phalacrocorax africanus) respondedmore dramatically, by increase in population, to the creation of LakeKariba and other dams than has the White-breasted Cormorant, otherthan on the 'highly eutrophic Lake Mcllwaine', where the reverse hasbeen the case ? What effect have recent measures to reduce nutrient flowinto Lake Mcllwaine had on this situation?Can it really be true that Darters {Anhinga melanogaster), whilefeeding in the same areas and on the same fish species as the ReedCormorant {Phalacrocorax africanus) avoid competition through theemployment of different feeding and capture techniques? If so, whatpredator-prey population characteristics are involved?What factors determine the fact that the Black-bellied Sunbird (Nectar-ina shelleyi) occurs in Brachystegia woodland in Zambia but not inZimbabwe?Why do the Yellow-bellied Sunbird (N, venusta) and the White-belliedSunbird {N. talatala) appear to co-exist without obvious ecologicaldifferences in the middle Zambezi Valley but remain segregatedelsewhere? If this can be confirmed, is the ability to co-exist in theZambezi Valley causally related to the unusually diminutive bill-size ofthe Yellow-bellied Sunbirds in this area?The approximately thirty-year seeding ('masting') cycle of the BinduraBamboo (Oxytenanthera abyssinica) is commonly thought to be adevice to avoid seed-predation, yet the Pied Mannikin (Spermestesfringitloides) has evidently become very closely associated with thisplant, whose seeds are believed to be its preferred food. What effect doesthe availability, or otherwise, of bamboo seed have on the populationdynamics and behaviour of the Mannikin?Enough detail has been given to illustrate the extraordinary interest of thisbook for anyone with an enquiring mind and it is appropriate to turn finally to theimportance of the book as a background to the urgent task of safeguardingZimbabwe's fascinating bird fauna. Irwin deals with a considerable number ofcases where the population levels of certain water birds have been favourablyaffected by the creation of artificial impoundments (e.g., certain cormorants andherons). He makes it clear in his introduction (p. 12), however, that there arewidespread negative effects; 'great inroads have been made in the woodedsavannahs in this century , . , large areas , , . have been cleared of their originalwoody vegetation or severely degraded.., Overstocking has denuded large areas ofgrass cover .., Clearly if this book has a successor, there will be a very differentstory to tell'. Despite this, the Systematic List gives surprisingly little indication ofthe effects of these negative influences and the question arises as to whether thecurrent methods, recording practices and indeed the overall orientation ofZimbabwean ornithologists are really suitable to monitor and detect such changes.It is always exciting to record the addition of a new, previously unrecorded speciesto an area list, but much less exciting, and indeed much more difficult, to establishC.B. COTTRELL137that one is absent from a habitat in which it was previously known to occur. This iswhere a system of regular biological recording involving distribution maps withperiod-specific record symbols might help to provide an early warning. No speciesof bird on the continent of Africa as a whole is yet known to have become extinctbut, as the quotation on the Egyptian Vulture given earlier indicates, the time is notfar off when this will occur. The next period of ornithology must rapidly developrecording methods that will signal the decline of what may, at present, seem to beubiquitous birds in Zimbabwe.In conclusion, Irwin's book, despite its restricted objectives,, is an exceptionallyvaluable publication which anyone interested in birds in this country needs readyaccess to in order to supplement information in existing field guides. Its standardhard cover and soft cover editions are reasonably priced and, in view of the wealthof information and ideas that it contains, it is well worth purchasing.University of ZimbabweC.B, COTTRELLReferencesBENSON, C.W., BROOKE, R.K., DOWSETT, R.J. and IRWIN, M.P.S. 1971 TheBirds of Zambia (London, Collins).BROWN, L.H., URBAN, E.K., NEWMAN, K. 1982 The Birds of Africa, Volume I(London, Academic Press, to be completed in 3 further volumes),CLANCEY, P.A. (ed.) 1980 SAOS Checklist of Southern African Birds(Johannesburg, South African Ornithological Society).CLANCEY, P. A. and IRWIN, M.P.S. 1978 'Species limits intheNectarinia afer/N.chalybea complex of African Double-collared Sunbirds', Durban MuseumNovitates, XI, 331-51.DONNELLY, B.G. 1982 'First record of the Short-tailed Pipit in. Zimbabwe',The Honey guide, CX, 45.IRWIN, M.P.S. 1978 A Bibliography of the Birds of Rhodesia, 1873-1978(Salisbury, Rhodesian Ornithological Society).IRWIN, M.P.S. 1981 The Birds of Zimbabwe (Salisbury, Quest Publishing).MCLACHLAN, G.R. and LIVERSIDGE, R. (revisers) 1952, 1970 and 1978Roberts' Birds of South Africa (Cape Town, Trustees of the John VoelckerBird Book Fund).ROBERTS, A. 1940 The Birds of South Africa (London, Trustees of the SouthAfrican Bird Book Fund).SMITHERS, R.H.N., IRWIN, M.P.S. and PATERSON, M.L. 1957 A Check List ofthe Birds of Southern Rhodesia (Cambridge, Rhodesian OrnithologicalSociety).