SPECIAL REVIEW Bird Numbers in Finland: A Bold Effort towards Estimating a Nation's Avifauna*

Transcription

1 SPECIAL REVIEW Bird Numbers in Finland: A Bold Effort towards Estimating a Nation's Avifauna* By E. M. NICHOLSON AMONG THE MANY generous and thoughtful acts of our hosts in Finland at the Xllth International Ornithological Congress was the timely production and presentation to each member of this 181-page survey in English of the bird population of Finland. Illustrated by 131 maps of the distribution of individual species and forming a revised and rewritten version of the same author's Suomen lintujen levinneisyys ja lukumaara (published in Finnish 1955), it differs from most works of its kind in not stopping at listing the individual occurrences of rarities and the general distribution and frequency of the commoner species. It aims instead, with characteristic Finnish indifference to seemingly insurmountable obstacles, at providing nothing less than a summary of the actual numbers and regional density patterns of all the regular breeding species in Finland. It opens a window on to a rich and interesting avifauna which difficulties of language and travel have hitherto kept beyond the range of most British ornithologists, even though Finnish ornithology was partly pioneered by such Englishmen as Wolley, who just over a century ago first discovered there the nest of the Smew (Mergus albellus). Arranged in a Wetmore order it deals with 327 species, although these include some which have occurred only as escapes such as the Black Swan (Cygnus atratus), Bar-headed Goose (Anser indicus), Canada Goose (Branta canadensis) and Demoiselle Crane (Anthropoides virgo) and one or two, surprisingly including the Great Northern Diver [Gavia immer), which are given space only to point out that no acceptable record yet exists for them in Finland. The maps (which are provided for most but by no means all species reaching any appreciable density in any part of Finland) are elaborately prepared to convey changing status and to grade their supporting data as FINNISH BIRDS: THEIR DISTRIBUTION AND NUMBERS. By EINARI MERIKALLIO. Fauna Fennica V in series of publications by Societas pro Fauna et Flora Fennica. (Tilgmann, Helsinki, 1958). 181 pages; 131 maps. No price given. continued... 22

2 VOL. LII] SPECIAL REVIEW: FINNISH BIRDS 23 well as to indicate density according to a frequency scale drawn up with the help of Professor O. Kalela. This distinguishes nine different frequency levels ranging from below 0.05 pairs per square kilometre ("very scarce") to above 25 pairs ("extremely numerous") in each of ten zoological regions. The necessary data are derived largely from sample transect counts along survey lines arranged in squares 4 kms. in perimeter with a width of some 50 metres for the main belt. A much broader "auditory belt" covering nearly seven times as wide a band is used for the more infrequent species. In this way transects aggregating 1,092 kms. were covered, scattered throughout Finland, and giving records of 67,321 individuals belonging to 130 species. Most bird census work in other European countries has hitherto been based on particular conspicuous species, and few experienced counters have been willing to contemplate even on a sample basis the estimating of a national population as a whole, although certain informed guesses have been hazarded. Finnish ornithologists believe that, despite the formidable obstacles, a worthwhile degree of accuracy is attainable. Dr. Merikallio, however, is careful to point out that certain species (owing to their inconspicuousness, gregariousness, or other factors) cannot be reliably sampled by such methods and he indicates that a number of his estimates must for such reasons be considered as probably too high, too low, or simply too uncertain. Although it must be emphasized that the book itself contains no summary census table, it gives all the necessary data for compiling the following one: TABLE I ESTIMATED POPULATIONS OF BIRDS BREEDING IN FINLAND * = Rough estimate. t = Uncertain or suspect estimate. + = Estimate incomplete or prior to recent increase. = Estimate probably too high or prior to recent decrease. The ten commonest species are numbered in order on the left. It appears that every regular breeding species is included, except a few whose status is still uncertain Water Rail (Rallus aquaticus), Moorhen (Gallinula chloropus) and Terek Sandpiper (Tringa terek) and certain others for which firm data are lacking Smew (Mergus albellus), Snowy Owl (Nyctea scandiaca) and Greyheaded Woodpecker (Picus canus). Black-throated Diver (Gavia arctica) Red-throated Diver (Gavia stellata) Great Crested Grebe (Podiceps cristatus) Red-necked Grebe (Podiceps griseigena) Slavonian Grebe (Podiceps auritus) Heron (Ardea cinerea) Bittern (Botaurus stellaris)... Mallard (Anas platyrhynchos) Teal (Anas crecca) 5.ooo 3, ,000 80, ( ) (*)

3 24 BRITISH BIRDS [VOL. LII Garganey (Anas querquedula) Wigeon (Anas penelope) Pintail (Anas acuta) Shoveler (Spatula clypeata) Scaup (Aythya mania) Tufted Duck (Aythya fuligula) Pochard (Aythya ferina) Goldeneye (Bucephala clangula) Long-tailed Duck (Clangula hyemalis)... Velvet Scoter (Melanitta fusca) Common Scoter (Melanitta nigra) Eider (Somateria mollissima) Red-breasted Merganser (Mergus senator) Goosander (Mergus merganser) Grey Lag Goose (Anser anser) Lesser White-fronted Goose (Anser erythropus) Bean Goose (Anser arvensis) Whooper Swan (Cygnus cygnus) Golden Eagle (Aquila chrysaetos) Buzzard (Buteo buteo) Rough-legged Buzzard (Buteo lagopus)... Sparrowhawk (Accipiter nisus) Goshawk (Accipiter gentilis) Black Kite (Milvus migrans)... White-tailed Eagle (Haliaetus albicilla)... Honey Buzzard (Pernis apivorus) Marsh Harrier (Circus aeruginosas) Hen Harrier (Circus cyaneus) Osprey (Pandion haliaetus)... Hobby (Falco subbuteo) Peregrine (Falco peregrinus) Gyr Falcon (Falco rusticolus) Merlin (Falco columbarius) Kestrel (Falco tinnunculus) Willow Grouse (Lagopus lagopus) Ptarmigan (Lagopus mutus)... Black Grouse (Lyrurus tetrix) Capercaillie (Tetrao urogallus) Hazel Hen (Tetrastes bonasia) Partridge (Perdix perdix) Quail (Cotumix coturnix) Pheasant (Phasianus colchicus) Crane (Megalornis grus) Spotted Crake (Porsana porzana) Corncrake (Crex crex) Coot (Fulica afro) Oystercatcher (Haematopus ostralegus) Lapwing (Vanellus vanellus) Ringed Plover (Charadrius hiaticula) Little Ringed Plover (Charadrius dubius)... Golden Plover (Charadrius apricarius) Dotterel (Charadrius morinellus)... Turnstone (Arenaria interpres) Snipe (Capella gallinago) Great Snipe (Capella media)... Jack Snipe (Lymnocryptes minimus) Woodcock (Scolopax rusticola) 1,000- (*) 40,000 (*) 20,000 (*) 4,000 (*) 1,000 40,000 (*) 5,000 (*) 50,000 (*) 500 (*) 5,000-8,000 ( + ) 500 (*) 25,000 10,000 4, ( + ) 200 (*) 1,000 >S (+) 82 2,300 3,000 ( ) 1,200 (+) 500 (+) ,000 (+) 600 (t) 500 (t) 2,700 (t ) 500 (t) io( + ) 1,600 (+) 3,400 (+) 110,000 4, , ,000 ( ) 228,000 15, ,000 ( ) (1938 est.) 8,500.. "several hundred" 900 (-) , (+) 1,000 (*) T 8,000-9,000 ( ) 1,500-1,600 90,000 5 II.OOO l6,0oo (f)

4 VOL. LH] SPECIAL REVIEW: FINNISH BIRDS 25 Curlew (Numenius arquata)... 44,000 Whimbrel (Numenius phaeopus) 43,000 Bar-tailed Godwit (Limosa lapponica) 0-20 Green Sandpiper (Tringa ochropus) 2 Wood Sandpiper (Tringa glareola) Common Sandpiper (Tringa hypnleucos) ,000 10,000 (+) Redshank (Tringa totanus) Spotted Redshank (Tringa erythropus)... 24,000 Greenshank (Tringa nebularia) 30,000 Temminck's Stint (Calidris temminckii)... (*) Dunlin (Calidris alpina) 3 Broad-billed Sandpiper (Limicola falcinellus) 11,000 Ruff (Philomachus pugnax) 7.S Red-necked Phalarope (Phalaropus lobatus) 700 Arctic Skua (Stercorarius parasiticus) 130 Long-tailed Skua (Stercorarius longicaudus) 1,5 (+ -) Great Black-backed Gull (Larus marinus) 600 Lesser Black-backed Gull (Larus fuscus)... 4,000 Herring Gull (Larus argentatus) 2,300-3,000 (*) Common Gull (Larus canus) S.000 Little Gull (Larus minutus) Black-headed Gull (Larus ridibundu.s) 20,000-30,000 Caspian Tern (Hydroprogne caspia) 700 Common Tern (Sterna hirundo) Arctic Tern (Sterna macrura) Razorbill (Alca tor da) Black Guillemot (Uria grylle) 6,000 6, ,000 (*) 1,500 Stock Dove (Columba oenas) 8,000 Rock Dove (Columba livia)... Woodpigeon (Columba palumbus)... 50,000 (t) 164,000 Cuckoo (Cuculus canorus) 30,000 Eagle Owl (Bubo bubo) Hawk Owl (Surnia ulula) 200 3,600 (t) Pygmy Owl (Glaucidium passerinum) Tawny Owl (Strix aluco) Great Grey Owl (Strix nebulo.sa) 50- (*) Ural Owl (Strix uralensis) (+) Long-eared Owl (Asio otus) 2,500 (t) Short-eared Owl (Asio flammeus) 9,000 (+ ) Tengmalm's Owl (Aegolius junereus) 1,500 Nightjar (Caprimulgus europaeus) 4-3 Swift (Apus apus) 25,000 Kingfisher (Alcedo atthis) Great Spotted Woodpecker (Dendrocopos ma jot ) White-backed Woodpecker (Dendrocopos leucoto. ) 4,000 (tt ) Lesser Spotted Woodpecker (Dendrocopos minoi Three-toed Woodpecker (Picoides tridactylus). Black Woodpecker (Dryocopus martin*)... Wryneck (Jynx torquilla) Woodlark (Lullula arborea) Skylark (Alauda arvensis) Shore Lark (Eremophila alpestris) Swallow (Hirundo rustica)... House Martin (Delichon urbica) Sand Martin (Riparia riparia) Golden Oriole (Oriolus oriolus) Raven (Corvus corax) ) 3,000 (+ +) 23,000 15,000 19, ,000 10, , ,000 (t) 300,000 (tt ) 1,800 7,800

5 26 BRITISH BIRDS [VOL. LII Hooded Crow (Corvus cor one comix) Rook (Corvus frugilegus) Jackdaw (Corvus monedula)... Magpie (Pica pica) Nutcracker (Nucifraga caryocatactes) Jay (Garrulus glandarius) Siberian Jay (Perisoreus infaustus) Great Tit (Parus major) Blue Tit (Parus caeruleus) Coal Tit (Parus ater) Crested Tit (Parus cristatus) Siberian Tit (Parus cinctus)... 4 Willow Tit (Parus atricapillus) Long-tailed Tit (Aegithalos caudatus) Treecreeper (Certhia familiaris) Wren (Troglodytes troglodytes) Dipper (Cinclus cinclus) Mistle Thrush (Turdus viscivorus)... Fieldfare (Turdus pilaris) Song Thrush (Turdus philomelos)... Redwing (Turdus musicus)... Ring Ouzel (Turdus torquatus) Blackbird (Turdus merula)... Wheatear (Oenanthe oenanthe) Whinchat (Saxicola rubetra)... Red-flanked Bluetail (Tarsiger cyanurus)... 9 Redstart (Phoenicurus phoenicurus) Thrush Nightingale (Luscinia luscinia) Bluethroat (Cyanosylvia svecica) Robin (Erithacus rubecula)... Grasshopper Warbler (Locustella naevia) Great Reed Warbler (Acrocephalus arundinaceus) Reed Warbler (Acrocephalus scirpaceus) Marsh Warbler (Acrocephalus palustris)... Blyth's Reed Warbler (Acrocephalus dumetorum) Sedge Warbler (Acrocephalus schoenobaenus) Icterine Warbler (Hippolais icterina) Blackcap (Sylvia atricapilla)... Barred Warbler (Sylvia nisoria) 8 Garden Warbler (Sylvia borin) Whitethroat (Sylvia communis) Lesser Whitethroat (Sylvia curruca) i Willow Warbler (Phylloscopus trochilus)... Greenish Warbler (Phylloscopus trochiloides) Chiffchaff (Phylloscopus collybita)... Wood Warbler (Phylloscopus sibilatrix)... Arctic Warbler (Phylloscopus borealis)... Goldcrest (Regulus regulus)... 5 Spotted Flycatcher (Muscicapa striata) Pied Flycatcher (Muscicapa hypoleuca) Red-breasted Flycatcher (Muscicapa parva) Dunnock (Prunella ^nodularis) Meadow Pipit (Anthus pratensis) 3 Tree Pipit (Anthus trivialis) Red-throated Pipit (Anthus cervinus) Rock Pipit (Anthus spinoletta) White Wagtail (Motacilla alba) 135,000 3,000 8,000 (+) 110, , , ,000 18,000 30, , ,000 1,400,000 21,000 33,000 6, , , , , , , , (*) 670, , ,000 So (+) 5-i ,000 10, , , ,000 5,700,000 1, ,000 36, , , ,000 8, ,000 1,650, (*) 500 (*) 430,000

6 VOL. LII] SPECIAL REVIEW: FINNISH BIRDS 27 Yellow Wagtail (Motacilla flava thunbergi) 400,000 Waxwing (Bomby cilia garrulus) 5,000 Great Grey Shrike (Lanius excubitor) 4,000 Red-backed Shrike (Lanius cristatus collurio). 9,000 Starling (Stmnus vulgaris) 170,000 Greenfinch (Chloris chloris)... 30,000 Goldfinch (Carduelis carduelis) 1,000 Siskin (Carduelis spinus) 410,000 Linnet (Carduelis cannabina) i,8oo (t +) Redpoll (Carduelis flammea) Arctic Redpoll (Carduelis hornemanni) 470,000 Bullfinch (Pyrrhula pyrrhula) Scarlet Grosbeak (Carpodacus erythrinus) 80,000 3,000 Pine Grosbeak (Pinicola enucleator) Crossbill (Loxia curvirostra) 17, ,000 Parrot Crossbill (Loxia pytyopsittacus) 30,000 (+ +) 2 Chaffinch (Fringilla coelebs). 5,300,000 7 Brambling (Fringilla montifringilla) 870,000 6 Yellowhammer (Emberiza citrinella) 970,000 Yellow-breasted Bunting (Emberiza aureola) Ortolan Bunting (Emberiza hortulana),000 Rustic Bunting (Emberiza rustica) Little Bunting (Emberiza pusilla) 380,000 2,500 Reed Bunting (Emberiza schoeniclus),000 Lapland Bunting (Calcarius lapponicus)... 14,000 Snow Bunting (Plectrophenax nivalis) 9,000 House Sparrow (Passer domesticus) 500,000 Tree Sparrow (Passer montanus) Total for Finland: ca. 32,160,000 (of which 31,620,000 are terrestrial) on 337,000 square kilometres or just over 73 million acres, averaging about 85 breeding adults per acres. This most interesting Table raises many questions regarding both the picture which it presents of the Finnish avifauna and the reliability and applicability of such estimates in general and of this one in particular. Taking the figures first of all at their face value, we learn that Finland's ten commonest breeding species are (in order) Willow Warbler and Chaffinch (at very similar levels of around 5J million), Tree Pipit, Willow Tit, Spotted Flycatcher, Yellowhammer, Brambling, Garden Warbler, Redstart and Crested Tit. On this information alone, no ornithologist would be surprised to learn that 65% of the area of Finland is under forest and only 8% is cultivated, or that it is a northern land in which summer residents form a large part of the breeding population. The most numerous bird appreciably over six inches long is the Song Thrush which comes eleventh (outnumbering the Blackbird by 80-1). Seven other forest species and the House Sparrow are clustered fairly near the half-million mark on the table. Besides the Blackbird, several other high-ranking British species come in at very low figures, such as Starling (170,000 - barely enough to populate one first-class roost), Rook (3,000), Blue Tit (18,000), Dunnock (8,000) and Wren (6,000) in striking

7 28 BRITISH BIRDS [VOL. LII contrast to the woodland Robin (410,000) and the gulls, none of which except the Black-headed exceeds 5,000 pairs. While divers and grebes reflect the extensive inland waters (covering 9% of Finland), ducks are not strikingly numerous, the Mallard alone reaching six figures, although the estimates for this group are inevitably only rough. Birds of prey, although varied, are in disappointingly small numbers, the Golden Eagle, Buzzard (?) and Peregrine being certainly even less numerous than in Britain. On the other hand, certain temperate species are surprisingly high such as Wryneck (perhaps a thousand times more numerous than with us), Golden Oriole, W r ood Warbler and Ortolan. Also, Finland is now at or near the western limit of the range of several species that are expanding from the east such as Terek Sandpiper and Blyth's Reed, Greenish and Arctic Warblers. Coming to Finland's special attractions, who can blame the tally-hunter for lingering over the pairs of Red-necked Grebe, 30 of White-tailed Eagle, 10 of Gyr Falcon, 8,500 of Crane, 1,500 or more of Turnstone, 50 of the declining Great Snipe, 11,000 of Broad-billed Sandpiper, 700 of Caspian Tern, 3,600 of Hawk Owl, of Pygmy Owl, 700 of Ural and 1,500 of Tengmalm's Owl, 23,000 of Three-toed Woodpecker, 10,000 of Shore Lark and many others including 500 of Redflanked Bluetail (an especially uncertain figure), of Yellowbreasted Bunting and 3,000 of Scarlet Grosbeak. Whatever else the list may achieve it certainly kindles the imagination. Coming down to earth, however, anyone who has both counted birds and seen Finland is bound to be faced with some scepticism as to the validity of such figures covering an area nearly half as large again as Great Britain and much more difficult to work. While the underlying data are candidly treated it is difficult to assess from them the adequacy of the sample on which this magnificent superstructure rests. Rather casual scrutiny indicates that each individual actually observed in the sampling is normally multiplied between 300 and times in framing the estimate. It is clear that great ingenuity and perseverance over many years have been devoted to securing a correct definition of habitats and a representative selection both of these and of zoological regions, but at the end of the day what does the margin of error amount to? Mr. J. G. Skellam, head of the Biometrics Unit of the Nature Conservancy, has kindly examined the basis of these estimates which is given in more detail in Dr. Merikallio's 1946 paper entitled "Uber regionale verbreitung und anzahl der Landvogel in Sud- und Mittelfinnland, besonders in deren Ostlichen Teilen, im Lichte von Quantitativen Untersuchungen" (Annates Zoologici Societatis, Tom. 12, nos. 1 and 2). Dr. Merikallio also courteously and informatively answered numerous questions on the subject. Although the material and knowledge available to us here is

8 VOL. LII] SPECIAL REVIEW: FINNISH BIRDS 29 evidently far more limited than that commanded by Dr. Merikallio and his colleagues, statistical examination confirms what ornithological experience would indicate, that such national bird population estimates based on samples of this type and scale are not at all to be relied upon. The margins of error are much too great, even those inherent in the sampling procedure itself being inacceptably large except for the very commonest species. What we have here, therefore, is not to be taken as a bird census of Finland or even as a serious approach to it. The study is rather an ambitious exercise in the application of painstaking but still limited and somewhat rough sampling methods in combination with a picture of national ecological and land-use patterns in a well-worked and relatively simple but rather large area. On these bases a gossamer network of arithmetic has been thrown boldly across Finland's immense forests and innumerable lakes to catch the whole bird population, but the real avifauna escapes the net and the forests keep their secrets. Must we then conclude that all this impressive industry has been wasted? Certainly not, provided that its limits and uncertainties are strictly understood. Being based as it is on regional samples which can be repeated periodically it will provide an excellent means of tracing future major changes in distribution of common species within Finland, possibly related, say, to climatic changes. For example, it has shown already that the decline during the 1930's and 1940's of Bramblings in middle Finland has lately been entirely reversed, so that the view put forward by O. Kalela (1952, Fennia, vol. 75, p. 48) of a climatically linked, clearly definable change in the mutual abundance relations of the "boreal" Brambling and the "southern" Chaffinch can no longer be sustained. Used in such ways Dr. Merikallio's figures afford measures of population density, differing perhaps for different species, but nevertheless reasonably consistent for comparative purposes in different habitats in different parts of the country. This is a very different matter from a national bird population census in which, as Dr. Merikallio himself points out, the sampling basis becomes completely unreliable for the scarcer or more patchily distributed species, including all those breeding in colonies or fluctuating markedly from season to season. Here Dr. Merikallio's valour has outrun his discretion. Nevertheless, even if such a Table as that given above must rank at this stage as largely a work of the imagination, it is for all that a real advance. It presents us with a model of the possible eventual results of a national bird census which enables us to see more clearly what the uses, limitations and problems of such a census would be, as well as the nature of the difficulties still to be overcome and the magnitude of the effort necesary to reduce margins of error to an acceptable level. Looked at in this way the task is

9 30 BRITISH BIRDS [VOL. LII certainly daunting, but modern ornithological history gives no ground for supposing that somewhere, sometime, it will not be successfully accomplished, perhaps sooner than we think. When that time comes Dr. Merikallio will deserve, and no doubt receive, the recognition due to a pioneer.