The avifauna of Białowieza· Forest: a window into the past Ludwik Tomiałojć and Tomasz Wesołowski

94. Pygmy Owls Glaucidium passerinum may number 30-50 pairs in the Polish part of Białowieza˙ Forest in a good year. Günter Bachmeier

ABSTRACT As a result of some 500 years of protection, parts of the Białowieza˙ Forest, in Poland, remain in a near-primeval condition. Studies of the breeding in the core part of the forest (Białowieza˙ National Park) over 29 years show that the community is species-rich but that densities of individual species are usually low, resulting in only moderate overall densities. In some species, low densities are a consequence of large territories and social exclusion, but more often they reflect the undersaturation of habitats by birds, despite superabundant food supply and nest-sites. Low productivity, resulting from high nest predation, may contribute to undersaturation. Species composition and numbers of birds fluctuate within relatively narrow limits, with the populations of closely related species fluctuating either independently of one another or in parallel; interspecific competition for resources plays a minor role. Some attributes of the Białowieza˙ ecosystems resemble conditions in undisturbed tropical forests but contrast sharply with those in fragmented, temperate secondary forests.The present Białowieza˙ avifauna provides a glimpse of that existing in central European forests before their historical transformation by humans. Its present exceptional character arises from

174 © British Birds 98 • April 2005 • 174-193 The avifauna of Białowie˙za Forest

preservation of most of its pristine features.The forest constitutes a critical reference point for studies of woodland ecology, and its preservation should be a high priority. Unfortunately, commercial logging continues, gradually changing the forest’s structure and affecting the birds, especially those dependent on dead wood and old-growth.The relatively small national park (47.5 km2) is increasingly becoming an ‘island’, in which the long-term preservation of primeval forest features will be impossible.

ur knowledge of the bird biology of so it is still possible to study birds living in near- pristine forest is full of gaps or misin- pristine conditions. Oterpretation, for the simple reason that The importance of studying European most temperate forests had been transformed woodland birds in pristine habitats became extensively by humans before modern research clear when one of us (LT) visited Britain in started. Consequently, any studies conducted in 1974 at the invitation of the BTO, and realised remnants of ancient temperate woodland are that the habits of birds in fragmented British important, providing crucial baseline data woods were strikingly different from those of against which to measure research from sec- birds occupying larger forests in central Europe. ondary or ‘man-made’ woodlands (Tomiałojć et These findings led to the launch (in 1975) of a al. 1984; Blondel 1995; Angelstam et al. 1997). comprehensive programme of ornithological In Europe, apart from some still extensive studies in the remaining tracts of primeval boreal (taiga) woodland, only two areas in the forest in BiałowieŻa National Park, which has transitional boreal-nemoral zone have retained developed into a long-term (almost 30 years) a substantial proportion of their near-primeval project. In this paper, we summarise the major mixed deciduous-coniferous forest. These are findings of this project, distilled from more the Berezinskiy Zapovednik, in northeast technical papers and reviews. Given that British Belarus (Byshnev 1991), and the BiałowieŻa forests and their birds may once have shared (pronounced ‘Byawovyezha’) Forest on the many of the characteristics of present-day Belarus/Polish border. For millennia, these BiałowieŻa (Tomiałojć 2000), this provides forests were probably quite ordinary parts of readers with an insight into the past, to see how the central European woodland; their present forests and their birds functioned without outstanding position stems from preservation serious human interference. We also hope that of their ancient features (Tomiałojć & this paper will encourage readers to visit Wesołowski 2004). BiałowieŻa owes its survival BiałowieŻa, and to support the struggle to pre- to around 500 years of consistent protection, serve the entire BiałowieŻa Forest for future initially as a prestigious hunting ground for generations. Polish kings and, later, Russian tsars. In the twentieth century, the care by rulers has been Study area and methods replaced by formal nature protection. A small Białowieza˙ Forest part of the forest, some 47.5 km2, has been Situated on the Poland/Belarus border, strictly protected as a nature reserve since 1921, BiałowieŻa Forest (BF), which occupies about and this core part of the forest is termed 1,500 km2 (fig. 1), lies at approximately the BiałowieŻa National Park. Apart from some same latitude as Birmingham (the co-ordinates limited intrusion by humans (a few small clear- of BiałowieŻa village are 52° 41’N 23° 52’E), cut or burnt patches), this area has remained within the transition zone between boreal and continuously under forest cover for approxi- nemoral forests, where Norway Spruce Picea mately seven millennia, so its forest ecosystems abies contributes to most types of local tree- have been shaped by natural ecological stands. The area is low (mostly 165-170 m processes without direct human intervention. above sea level) and flat, the climate subconti- Despite quite extensive, and worrying, recent nental, with warm summers and fairly cold changes in the neighbourhood, which we winters, sometimes quite severe (snow up to discuss below, these processes still operate there, 1 m deep, temperatures dropping to -25°C), Footnote: ‘nemoral’: the temperate broadleaf forest zone and with a growing season of c. 208 days. For

British Birds 98 • April 2005 • 174-193 175 The avifauna of Białowie˙za Forest © Fluke Art © Fluke Fig. 1. Map of the whole Białowieza˙ Forest and its surroundings, showing three zones of its protection and the contraction of the former high-forest area. BNP denotes the Polish Białowieza˙ National Park (composed of two protection zones). Key: 1 strictly protected parts of the neighbouring two national parks; 2 remaining parts of both national parks; 3 the Polish managed part shown jointly with its partly managed nature reserves; 4 main human settlements; 5 dam reservoir; 6 forest boundary in the seventeenth century; 7 present forest boundary; 8 state border.

details, see Faliński (1986, 2002), Tomiałojć & uprooted trees There is a great deal of dead Wesołowski (1990, 1994) and Jędrzejewska & wood – standing trees, stumps, freshly Jędrzejewski (1998). uprooted trees and old fallen logs – on The BF primeval stands are distinctive average 130 m3/ha in oak-lime-hornbeam among European temperate forests owing to stands (Bobiec 2002). There are many root- certain features which are characteristic of rich pads (discs of flat root-systems of uprooted pristine forests in various climatic zones. These trees), some rising vertically up to 7.5 m, are as follows: forming ‘walls’ up to 10-20 m long, and con- stituting a structure intermediate between • Multi-storey profile of stands In particular, the ground and the tree-layers (plate 95). those of the oak Quercus-lime Tilia-horn- • Impressive tree height The maximum height beam Carpinus type can be subdivided into for Norway Spruces in BF is 55-57 m, and 5-6 layers. Huge spruces, which rise 10-15 m for some deciduous tree species 42-45 m above the main canopy, are the equivalent of (Faliński 1968, 1986). the emergents of tropical forests. • Diverse tree community BF stands harbour • Large amounts of dead timber, with many 26 species of trees and 55 shrub species. The

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oak-lime-hornbeam stands alone may be dead wood and covering some 22% of BNP; composed of a dozen or so tree species. They and (iii) mixed coniferous forests (plate 98, are also strongly diversified according to the p 184), dominated by spruces and Scots Pine age (up to 400-500 years old) and size of the Pinus sylvestris (covering 28% of BNP). The trees. More details and photographs are remaining parts are composed of old meadows given in Tomiałojć et al. (1984), Faliński partially overgrown by secondary woodland. (1986), Tomiałojć & Wesołowski (1990, Beginning in the late nineteenth century, the 1994, 2004). hunting records of BF birds were collected with varying intensity in different periods. Those Long-term ornithological research phases of extensive, qualitative surveys are sum- Most of our detailed studies were carried out in marised in Borowski & Okołów (1988) and the strictly protected fragment of the Tomiałojć (1995, 2001). Our own intensive, BiałowieŻa National Park (BNP; fig. 1). quantitative studies began in 1975, focusing on Although the park was enlarged to 105 km2 in the ecology and behaviour of birds breeding in 1996, in this paper we define BNP as the strictly the primeval old-growth stands. We have exam- protected older part, comprising 47.5 km2, ined the structure and dynamics of whole which has remained free of human intervention breeding communities, as well as the long-term since 1921 and has at no time been affected by dynamics of individual species. We have also forest exploitation other than localised charcoal investigated how variation in environmental production or cattle grazing (Faliński 1968). conditions (e.g. weather, food, predators) influ- Most of the BNP area is covered by three types ences bird numbers. Long-term data on popula- of old-growth stands: (i) oak-lime-hornbeam tion sizes originate from territory-mapping on forest (plate 96, p 181), the richest in terms of seven permanent census plots, each 24-33 ha in tree species and structurally the most diverse, size (see Wesołowski et al. 2002 for a description and also the most extensive (covering some of methods). In addition, we have carried out 44% of the BNP area); (ii) swampy deciduous intensive population studies on the breeding forests (riverine stands and alder Alnus carrs, ecology and behaviour of 12 species. plate 97, p 183), with the greatest quantity of ć oj ł L.Tomia 95. One of the largest uprooted spruce Picea root-systems (‘rootpads’) in Białowieza˙ Forest, the breeding site of several bird species.

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Results: the breeding avifauna of high similarity of species composition in dif- primeval forest ferent forest types, we suggest that there is just a High species richness but moderate densities single old-growth breeding bird community in On average, about 35 (29-41) species bred in a BNP, with local variants (Tomiałojć et al. 1984; census plot of 24-25 ha in oak-lime-hornbeam Wesołowski et al. 2002b). forest in a single season. In a slightly larger (33 Extremely high species richness apparently ha) and more structurally diverse forest-edge stems to some extent from the geographical riparian patch, up to 52 species could breed in a position of BF (within the transition zone single year and 72 species bred at least once between western and eastern Europe, and during 25 years (Wesołowski et al. 2002b). The between predominantly coniferous and decid- latter figure may be compared with c. 75 forest uous forest; see Tomiałojć 2000) and from the and forest-edge species breeding in the whole of retention of most of its avifauna (i.e. with few Britain (Simms 1971). Pooling data from the extinctions; see below). More importantly, it three types of old-growth forest stands studied seems to reflect the fine-scale diversity within at BNP (all census plots, 187.5 ha in total) pristine forest stands, which offers various increases the number of breeding species only microhabitats (e. g. snags, holes, rootpads, tiny to 80 (Tomiałojć & Wesołowski 2004). This water pools) to satisfy the requirements of indicates that in BNP many species breed many species. Our data show that, in deciding alongside one another in the same spot and that where to settle, birds are more influenced by the the majority are able to breed across all/most structural properties of a patch of woodland types of the old-growth forest. Even gaps in the than by the general type of habitat (Wesołowski old-growth stands created by windthrow (the et al. 2002b; Tomiałojć & Wesołowski 2004). uprooting and felling of trees by strong winds), Only a minority of species in BNP show clear though different structurally, do not usually habitat specialisation, and these birds are attract new species (Fuller 2000). Owing to the mostly restricted to riverine stands (e.g. Lesser

Box 1. The avifauna of Białowieza˙ Forest. This gives a summary of the main bird groupings which occur in the forest. Full documentation is available in Borowski & Okołów (1988),Tomiałojć (1995, 2001),Tomiałojć & Stawarczyk (2003) and Wesołowski et al. (2003).

Waterfowl In pristine BiałowieŻa Forest (BF), this group was poorly represented. Judging from present-day habitat requirements and historical data, the native species were those which favour marshland, for example the common dabbling ducks (Mallard Anas platyrhynchos, Eurasian Teal A. crecca, Garganey A. querquedula, Shoveler A. clypeata), Little Grebe Tachybaptus ruficollis,Grey Heron Ardea cinerea. During the last 40 years, this group has been enriched by construction of artificial lakes within the forest in the Belarussian part, which have attracted further breeding species (including Mute Swan Cygnus olor, Greylag Goose Anser anser, Gadwall Anas strepera, Common Pochard Aythya ferina, Tufted Duck A. fuligula, Ferruginous Duck A. nyroca and Common Goldeneye Bucephala clangula). Gamebirds Two formerly common forest grouse, Capercaillie Tetrao urogallus and Black Grouse T. tetrix,are on the verge of local extirpation, though some hundreds were reported as recently as the 1920s. There is no evidence that they breed currently in BNP; only a few still survive in the Belarussian part of the forest. Hazel Grouse Bonasa bonasia is still widespread, while Grey Partridge Perdix perdix and Common Quail Coturnix coturnix are scarce breeding species among larger glades. Storks Both species breed in good numbers. Black Stork Ciconia nigra is native to the area, while only speculative argument can be offered for the provenance of White Stork C. ciconia. Diurnal raptors The most numerous breeding species are Common Buzzard Buteo buteo and Honey-buzzard Pernis apivorus, followed by Lesser Spotted Eagle Aquila pomarina (c. 60 pairs in the Polish part of the forest), while Northern Goshawk Accipiter gentilis and Eurasian Sparrowhawk A. nisus are less numerous. Other species, such as Booted Hieraaetus pennatus and Short-toed Eagles Circaetus gallicus, Montagu’s Circus pygargus and Marsh Harriers C. aeruginosus and Hobby Falco subbuteo, occur on both sides of the state border, with just a few pairs in each part. Single pairs of Black Milvus migrans and Red Kites M. milvus have bred only sporadically, while a pair of Golden Eagles Aquila chrysaetos recently resettled in the Belarussian part of the forest. Breeding by Hen Harrier C. cyaneus and Peregrine Falcon F. peregrinus was documented only for the period prior to the 1960s; a few pairs of Spotted Eagles A. clanga have recently been rediscovered in the eastern part, and during the 1990s a pair of White-tailed Eagles Haliaeetus albicilla settled to breed in the Belarussian part of the forest. Common

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Spotted Eagle Aquila pomarina, Common cases) is the most numerous species, while Crane Grus grus, Green Sandpiper Tringa locally, and in some years, Collared Flycatchers ochropus) or coniferous forest (e.g. Pygmy Ficedula albicollis outnumber them in the oak- Glaucidium passerinum and Tengmalm’s Owls hornbeam stands (Walankiewicz et al. 1997). Aegolius funereus, Nutcracker Nucifraga cary- The group of relatively abundant species also ocatactes). contains Robin Erithacus rubecula and Song The occurrence of many breeding species in Thrush Turdus philomelos (all habitat types), one area might lead to a high overall bird sometimes Wood Warbler Phylloscopus sibila- density, but this is not the case in BNP. Overall trix (mostly dry stands), Blackcap Sylvia atri- densities range from about 40 pairs/10 ha in capilla (mostly swampy forest), Hawfinch coniferous forest to almost 120 pairs/10 ha in Coccothraustes coccothraustes (oak-hornbeam the riverine plot at the forest edge (fig. 2). habitat), Goldcrest Regulus regulus and Coal These levels are no higher than in managed Tit Parus ater (coniferous forest), and woodlands of Germany or England (Flade Common Starling Sturnus vulgaris (forest 1994; Fuller 1995), but several times lower edge). The densities of most other species than those found in fragmented English woods remain below 3 pairs/10 ha; these constitute, (e.g. 400 pairs/10 ha in Somerset or up to 252 on average, 58% of the breeding-bird list in pairs/10 ha in Wytham Woods, Oxfordshire; riverine forest and up to 71% in the coniferous Parsons 1976, BTO data). Moderate overall forest (Tomiałojć & Wesołowski 2004). Many of densities in BNP result from low densities of the low-density species breed in much higher most constituent species; only a few species densities elsewhere in Europe, in woodland breed regularly at densities of more than 5 transformed by human activity, e.g. Wood pairs/10 ha (Tomiałojć et al. 1984; Wesołowski Pigeon Columba palumbus – up to 240 times et al. 2002b). As a rule, Common Chaffinch higher; Blackbird T. merula – 40 times; Great Fringilla coelebs (>20 pairs/10 ha in some Tit P. major – 10 times; and Wren Troglodytes

Box 1. The avifauna of Białowieza˙ Forest. continued Kestrel F. tinnunculus no longer breeds in BF. Gruiformes All species, with the possible exception of Common Coot Fulica atra, are native. Most are still wide- spread (including Corn Crake Crex crex and Common Crane Grus grus), while some (e.g. Spotted Porzana porzana and Little Crakes P. par va) must have declined after the drainage of wetlands. Charadriiformes As a group of native BF birds, the waders suffered marked reduction in abundance and species richness after wetland reclamation. Only the ‘forest’ species, including Woodcock Scolopax rusticola, Common Snipe Gallinago gallinago and Green Sandpiper Tringa ochropus, have remained fairly common, though probably all have declined during the recent dry years. Other species have disappeared or been reduced to irregular breeding pairs, restricted to remaining marshes of the eastern part: Great Snipe Gallinago media, Black-tailed Godwit Limosa limosa, Eurasian Curlew Numenius arquata and Tringa totanus. Ruffs Philo- machus pugnax no longer breed in BF, while Marsh Sandpipers Tringa stagnatilis occasionally breed in the neigh- bouring Siemanówka dam lake. Artificial lakes have attracted breeding Black-headed Gulls Larus ridibundus plus Common Sterna hirundo,Black Chlidonias niger and White-winged Black Terns C. leucopterus. Little Gull L. minutus breeds sporadically in the neighbourhood, at Siemanówka. Pigeons Of three native species, Wood Pigeon Columba palumbus is widespread though remarkably scarce and secretive, Stock Dove C. oenas is not uncommon, while the declining Turtle Dove Streptopelia turtur is a scarce breeder along the forest edges. Since the late 1950s, Collared Doves S. decaocto have bred in villages. Owls Of the nine species recorded as breeding in BF, all are native with the exception of Barn Owl Tyto alba and Little Owl Athene noctua, which are thought to have colonised during the 18th-19th centuries. Tawny Owl Strix aluco is the most numerous species, while Long-eared Asio otus,Pygmy Glaucidium passerinum and Tengmalm’s Owls Aegolius funereus occur patchily, also in BNP. During good years, in the Polish part of the forest, there may be 30-50 pairs of each of them. Between one and several pairs of Eagle Owl Bubo bubo, Little Owl and Barn Owl are still known. Great Grey Owl S. nebulosa, a real rarity, has recently been rediscovered in the Belarussian part, where there are a few pairs, while in the Polish part it is represented by only sporadic visitors. Short-eared Owls Asio flammeus bred irregularly in marshes during the 1940s. Coraciiformes and allies European Roller Coracias garrulus and Hoopoe Upupa epops are both declining. The

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120 research. Theoretically, two mechanisms could be involved. 100 Perhaps low density is a result of undersaturation – i.e. breeding 80 habitats are not fully utilised, and bird density is determined by the numbers surviving until (or 60 arriving in) the spring. In this

Pairs/10 ha case, all the birds present can 40 settle and breed, while social intolerance plays no role as a 20 limiting factor. Alternatively, the habitats could be saturated with 0 Riverine Oak-hornbeam Coniferous birds, and low densities arise from social intolerance; in other Fig. 2. Overall densities of the bird community in the Białowieza˙ National Park were consistently higher during the 1990s (black) than words, there are more would-be during the 1970s (grey); derived from Tomiałojć et al. (1984) and settlers than places to breed, and Wesołowski et al. (2002). some birds are excluded from breeding by social interactions. troglodytes – 8 times (Tomiałojć 1980, 1993; In this case, territorial behaviour and other Wesołowski 1983; Wesołowski et al. 1987). forms of social intolerance act as an important Given these statistics, the question of why limiting factor. the density of birds is so low in BiałowieŻa We found evidence for the operation of Forest compared with secondary woodland both mechanisms. The repopulation of experi- elsewhere in Europe became a focus for our mental areas by Wrens, Wood Warblers and

Box 1. The avifauna of Białowieza˙ Forest. continued former was once not uncommon in BiałowieŻa Glade (the oldest deforested glade in BF, some 13 km2 and dating back to the sixteenth century, and the setting for BiałowieŻa village – see fig. 1) and along BNP edges, but is now a rare visitor from its last remaining breeding sites north of BF. Hoopoe, formerly a common species, no longer breeds in the BiałowieŻa Glade, although it occurs along the edges of BF in small numbers. European Nightjar Caprimulgus europaeus is a regular breeder in the managed conifer-dominated plantations with clearings, while several dozen pairs of Common Swift Apus apus breed in high trees. BF is famous for its woodpeckers – nine breeding species, all native. Besides three common Den- drocopos species (Great Spotted D. major, Middle Spotted D. medius and Lesser Spotted D. minor), Black Dry- ocopus martius, White-backed leucotos and Three-toed Woodpeckers Picoides tridactylus occur regularly. Grey-headed Picus canus, the much scarcer Green Woodpecker Picus viridis and Wryneck Jynx torquilla settle mostly along the forest edges. Expanding its range from the south, the Syrian Woodpecker D. syriacus has been seen twice near BiałowieŻa. Larks and motacillids Of three breeding larks, two wagtails and three pipits, most are native species, but the Crested Lark Galerida cristata probably arrived in the late eighteenth century, when permanent forest-villages were established. Wood Lark Lullula arborea, which initially bred in burned areas and along forest edges, is fairly widespread in the drier clear-cut areas of the managed part. In addition, Citrine Wagtail Motacilla citreola has started to breed near the Siemianówka dam lake in recent years. Turdids Of 13 species of breeding Turdidae, there are three native thrushes plus Redwing Turdus iliacus; the last species has colonised BF edges and village parks since the 1950s. Fieldfare T. pilaris is remarkably scarce. Among the chats, Thrush Nightingale Luscinia luscinia is a widespread breeder, though recently declining; Common Red- start Phoenicurus phoenicurus is rather scarce; while Bluethroat L. svecica is on the verge of disappearing as a breeding bird. Black Redstart P. ochruros is a twentieth-century coloniser of villages in the forest, while Common Stonechat Saxicola torquatus is the newest coloniser, breeding since 1993. Warblers and kinglets No fewer than 18 warbler species breed. The only newcomer among them seems to be Greenish Warbler Phylloscopus trochiloides (usually only unmated males, although proved breeding has occurred on three occasions; Tomiałojć 1995 and unpubl.). Among the remaining species, there are three Locustella war- blers (including River Warbler L. fluviatilis, a common breeder, and Savi’s Warbler L. luscinioides, which is more

180 British Birds 98 • April 2005 • 174-193 The avifauna of Białowie˙za Forest ć oj ł L.Tomia 96. A fragment of the oak Quercus-hornbeam Carpinus forest in the Białowieza˙ National Park, the habitat with densest populations of Collared Flycatcher Ficedula albicollis and Hawfinch Coccothraustes coccothraustes.

Box 1. The avifauna of Białowieza˙ Forest. continued locally distributed), four common Acrocephalus warblers (including Marsh A. palustris and Great Reed Warblers A. arundinaceus), plus – once breeding in BF marshland, and maybe still – Aquatic Warbler A. paludicola.Among the other warblers are five Sylvia representatives (including Barred Warbler S. nisoria, which is fairly common among clearings and young forest plantations), three common Phylloscopus species and Icterine Warbler Hippo- lais icterina. Both European kinglets occur, of which Firecrest Regulus ignicapilla is a scarce breeder (the first nest was found in BNP in 1975). Flycatchers All four breeding species, including Red-breasted Flycatcher Ficedula parva, are fairly common, while Collared Flycatcher F. albicollis is, in some years, the most numerous breeding species in oak-hornbeam stands in BNP. Tits and allies All six breeding Parus tits, Eurasian Nuthatch Sitta europaea and Eurasian Treecreeper Certhia familiaris are common and native. In old-growth stands of BNP, only Willow Tit P. montanus is scarce, though it is common in young willow-birch thickets and pine plantations. Short-toed Treecreeper C. brachydactyla does not breed in the area. Shrikes Red-backed Shrike Lanius collurio remains common among young managed stands and clearings, Great Grey Shrike L. excubitor is a scarce but regular breeder, while Lesser Grey Shrike L. minor was reported to breed not uncommonly during the 1940s, and scarcely until 1981. The few remaining pairs of this species in Poland breed in the agricultural areas north of BF. Corvids BF harbours three native corvids (Eurasian Jay Garrulus glandarius, Nutcracker Nucifraga caryocatactes and Common Raven Corvus corax). Two others, very scarce until recently, Magpie Pica pica and Hooded Crow C. cornix, may have bred in larger river valleys in pristine times. Two further species arrived later: Western Jackdaw C. monedula breeds sporadically in human settlements among larger glades, while Rook C. frugilegus breeds only in Hajnówka town. Other passerines Apart from granivorous passerines common in central Europe, Siskins Carduelis spinus and Common Crossbills Loxia curvirostra breed in highly variable numbers. All but House Sparrow Passer domesticus, Serin Serinus serinus and Common Rosefinch Carpodacus erythrinus are native to the area. The last species has bred in BF since the 1950s, and is now widespread. Among the four breeding buntings, Ortolan Emberiza hortu- lana and Corn Buntings E. calandra are most probably the newcomers, the latter rare until now.

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Great Tits after the removal of territory owners shown no consistent change during the 25 shows that some males of these species may be years of our research, but mean overall densi- prevented from establishing territories at den- ties, in all plots, were 50% higher in the late sities as low as 1.5-2 territories/10 ha 1990s than during the late 1970s (Wesołowski (Wesołowski 1981; Wesołowski et al. 1987; et al. 2002b). This reflects the increasing popu- Wesołowski & Tomiałojć 1995). Nonetheless, lations of several species, notably Blackbird, spatial undersaturation is also a common phe- Collared Flycatcher, Marsh Tit Parus palustris nomenon. For example, an area which con- and Chaffinch. The fact that the increasing tained 21 Wood Warbler territories in one species differed so much in their food require- season remained empty in another, without any ments, nest-sites and migratory patterns sug- noticeable change in forest structure or food gests that a number of causal factors were resources (Tomiałojć et al. 1984; Wesołowski & responsible. Neither severity of winter weather Tomiałojć 1995). Furthermore, Eurasian nor variation in seed crops, rodent numbers or Nuthatch Sitta europaea territories did not caterpillar abundance (see below) showed com- occupy all the available space, even in years of parative long-term trends in the forest which relatively high numbers, and undersaturation could account for the observed increases probably occurred most of the time in this (Wesołowski & Tomiałojć 1997; Wesołowski et species (Wesołowski & Stawarczyk 1991), al. 2002b; Wesołowski 2003). Nonetheless, in while, in poor years at least, Great Tits were spite of the trend of increasing numbers, the probably not sufficiently numerous to fill the narrow limits within which populations varied available space (Wesołowski et al. 1987). are remarkable when compared with the mag- Some characteristics of the BNP breeding nitude of changes recorded in other habitats avifauna (high species richness, few dominants, over the same period, such as the upheaval in prevalence of rare species) are similar to those farmland bird communities in western Europe recorded in tropical rainforests. This suggests (e.g. Donald et al. 2001, Schifferli 2001). Of that natural differences in species richness and course, the variation in bird numbers in BNP is breeding bird community structure between trivial when compared with that of rodent temperate and tropical forests may have been numbers in the same area (over 40-fold), the less pronounced in the past, and that contem- hornbeam seed crop (over 900-fold) or the porary differences owe much to man-made numbers of defoliating caterpillars (up to transformation of most temperate forests. 2,000-fold) (Wesołowski & Tomiałojć 1997; unpubl. data). Long-term stability in a variable world Changes in numbers of birds, even closely Species composition and species richness have related species, were mostly independent of one another, or positively correlated 240 (Wesołowski & Tomiałojć 1997; T. merula Wesołowski 2003; fig. 3). Such T. philomelos a pattern of changes does not 200 support the idea of tightly organ- ised, saturated, resource-tracking, competitively interacting bird 160 communities (MacArthur 1972). Rather, the BNP breeding bird community is a loose assemblage 120 of species, living together yet largely independent of one

Population index (% of 1977 value) Population another. Frequent undersatura- 80 tion and lack of close coupling 1975 1980 1985 1990 1995 2000 between resources and changes in bird numbers (see below) Fig. 3. Several congeneric species pairs, such as Blackbird Turdus merula indicate that interspecific and Song Thrush T. philomelos shown here, exhibit non-compensatory competition has apparently been changes in their abundance (i.e. their populations are largely independent of one another) in Białowieza˙ National Park; from Wesołowski & relatively unimportant Tomiałojć (1997) and Wesołowski et al. (2002). (Wesołowski 2003).

182 British Birds 98 • April 2005 • 174-193 The avifauna of Białowie˙za Forest

Pristine features in habitat utilisation interspecific competition for them (reviewed in The interior of BNP is more than 10 km from Newton 1998). Yet holes are superabundant in extensive farmland, and 3 km from small fields BNP (Wesołowski 1989, 1996, 2002; in forest clearings. Despite this, it is inhabited Walankiewicz 1991, 2002; Wesołowski & by Honey-buzzards Pernis apivorus, Common Rowiński 2004) and interspecific conflicts over Buzzards Buteo buteo, Stock Doves Columba this resource hardly occur. Tree holes and cavi- oenas, Wood Pigeons, Common Swifts Apus ties are so abundant that even Wrens, Dunnocks apus and Blackbirds. When breeding deep in the Prunella modularis, Robins and Blackbirds nest forest, these birds do not fly to distant fields but in them frequently. In the case of Blackbird, forage locally, in the forest (Tomiałojć et al. c. 49% of nests may be in holes or cavities with 1984; Tomiałojć & Wesołowski 1994; Jędrze- large entrances (Tomiałojć 1993). This demon- jewski et al. 1994a; van Manen 2003). This strates that population limitation of hole- implies that, originally, these were interior- nesting species by shortage of nest-sites and forest species and that they developed a ten- strong interspecific competition for them could dency to exploit open-land food resources as be new for this group of birds, something they European woodland was fragmented. Con- have experienced rarely in their evolutionary versely, two species which breed commonly in past, for example in (formerly rare) extensive fragmented woods elsewhere in Europe retain a young forest patches. markedly restricted distribution in BF: in most years Starlings breed exclusively along the forest Severe winters are not normally detrimental edges, while Tree Sparrows Passer montanus do Bird populations in the temperate zone are not breed in the forest at all, being found only often limited by food resources during the non- where there are human settlements (Tomiałojć breeding season and by harsh winter weather. et al. 1984; Wesołowski et al. 2003). As the winters of eastern Poland are harsher than those of western Europe (with snow cover Hole-nesting birds are not limited by a lasting up to three months and temperatures shortage of holes dropping below -20°C), one would expect birds Hole-nesters serve as a textbook example of in BiałowieŻa to be strongly affected by severe species limited by a shortage of nest-sites and weather, but this is only partially true. Many ć oj ł L.Tomia 97. The riverine ash Fraxinus-alder Alnus stand in Białowieza˙ Forest, characterised by the richest ground- and bush-layers.

British Birds 98 • April 2005 • 174-193 183 The avifauna of Białowie˙za Forest

conditions to influence the numbers of Nuthatches, Great Spotted Woodpeckers, tits and Siskins Carduelis spinus in spring (Wesołowski 1994). These species regularly forage on tree seeds in the non- breeding period, as well as in early spring. The numbers of BiałowieŻa residents, however, were dependent neither on deciduous tree seeds nor on those of spruce (Wesołowski 1994; Wesołowski & Tomiałojć 1997). This was a completely unexpected finding, as the seed supply has a dramatic effect on local mammals, with rodent outbreaks in mast years (Pucek et al. 1993). Although they utilise tree seeds, the birds in BNP appear to be less depen- dent on particular types of seeds than elsewhere. This may be because of the higher local diversity of alternative food, as the BNP deciduous stands are composed of 10-12 tree species. In such multi-species and multi-aged stands, the birds can ć oj

ł switch to alternatives when one particular food source fails,

L.Tomia without any appreciable effect 98. A gap in the mixed coniferous (spruce Picea-pine Pinus) stand (Wesołowski 1994; Wesołowski in Białowieza˙ Forest, with some deciduous tree species. & Tomiałojć 1997). Observa- species, including Wren, Robin, Starling and tions showing that birds in these primeval con- Chaffinch, migrate to areas with a milder ditions hardly ever use bird feeders climate (primarily to southwest or west-central (Wesołowski 1995) support this explanation; Europe). The local residents, as a group, are even in winter there is adequate food supply for affected by winter severity, and we found that both insectivores and seed-eaters. Deep snow overall numbers were positively correlated with cover can spell trouble for rodent eaters, temperatures in the preceding winter (mean however, as shown by a marked decline in temperature in December-March; Wesołowski Tawny Owls Strix aluco after the unusually 1994; Wesołowski & Tomiałojć 1997). Nonethe- snowy winter of 1995/96 (Jędrzejewska & less, at the species level, only Middle Spotted Jędrzejewski 1998). Woodpecker Dendrocopos medius and Goldcrest were strongly affected by harsh winters, while Spring food resources are usually abundant others showed either no correlation (e.g. Great Invertebrate specialists comprise c. 85% of the Spotted Woodpecker, Nuthatch, Eurasian local breeding-bird assemblage and approxi- Treecreeper Certhia familiaris) or weak correla- mately half of these collect food in the tree tion (e.g. Marsh, Blue Parus caeruleus and Great canopy. Leaf-eating caterpillars constitute a Tits) with winter temperatures. substantial part of nestling diet, in some species In other forests and regions, the autumn 70-80% (e.g. Middle Spotted Woodpecker and seed supply often interacts with winter weather Marsh Tit; Wesołowski 2003). It might be

184 British Birds 98 • April 2005 • 174-193 The avifauna of Białowie˙za Forest Ray Tipper 99. Song Thrush Turdus philomelos is a common breeding species in all habitat types in Białowieza˙ Forest. Typically a highly secretive bird, it has only recently become more approachable along tourist trails through the forest. expected that numbers of insectivorous birds western Europe and North America, where would be strongly affected, either directly or caterpillar resources are often consistently low indirectly (via production of young), by the and signs of breeding-season food limitation enormous (up to 2,000-fold) variation in the have been observed (Holmes et al. 1986; geometrid caterpillar supply (Wesołowski & Newton 1998). Tomiałojć 1997; Wesołowski et al. 2002b). For While insectivores could apparently com- example, the defoliating Winter Operoph- pensate for missing geometrid caterpillars by tera brumata caterpillars usually occur in low switching to alternative food sources, this was numbers, with their outbreaks (which lead to not so with rodent specialists. Although partial or total defoliation of deciduous trees) Common Buzzards and Tawny Owls hunted usually 8-11 years apart (Wesołowski & mostly birds when rodents were unavailable, Tomiałojć 1997). Nonetheless, bird numbers these two species could not fully compensate were found to be largely independent of varia- for lack of their main prey, and laid smaller tion in caterpillar abundance, and numbers of clutches or postponed breeding during rodent only three of 13 crown insectivores were posi- crashes (Jędrzejewski et al. 1994a,b; van Manen tively correlated with this food source. Further- 2003). more, in all species studied so far, starvation and brood reduction were found to be unim- Predation strongly reduces bird productivity portant, even during the low caterpillar years In BF, birds face a diverse assemblage of preda- (Wesołowski 2003). Birds in BiałowieŻa laid tors, with over 30 species using various tech- clutches as large as or larger than the highest niques of prey detection and attack; compared values recorded elsewhere and polygyny with most European forests, predator diversity occurred frequently (Wesołowski 1987), neither here is two or three times higher (Tomiałojć et of which would be expected if food was in short al. 1984). As well as raptors, owls and corvids supply. This suggests that food resources for (see below), there are 11 carnivorous mammals. insectivores are usually superabundant during In descending order of abundance, these are the breeding season, and that the effects of food Weasel Mustela nivalis, Pine Marten Martes shortage or competition for food cannot martes, non-native Raccoon Dog Nyctereutes account for variation in bird numbers procyonoides, Polecat Mustela putorius,Red Fox (Wesołowski 2003). This contrasts markedly Vulpes vulpes, Stoat Mustela erminea, Wolf Canis with the situation in deciduous forests in lupus, Lynx Felis lynx,Badger Meles meles,Otter

British Birds 98 • April 2005 • 174-193 185 The avifauna of Białowie˙za Forest Paul DohertyPaul 100. The Honey-buzzard Pernis apivorus is one of the most numerous diurnal raptors in Białowieza˙ Forest, along with Common Buzzard Buteo buteo. Lutra lutra and American Mink Mustela vison Europe, nests were robbed mostly during the (replacing the now-extinct European species; nestling stage. This makes the losses especially Jędrzejewska & Jędrzejewski 1998). In addition, costly, since the majority of energy investment there are non-specialised species, such as Wild necessary for rearing a brood has already been Boar Sus scrofa, Red Squirrel Sciurus vulgaris, made and effort which could otherwise have Yellow-necked Mouse Apodemus flavicollis, been devoted to another nesting attempt has Forest Dormouse Dryomys nitedula and Great been wasted. Heavy predation continues after Spotted Woodpecker, which appear to be the chicks have fledged, when species such as important nest predators in BNP (Wesołowski Common Buzzard, Pygmy and Tawny Owls and 1985, 2002; Walankiewicz 2002). Pine Marten exploit this easy prey source Our research showed that nest losses in BNP (Jędrzejewski et al. 1994a,b; Zalewski et al. 1995; are much higher than in secondary woodland van Manen 2003). As a result of heavy preda- (Tomiałojć et al. 1977, 1984; Tomiałojć 1980; tion, the production of young per breeding pair, Wesołowski 1983). Breeding loss rates and especially the production of young per unit amounted to 60-70% in the majority of species, area, is generally low in BNP, sometimes an but some were even higher, up to 76% for order of magnitude lower than recorded in Wood Warbler (Wesołowski 1985), 84% for other woodlands (Wesołowski 1983; Hawfinch and 97% for Wood Pigeon Wesołowski et al. 1987; Tomiałojć 1994). Such (Tomiałojć 1997, 1999). Hole-nesters were gen- low productivity, even without heavy mortality erally more successful but, even in this group, in the intervening non-breeding season, leads to up to 70% of Collared Flycatcher broods were fewer would-be recruits the following spring, lost in some seasons (Walankiewicz 2002a). which in turn result in low breeding numbers. These figures exceeded or were equal to the Our data show that high predator pressure and highest losses recorded for the same species in low productivity are essential features of the human-transformed woodland (Tomiałojć birdlife in rich primeval forests, including tem- 1995). For all species studied, predation was perate ones. responsible for the majority (64-91%) of total nest loss, and year to year variation in nesting Nest-sites in primeval forest – looking for success was due mostly to varying predation safety rates, even in low caterpillar years (Wesołowski The diversified structure of primeval tree- 1983, 1985; Piotrowska & Wesołowski 1989; stands, incorporating heterogeneity within the Tomiałojć 1994). In contrast to other parts of ground layer (e.g. uprooted trees and decaying

186 British Birds 98 • April 2005 • 174-193 The avifauna of Białowie˙za Forest logs) and several canopy layers, provides a wide 2004). Using holes in living trees has some variety of microhabitats, some completely drawbacks, however, as the nest contents have missing in secondary woods, in which to to be prevented from getting wet. This seems to conceal nests. The superabundance of natural be the reason why secondary hole-nesters such holes in old-growth stands enables secondary as tits, flycatchers and Nuthatches pile their hole-nesters to choose their preferred hole holes with moss, leaves and bark flakes respec- types. Consequently, BNP provides an opportu- tively (Wesołowski 2002; Wesołowski et al. nity to investigate the role of ancient structures, 2002a; Wesołowski & Rowiński 2004). almost absent in managed stands, as nesting One general characteristic of the birds in substrate for birds, and also the role of nest BNP is the large variation in nest-site place- location in predator avoidance. In such areas of ment, according to availability and suitability of high predation pressure, inaccessible and/or particular substrates. For example, tree species well-hidden nest-sites have a high adaptive used by hole-nesters differed across habitat value. types (Wesołowski 1989, 1996; Wesołowski & So far, the nest-sites of over 20 species have Rowiński 2004). Seven main types of nest-site been studied, including representatives of all the were recognised in Blackbirds; in oak-horn- major nesting groups (ground-, crown- and beam stands, this species used mostly large cavi- hole-nesters; see Wesołowski & Tomiałojć 1995, ties and holes, limb bifurcations and offshoots Wesołowski 1996, 2002, Tomiałojć 1997, van on trunks of living trees, while in riverine Manen 2003, Wesołowski & Rowiński 2004, and stands it bred in snags and rootpads to a much Czeszczewik in prep.). The results confirm the greater extent (Tomiałojć 1993). Similar varia- importance of structures characteristic of tion was found in Chiffchaffs Phylloscopus colly- primeval forest. Rootpads are regularly used as bita: in dry habitats, the majority of nests were nest-sites by Wrens, Dunnocks, Robins, Spotted situated on the ground, among fallen branches, Flycatchers Muscicapa striata and three species while in riverine stands they were often built at of thrushes. In riverine stands, Blackbirds locate the base of fern and sedge tussocks and among over 30% and Wrens almost 80% of their nests fresh vegetation. In the latter habitat, the nests in them (Wesołowski 1983; Tomiałojć 1993). If other features missing from managed woods (e.g. snags, fallen logs) are added, it appears that 62-70% of Blackbird nests and up to 90% of Wren nests are found in structures usually non- existent in secondary woods. Reflecting the nature of the trees in BiałowieŻa, birds locate their nests much higher above the ground, and often in much larger trees, than in other parts of Europe. For example, Blackbirds breed up to 24 m above ground and woodpeckers up to 35 m above ground (Wesołowski & Tomiałojć 1986; Wesołowski 1989; Tomiałojć 1993; unpubl. data). All primary hole-nesters, with the exception of Great Spotted Woodpeckers, excavate holes in dead and decaying wood, either in snags or in dead fragments of living trees. Conversely, secondary hole-nesters tend to avoid such holes, and breed mostly in non-woodpecker holes in living trees, which gives some protection from Arnoud B. van den Berg predation by Great Spotted Woodpeckers 101. White-backed Woodpecker Dendrocopos (Walankiewicz 2002b; Wesołowski 2002). In the leucotos is one of nine native breeding woodpeckers case of Ficedula flycatchers, however, holes in in Białowieza˙ Forest.This old-growth forest specialist is currently in decline, and will undoubtedly continue dead-tree fragments constitute almost half of to suffer if forestry operations continue in those those used (Wesołowski & Tomiałojć 1995; parts of Białowieza˙ Forest which are not strictly Wesołowski 1996; Wesołowski & Rowiński protected.

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1991), but not by Blackbird, for which losses in riverine and oak-hornbeam habitats did not differ (Tomiałojć 1993). Whereas Chiffchaffs bred at the highest densities in ‘safe’ habitat, Wood Warblers clearly avoided it, breeding in low and highly unstable numbers (Wesołowski 1985; Tomiałojć & Wesołowski 1990; Wesołowski et al. 2002b). This apparently puzzling result can be explained by the fact that Wood Warblers invariably build their nests on the ground, often digging small pits, and so, in wet places, their nests are not protected against soaking and/or inundation (Wesołowski 1985; Piotrowska & Wesołowski 1989). In contrast, Chiffchaff nests in riverine forests were significantly more successful when the nests were sur- rounded by water, whereas nest losses increased sharply in drought years (Piotrowska & Wesołowski 1989). Generally, our results so far demonstrate that, of the two means of avoiding nest preda- Gordon LangsburyGordon tion – camouflage and inacces- 102. Tawny Owls Strix aluco are the most abundant of nine owl species to sibility – the latter was more have been recorded breeding in Białowieza˙ Forest.Although, like Pygmy Glaucidium passerinum and Tengmalm’s Owls Aegolius funereus, this species effective in BNP. Most open- will exploit the easy pickings of recently fledged chicks,Tawny Owls are nesting species attempted to essentially rodent specialists, and the species is prone to suffer during hide their nests (often they hard winters with heavy snowfall. were extremely well camou- were typically situated 5-20 cm above the flaged) as well as making them as inaccessible as ground, to prevent flooding (Piotrowska & possible. Owing to the high diversity of preda- Wesołowski 1989). Nests in wet riverine forests tors, with varied techniques of prey detection seem to be least accessible to ground-dwelling and attack, these precautions work only to a predators. Here, visibility is limited by luxuriant limited degree, and it seems that there is no ground vegetation, and ‘islands’ of vegetation such thing as a truly predator-proof nest loca- are surrounded by mud or water, while move- tion. ments of predators through the canopy are hin- dered by relatively large gaps among Discussion and future prospects small-crown trees. Consequently, such wood- From primeval to secondary forests land should be the safest habitat for breeding The characteristics of bird communities in birds. This was supported by studies of Wood primeval BNP stands differ markedly from Warbler, Chiffchaff and Nuthatch, for which those in man-made forests in BF (and in other breeding losses were lower than in other habitat temperate areas of Europe), despite the fact that types (Wesołowski 1985; Piotrowska & the two forest types are composed largely of the Wesołowski 1989; Wesołowski & Stawarczyk same tree species and inhabited by the same

188 British Birds 98 • April 2005 • 174-193 The avifauna of Białowie˙za Forest

Table 1. Major postulated differences between primeval and secondary temperate forests (from Wesołowski 2003).

Primeval Secondary Forest size Large, continuous Fragmented, isolated Predator diversity High Low Availability of holes Abundant Shortage Species richness High Low Production of young Low High Density Low High Interspecific competition Insignificant Important bird species (Tomiałojć et al. 1984; Tomiałojć & erly evaluated without reference to a pristine Wesołowski 1990, 2004; Tomiałojć 2000; table situation; consequently, BNP is not a living 1). The main differences stem from human museum, but a dynamic natural system. If we interference or adaptation, being a combination wish to understand the past and future evolu- of: (i) fragmentation, (ii) simplification of tion of European forests, and if we want to forest structure, and/or (iii) predator extermi- properly restore a part of Europe’s natural her- nation. Human influence has also led to the itage, BF must be preserved. extinction of sensitive (e.g. large, specialised) species from managed forests, and thus to Białowieza˙ Forest – will it survive? declining species richness. By the same token, The data presented so far may have implied that this has also permitted more productive popu- the whole BF remains in a primeval state, but lations of surviving species in managed stands, this is sadly not so. Only about 13% is free from with populations sometimes increasing to levels any management, where natural processes can where limitation by resources and interspecific operate without human intervention. In other competition probably becomes significant areas, including nature reserves and large sec- (Tomiałojć 1980, Wesołowski 1983). The high tions of the national park, managers are per- productivity and high bird densities in sec- mitted to interrupt natural ecological processes. ondary woodland seem to be characteristic of What has been the impact of humans on BF all habitats where predator pressure is reduced and its avifauna? We know that humans had (e.g. islands, some human settlements) and are penetrated BF by the Neolithic era, but perma- not unique to temperate-forest bird commu- nent colonisation began in the fifteenth century, nities. after it became a royal hunting estate. It served this function until the First World War, after The conservation value of Białowieza˙ Forest which intensive timber exploitation began. Our data show the immense value of BF both Between the fifteenth and nineteenth centuries, for bird conservation and as a reference point the area of BF was reduced slightly, as some for other biological and forestry research, at open meadows and villages surrounded by both community and ecosystem levels. Studies arable fields were established inside the for- of other groups (Jędrzejewska & Jędrzejewski merly unbroken forest tract (fig. 1). Nonethe- 1998; Gutowski & Jaroszewicz 2001; Faliński less, with the exception of some fairly 2002) also highlight BF as an exceptional biodi- small-scale deforestation, direct human impact versity hot-spot; it supports approximately 990 on the remaining forest stands was limited species of vascular plants, 200 species of (Faliński 1968; Tomiałojć & Wesołowski 2004). mosses, 400 species of lichens, well over 3,000 Only the last 90 years of commercial logging species of fungi, over 9,280 species of , have resulted in large-scale habitat changes. and 58 species of mammals, including Wisent During this time, forestry operations have Bison bonasus, the largest terrestrial European affected the whole BF (except BNP), resulting in mammal. Especially important are the thou- a number of changes in its structure, not all of sands of species of micro-organisms, plants, which are completely independent: (1) the invertebrates and vertebrates dependent on appearance of new habitats – clear-cuts and decaying timber. Any plant and commu- young plantations are qualitatively different nities in secondary woodland cannot be prop- from tree-fall gaps (Fuller 2000); (2) ‘rejuvena-

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At the level of the whole local avi- fauna, the overall effect of human trans- formation of BF is a conspicuous increase in the number of bird species. The breeding species native to the forest, i.e. the ones that could have bred in BF 200-400 years ago, before the first agri- cultural clearings and human settlements started to appear, once amounted to 135- 140 species, 111 of which were forest and forest-edge species (Tomiałojć & Wesołowski 2004). The remaining ones occurred in fen marshes within the forest. Creation of new habitats allowed the colonisation of BF by an additional c. 40 non-forest species, bringing the total number of breeders to 178, and the total number of recorded species to 251 (Tomiałojć 2001; box 1). Yet BF still retains most of its original avifauna; only 4-6 species ceased to breed during the second half of the twentieth century, and only one of them – Peregrine Falcon Falco peregrinus – was a true forest inhabitant. However, several other species are currently on the verge of local extinction. Capercaillie Tetrao urogallus has already vanished from the Polish part of the forest (Wesołowski et al. 2003), while the numbers of 21 other species remain below 20 breeding pairs each (Tomiałojć 1995) and populations of

Reston Kilgour old-growth specialists, such as White- 103. In many parts of Europe, the numbers of Eurasian backed Woodpecker Dendrocopos Nuthatches Sitta europaea are affected by autumn seed leucotos, are markedly reduced. If current supplies, often in conjunction with winter weather conditions. trends continue, we may anticipate more In Białowieza˙ Forest, this relationship is much less apparent, perhaps because of the diversity of tree species, which local extinctions in the near future. reduces the dependency on one or two key species. Taking tree-covered areas alone, the extensive habitat transformations tion’ – over 70% of primeval old-growth stands affected the distribution and numbers of birds have disappeared; (3) ‘coniferisation’ – wide- in a diverse fashion. There are some winners, spread planting of conifers has resulted in a such as those species requiring open or 65% reduction of the area formerly occupied by open/low vegetation (e.g. Yellowhammer oak-hornbeam stands; (4) spatial unification – Emberiza citrinella, Lesser Whitethroat Sylvia a fine-grained mosaic of diversified species/age- curruca, Red-backed Shrike Lanius collurio), or groups has been replaced by blocks of even- dense thickets (e.g. Willow Warbler Phylloscopus aged monocultures (Bobiec et al. 2000); (5) a trochilus), which in primeval forest are confined severe reduction of the amount of dead to the edges (Wesołowski et al. 2003). Others, wood/fallen trees owing to ‘sanitary cuttings’ – a like Hazel Grouse Bonasa bonasia and Chiff- five-fold reduction in the number of large dead chaff, breed in higher densities in the managed trees and an almost 100-fold reduction of the forest (Piotrowska & Wesołowski 1989; dead-wood volume (Bobiec 2002; Walankiewicz Wesołowski et al. 2003). There are losers as well; et al. 2002) and; (6) insularisation of the once these are specialists dependent on resources continuous old-growth forest tract. abundant only in the old-growth forest and

190 British Birds 98 • April 2005 • 174-193 The avifauna of Białowie˙za Forest which struggle to exist in habitats created by continue logging at a rate of approximately forestry operations, e.g. secondary hole-nesters 150,000 m3/yr (management plans accepted in and some woodpeckers. The distribution and 2003, to be in force until 2011). As plantation numbers of White-backed Woodpecker, a areas are still too young, logging will be concen- species dependent on dead deciduous wood, trated in the old-growth patches of natural have been severely restricted in managed areas, origin (still covering about 20% of BF outside by c. 65-75% of the presumed pre-management BNP). Even the existing nature reserves are not level (Wesołowski 1995). Outside BNP, numbers excluded from logging. The result will be a con- of Three-toed Woodpeckers Picoides tridactylus, tinued loss of the natural forest remnants, while a species dependent on dying and dead spruces, the remaining old-growth patches outside the may have been reduced even more (Wesołowski strictly protected core area will be gone within et al. 2003, unpubl. data). The removal of the next decade. almost three-quarters of former old-growth This grim scenario need not, however, stands from managed areas (see above) has become a reality. If the Polish Government can inevitably had a detrimental impact on the be convinced that protection of this forest tract numbers and distribution of secondary hole- as a whole (a mere 0.6% of the entire country’s nesters, but we have no quantitative data to woodland), with preservation of its unique prove it. Such birds are critically dependent on natural heritage for future generations, is the the retention of old-growth stands, but these only acceptable solution, far exceeding the are exactly the fragments on which recent short-term benefits from timber extraction, logging operations are concentrated. If these then there would be some brighter prospects for operations continue, these species will vanish the BF and its birds. Support from birdwatchers from the managed part, and only a remnant and conservationists in the West in our struggle population, with poor prospects for long-term to preserve this unique forest is vital, not least persistence, would survive in BNP. This area is in communicating the importance of the forest too small to preserve features of the primeval to EU decision-makers. Another way of sup- forest on a scale sufficient to safeguard the con- porting BF is to visit the area, since ecotourists tinued operation of natural ecological and evo- will help to convince local people that switching lutionary processes. It is too small to harbour from logging to providing tourist facilities substantial populations of the majority of forest would be more profitable. Visit BF in the birds; the numbers of over 70% of species in breeding season and you will not only see this extended BNP remain still below 100 breeding magnificent habitat at its best and numerous pairs (Wesołowski et al. 2003). bird species absent from west European forests Scandalously, the importance of preserving (see box 1), but also, with a little luck, Wild the whole BF as a national park is not recog- Boar, Wisent, Eurasian Beaver Castor fiber, Elk nised by the authorities. Against all the evi- Alces alces, Wolf or Lynx in their natural dence, and legal obligations, they plan to environment.

Box 2. Visiting the Forest BiałowieŻa is situated 190 km east of Warsaw, and is easily accessible by car, via Siedlce and Hajnówka, a township on the outskirts of BF (fig. 1). One can also travel to the area by train from Warsaw to Hajnówka, changing at Siedlce. Convenient tourist facilities are available at the BiałowieŻa village (the closest settlement to BNP), where there are hotels of a good standard (for example, Hotel Bialovieski, tel: ++48856812022, and Hotel Zubrowka, tel: ++48856812303; see also: www.bialowieza.org.pl), as well as cheaper private rooms (contact the PTTK tourist organisation: www.pttk.bialowieza.pl or tel: ++48856812295). There are several places where traditional hunters’ food is served, which may include venison, wild boar, elk/moose and even bison (when some weak individuals are eliminated, legally, from the herd). English-speaking guides, specialising in nature- or birdwatching-tours may be hired, while bicycles for rent or horse-driven wagons are available as well. Facilities are also available at Narewka village, in the north, close to Siemianówka dam reser- voir. To enter the strictly protected reserve, it is necessary to obtain a permit or to be accompanied by a local guide; contact the BiałowieŻa National Park administration (www.bpn.com.pl, e-mail: [email protected], tel: ++48856812901).

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Acknowledgments Jędrzejewski,W., Szymura,A., & Jędrzejewska, B. 1994a. This review is based on the work of over 50 people who Reproduction and food of the Buzzard Buteo buteo in have participated in the Białowieza˙ Forest bird studies relation to the abundance of rodents and birds in during the last 29 years.We are extremely grateful to all Białowieza˙ Nat. Park, Poland. Ethol. Ecol. & Evol. 6: 179- of them, but particularly to our colleagues from the 190. census team: D. Czeszczewik, C. Mitrus, P. Rowiński and —, Jędrzejewska, B., Zub, K., Ruprecht,A. L., & W.Walankiewicz, as well as to Rob Fuller, from the BTO. Bystrowski, C. 1994b. Resource use by Tawny Owls At various stages, the project has been supported finan- Strix aluco in relation to rodent fluctuations in cially by Polish institutions, including the Polish Academy Białowieza˙ National Park, Poland. J.Avian Biol. 25: 308- of Sciences, the Ministries of Education and Environ- 318. ment, State Committee on Scientific Research, and the Karcov, G. 1903. [Białowieza˙ Forest.] A. F.Marks, St Białowieza˙ National Park. Last but not least, our deep Petersburg. (In Russian) gratitude goes to Swiss colleagues from ALA, Schweiz- Karpiński, J. J. 1935. Contributions to avifauna of erische Vogelwarte and Basler Stiftung für biologische Białowieza˙ National Park. Pr. Inst. Bad. Leśn.A 9: 1-14 Forschung, who helped financially during the critical (In Polish). years. Kowalski, M. 1992. Ecological succession in Polish forests. Folia Forestalia Polonica Ser.A (Forestry) 34: 5-18. MacArthur, R. H. 1972. Geographical ecology: patterns in the References distribution of species. Harper & Row, New York. Angelstam, P.,Anufriev,V., Balciauskas, L., Blagovidov,A., Newton, I. 1998. Population Limitation in Birds.Academic Borgergard, S., Hodge, S., Majewski, P., Ponomorenko, Press, London. 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(eds.), Advances in Vertebrate Pest Management: Holmes, R.T., Sherry,T.W.,& Sturges, F.W.1986. Bird 205-218. Filander Verlag, Fürth. community dynamics in a temperate deciduous forest: — 2000.An East-West gradient in the breeding long-term trends in Hubbard Brook. Ecol. Monogr. 56: distribution and species richness of the European 201-220. woodland avifauna. Acta Ornithol. 35: 3-17. Jędrzejewska, B., & Jędrzejewski,W.1998. Predation in — 2001. Ptaki. [Aves]. In: Gutowski, J., & Jaroszewicz, B. Vertebrate Communities: the Białowieza˙ Primeval Forest as (eds.), Catalogue of the fauna of Białowieza˙ Primeval a case study. Springer, Berlin/Heidelberg. Forest: 315-325. IBL,Warszawa.

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— & Stawarczyk,T.2003. [The Avifauna of Poland: temperate forest (Białowieza˙ National Park, Poland). distribution, numbers and trends.] PTPP ‘pro Natura’, Acta Ornithol. 25 (3): 321-351. Wrocław. — 1994.Variation in the numbers of resident birds in a — & Wesołowski,T.1990. Bird communities of the primeval temperate forest: are winter weather, seed primeval temperate forest of Białowieza,˙ Poland. In: crop, caterpillars and interspecific competition Keast,A. (ed.), Biogeography and Ecology of Forest Bird involved? In: Hagemeijer, E. J. M., & Verstrael,T.J. (eds.), Communities: 141-165. SPD Academic Publishing,The Bird numbers 1992: distribution, monitoring and Hague. ecological aspects. Proc. 12 Intern. Conf. of IBCC and — & — 1994. [The stability of the bird community in a EOC. Statistics Netherlands and SOVON 1: 203-211. temperate primeval forest: 15-year data from the — 1995. Birds from a primeval temperate forest hardly Białowieza˙ National Park.] Orn. Beobachter 91: 73-110. use feeders in winter. Ornis Fenn. 72: 132-134. (In German, English summary) — 1996. Natural nest sites of Marsh Tit (Parus palustris) — & — 1996. Structure of primeval forest bird in a primeval forest (Białowieza˙ National Park, community during 1970s and 1990s (Białowieza˙ Poland). Vogelwarte 38: 235-249. National Park, Poland). Acta Ornithol. 31: 133-154. — 2001. Ground checks – an efficient and reliable — & — 2004. Diversity of the Białowieza˙ Forest avifauna method to monitor the fate of holes. Ornis Fenn. 78: in space and time. J. Orn. 145: 81-92. 193-197. —,Walankiewicz,W., & Wesołowski,T.1977. Methods — 2002.Antipredator adaptations in nesting Marsh Tits and preliminary results of the bird census work in I: the role of nest site security. Ibis 144: 593-601. primeval forest of Białowieza˙ National Park. Polish — 2003. Bird community dynamics in a primeval forest – Ecol. Studies 3: 215-223. is interspecific competition important? 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Acta Ornithol. 22: 1-22. breeding population size of the Collared Flycatcher — & — 1995. Ornithologische Untersuchungen im Ficedula albicollis in the Białowieza˙ National Park (NE Urwald von Białowieza˙ – eine Übersicht. Orn. Beob. 92: Poland). Acta Ornithol. 37: 91-106. 111-146. —, Czeszczewik, D., Mitrus, C., & Szymura,A. 1997. How — & — 1997. Breeding bird dynamics in a primeval do territory mapping techniques reflect yearly temperate forest: long-term trends in Białowieza˙ fluctuations in Collared Flycatcher Ficedula albicollis National Park (Poland). Ecography 20: 432-453. numbers? Acta Ornithol. 32: 201-207. —, — & Stawarczyk,T.1987.Why are there low numbers —, —, — & Bida, E. 2002. Snag importance for of Parus major in Białowieza˙ Forest – removal woodpeckers in deciduous stands of the Białowieza˙ experiments. Acta Ornithol. 23: 303-316. Forest. Notatki Ornit. 43: 61-71. —, Czeszczewik, D., Rowiński, P., & Walankiewicz,W. Wesołowski ,T.1981. Population restoration after 2002a. Nest soaking in natural holes – a serious cause removal of Wrens (Troglodytes troglodytes) breeding in of breeding failure? Ornis Fenn. 79: 132-138. primeval forest. J.Anim. Ecol. 50: 809-814. —, —, Mitrus, C., & Rowiński, P.2003. Birds of the — 1983.The breeding ecology and behaviour of Wrens Białowieza˙ National Park. Notatki Ornit. 44:1-31. Troglodytes troglodytes living under primeval and —,Tomiałojć, L., Mitrus, C., Rowiński, P., & Czeszczewik, secondary conditions. Ibis 125: 499-515. D. 2002b. Breeding bird community of a primeval — 1985.The breeding ecology of the Wood Warbler temperate forest (Białowieza˙ National Park, Poland) Phylloscopus sibilatrix in primeval forest. Ornis Scand. 16: at the end of XXth century. Acta Ornithol. 37: 27-45. 49-60. Zalewski,A., Jędrzejewski,W., & Jędrzejewska, B. 1995. — 1987. Polygyny in three temperate forest passerines Pine Marten home ranges, numbers and predation on (with critical re-evaluation of hypotheses for the vertebrates in a deciduous forest (Białowieza˙ National evolution of polygyny). Acta Ornithol. 23: 273-302. Park, Poland). Ann. Zool. Fenn. 32: 131-144. — 1989. Nest-sites of hole-nesters in a primeval

Prof. L. Tomiałojć, Natural History Museum and Prof. T. Wesołowski, Dept. of Avian Ecology, University of Wrocław, Sienkiewicza 21, 50-335 Poland

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