The birds of Pasvik / E. I. Khlebosolov, O. A. Makarova, O. A. Khlebosolova [et al. ; English transl. Nikita Chernetsov]. - Ryazan : Golosgubernii, 2007. - 175 с. : ил., портр.

228. Lapland Longspur Calcarius lapponicus (L innaeus, 1758). U ncomm on breeding species o f lowland tundra. 229. Snow Bunting Plectrophenax nivalis (L innaeus, 1758). Comm on migrant and uncommon breeding species o f mountain tund ra and rocky patches. 1.3. Long-term dynamics of bird numbers A typical feature o f northern ecosystems is p ronounced seasonal and annual fluctuations o f bird numbers caused by various ecological factors. Changing bird numbers may follow climate change, result from inner population processes o r from adaptation o f birds to living in relatively homogenous and poor no rthern comm un i­ ties formed in cold climate. We have long-term data on numbers dynam ics for waterfowl, grouse, waders, and passerines. They allow us to identify the typical features o f fauna form ation and community organisation in the birds o f Pasvik. The analysis is based on our data and the materials o f other authors published in Annals o f N ature o f Pasvik nature reserve (1997, 1998a, 1998b, 1999, 2000, 2001, 2003b, 2003b, 2005a, 2005b), and in the reports o f Norwegian ornithologists (Thingstad, 1995; Thingstad et al., 1997, 2000; Gunther, Thingstad, 2002; Gunther, 2006). Waterfowl The results o f annual waterfowl surveys on Pasvik river in 1996-2005 are given in Table 1.1. Numbers o f common species as the B lack-throated and R ed-throated Divers, Whooper Swan, Eurasian Wigeon, Eurasian Teal, M allard, Pintail, Tufted Duck, Black Scoter, Common Goldeneye, Snew, Red-breasted and C omm on Mergansers generally remains stable between the years. Significant annual variation o f numbers is typical o f the Bean Goose and the Velvet Scoter. G re a ter C o rm o ran t, Gadwall, Garganey, Shoveler, G reater Scaup, Long-tailed Duck do no t occu r annually. These birds are probably vagrants incidentally recorded during th e ir seasonal movements. Some o f them may breed in Pasvik, and under favourable ecological conditions even colonise a new area. 58