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.

The diet of mergansers includes pike, perch, trout, cisco, vendace and other species o f fish. Common Merganser is larger than Red-breasted Merganser and captures larger prey (Ivanter 1975, Semenov-Tian-Shansky & Gilyazov 1991). Mergansers search for food when swimming with their head submerged. When they visually locate their prey, they dive and follow it. In deep places mergansers catch fish by diving, and in shallow places they follow it by skimming on the surface with their head submerged and wings beating in the air (C ram p & Simmons 1978, Semenov-Tian-Shansky & Gilyazov 1991, Rezanov & Rezanov 2006). It is usually assumed that the Red-breasted Merganser mainly inhabits lakes, whereas the Common Merganser breeds on rivers (Semenov-Tian-Shansky & Gilyazov 1991). In Pasvik this is only true as concerns the Common Merganser which mainly occurs on the Pasvik river. The Red-breasted Merganser breeds both on the lakes and on the river. Its numbers in the Pasvik river are maximal and reach 9.7 pairs per I km o f the shoreline. On the lakes this param eter varies between 1.1 and 4.8 pairs per 1 km shoreline (Zakoldaeva 2005). Our observations show that during foraging, the two species use different parts o f the river. Red-breasted Mergansers mainly occur in shallow places near the coast, especially in small bays and in calm sections of the river. Common Mergansers mainly forage in the middle o f the river looking for prey and making long dives (cf. Ivanter 1975). Even though the biology o f waterfowl species is well studied, their biocenotic relationships remain obscure. Therefore it is difficult to identify the methods of resource sharing and niche separation, and the mechanisms o f formation o f the specific structure o f the waterfowl community in aquatic and wetland habitats of Pasvik. 2 .4 .2 . Raptors and owls In the Pasvik valley several species o f raptors and owl occur that take various food, use different habitats and different methods o f searching for prey and forag­ ing. Depending on these factors, all birds o f prey may be divided into several eco ­ logical groups. Ecological groups of raptors Two large groups may be distinguished among the raptors o f Pasvik that differ by their body size and thus by the size o f their prey. The largest raptors are the Osprey, White-tailed Eagle, and Golden Eagle. They mainly forage on large birds, mammals, fish and inhabit different landscapes. All other raptors are smaller. This group includes the Goshawk, Sparrowhawk, Rough-legged Buzzard, Peregrine, Gyrfalcon, Merlin, and Kestrel. They take 83