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.

Terns (Sternidae) are m uch narrower specialised th a n gulls. T h eir prevailing foraging m ethod is search flight and swooping. Hovering before swooping for prey is very typical o f them (Yudin 1965). The only comm on breeding species o f terns in Pasvik is the A rctic Tern. This bird feeds mainly on small fish and occupies very different habitats: sea coasts, rivers, lakes, swamps. Breeding o f small numbers o f th e C omm on Tern in Pasvik canno t be ruled out. V.D. Kokhanov repeatedly recorded these birds in the Pasvik valley in the summers o f 1993 and 1994 (Annals o f N atu re... 1997). The C omm on Tern may be more common in Pasvik th an it is usually assum ed, bu t it is difficult to distinguish from the Arctic Tern in the field. Predation and cleptoparasistism are typical o f skuas (S tercorariidae). They take mice and voles, birds, take away prey from gulls, auks, gannets, co rm orants and other piscivorous birds, and predate nests, eat nestlings and scavenge (Yudin 1965). In the Pasvik valley skuas occur only during passage. However, on th e sea coast and in the lowland tund ra they are comm on. On the coast and islands in the Barents Sea, the Parasitic Skua breeds regularly. The Long-tailed Skua occurs in the low ­ land tundra. Since recently, the G reat Skua regularly breeds o n th e islands in the Barents Sea. Since 1988, nests o f this species have been regularly found on the Seven Islands archipelago (Krasnov 2003). Three o r four pairs o f G rea t Skuas annually breed on Ainovy Isles situated n e ar the m o u th o f th e Pasvik River (Tatarinkova, Chemyakin, pers. comm .; ou r data). Shorebirds and gulls play an im po rtan t role in the n atu ral ecosystem s o f Pasvik. In order to understand b etter what governs specific com po sition , num bers and habitat distribution o f these birds, how they share th e resources and separate th eir ecological niches, avoid com petition and co-exist in one area, m o re detailed stu d ­ ies o f their behaviour and ecology are necessary. Special a tte n tio n should be paid to the study o f gulls and terns, because the structure o f th e ir ecological niches and p a t­ terns o f their relationships in natu ral ecosystems are especially difficult to d e te r­ mine due to the broad range o f th e ir diets, foraging places an d techniques. 2 .4 .5 . Passerines In the comm unity o f small passerines o f Pasvik several ecological groups may be distinguished on the basis o f th e ir spatial d istribu tion , diet, and characteristics o f foraging behaviour. Most clearly defined ecological groups include forest-dwelling birds, coastal scrub and wetland birds and passerines o f th e m o u n ta in tund ra. Members o f these groups are spatially separated and do no t engage in direct com ­ petition. Species th at co-exist in sim ilar habitats or land scapes avoid com petition by using different food or foraging in different m icrohab itats whose structu re is suit- 104