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.

Avifauna o f Pasvik includes several taxonom ic and ecological groups. The birds from different groups occupy basically different ecological niches and usually have no direct contacts. They inhabit certain habitats, prefer certain food and use species-specific foraging methods. Within such groups closer biocenotic links exist that perm it the existence o f interspecific competition. Comparative analysis of behaviour and ecology o f birds makes it possible to understand how specific com ­ position, numbers and spatial distribution are governed. Below we will analyse the specific structure o f the avian population o f Pasvik, including the main ecological groups. 2 .1 . The role of physical geographic factors in formation of specific structure of bird population in Pasvik Specific structure o f bird population o f Pasvik is influenced by various geo­ graphic factors. The main role is played by the cold climate, low productivity o f boreal ecosystems, and unstable conditions. The cold climate inhibits the formation o f plant communities in Pasvik. As specific diversity of birds is to a large extent governed by vegetation, poor and sim­ ple plant communities result in low diversity and numbers o f birds. Cold climate not only negatively influences vegetation structure but also decreases the produc­ tivity o f habitats. In riparian forests along the Pasvik river and in some other places in the valley well developed plant communities may form. In spite o f this, specific diversity o f birds is still much lower there than in more southern areas. In warm cli­ mate in highly productive communities the birds can specialise and use various for­ aging techniques, in cold climate and when food is scarce the birds occupy broad ecological niches and have to utilise a limited num ber o f foraging methods (Whittaker 1975). In the communities with low productivity similar habitats are occupied by a single species, whereas in rich communities several species coexist. 69