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by the birch wood. The diversity o f forest vegetation is slightly increased due to ver­ tical zonality. A nother reason for low diversity o f birds is th e restricted am oun t or low diversity o f food resources due to harsh climate cond ition s or some o th er e co ­ logical factors. The m ountain birch forests o f the northwestern Kola Peninsula are a unique natural community. In order to understand how the ecosystems o f this landscape are formed and function, a comprehensive research in to behaviour, ecology and mutual relationships o f the local bird species is necessary. 112