[Adaptive features of the ecology and annual cycle of the willow warbler (Phylloscopus trochilus L.) at the northern boundary of the Siberian part of the range].

The ecology of the willow warbler in the north of Western Siberia is considered, and the adaptations that enable the spread of this species to the Subarctic are analyzed. It is established that one of the key factors that caused the change in the range of this species is the northward distribution of shrubs and, hence, the biomass of insects (available food items of these birds).