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.

s N ( S ) = 68(2081) Figure 3.12. Succession and frequency o f foraging manoeuvres o f Arctic Warblers. P — pick; H —hop; F —flight; HF —hovering flight; FT —take-off —pick —landing; S —searching for prey; N (S) is the number o f successions, in parenthesis, the overall observation time (s). Numbers show the frequency o f foraging manoeuvres after the preceding ones, arrows show the direction o f hops and flights. Selection o f these habitats is governed by the Arctic Warbler’s foraging behav­ iour. When foraging, the birds move vertically mostly along the boughs in the inner and middle parts o f the crown. Most picks are made after a series o f upward hops, less often after a series o f horizontal or downward hops. Often the bird looks for prey during 1—3 s before a pick (Fig. 3.12, Khlebosolov 1995). The structure o f the ecological niche and the pattern o f ecological relation­ ships o f the Willow and Arctic Warblers and Chiffchaff are governed by the foraging behaviour and structure of the preferred microhabitats. The difference in foraging behaviour o f these three species mainly concerns the direction o f hops and flights. Willow Warblers move in varying directions when foraging. Chiffchaffs mainly use horizontal movements, and Arctic Warblers move vertically. On the basis o f species- specific behavioural stereotypes, the birds select characteristic microhabitats. Willow Warblers prefer crowns o f trees and bushes where branches and leaves grow in different directions and form no horizontal or vertical layers. Chiffchaffs forage in places with pronounced horizontal layers o f vegetation. Arctic Warblers, on the contrary, select habitats where trees and bushes grow closely and their trunks and branches are vertically oriented. Features o f foraging behaviour and the structure o f preferred microhabitats govern the pattern o f spatial distribution o f Phylloscopus warblers in the forest ecosystems of Pasvik.