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.

Phylloscopus Phylloscopus Phylloscopus trochitus collibita borealis Figure 3.10. Spatial distribution o f the three Phylloscopus warbler species. The dashed line shows the foraging areas o f the birds. Figure 3.11. Succession and frequency of foraging manoeuvres o f Chiffchaffs. P - pick; H — hop; F — flight; HF — hovering flight; S — searching for prey; N (S) is the num ber 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 direc­ tion o f hops and flights. N(S) = 77 (1199) dense vegetation with well developed layers of branches and leaves. Such crown structure develops under the conditions o f sufficient but mainly vertical illumina­ tion and fits the peculiarities o f Chiffchaff foraging behaviour (Fig. 3.10, Khlebosolov et al. 2003). The main specific features o f the Chiffchaffs foraging behaviour is that when feeding, it mainly moves horizontally and makes shorts hops or flights (Fig. 3.11). Sometimes Chiffchaffs pick insects at the tips o f twigs in hovering flight, but this foraging manoeuvre is not typical o f this species (Khlebosolov et al. 2003). Arctic Warblers prefer habitats where bushes and trees form dense shrub, their trunks are located close to one another and the branches mainly grow vertically (Fig. 3.10). Such habitats occur in Pasvik in the stands o f willows, alder, young birches along the shores o f some rivers and lakes, along roads and cuttings, and in the crooked birch forest. 129