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.

Н - 0 . 5 0 - Н 0,30 0 ,3 0 ' H f - 0,40- H t - 0,20—p —0,20—H- " 0,20 10/ ^ H t FP HF N(S) = 52 (2606) Figure 3.5. Succession and frequency o f for­ aging manoeuvres o f Bramblings: P — pick, H — hop, F — flight, FP — flight — pick — landing, HF —hovering flight, S —searching, N (S) —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. Figure 3.6. Structure o f tree crowns preferred by Bramblings. The dashed line shows the for­ aging zone o f Bramblings in the crown. they do not o c c u r there a ltogether (Fig. 3.1). Th e b reeding density of Bramblings increases with the age o f the forest. However, this species is sen ­ sitive to stand density: its density is lower in sparser stands (Fig. 3.1, 3.2). The reason is apparently that a home range must include a certain number o f trees. In sparse forests home range size has to be larger, so that breeding densi­ ty drops. This is most obvious in old pine stands where, all other condition being equal, the decreasing number o f trees per unit area causes a significant decrease in breeding density (Fig. 3.1, type 8). The op tima l habitats o f Bramblings are defined not by the spe­ cific composition o f trees, but by vege­ tation struc tu re . In no rth e rn Scandinavia these birds inhabit not only pine and mixed forests but m o u n ­ tain birch forests as well (Hogstad 1975, Ange ll-Ja cob sen 1980, Jarv inen & Rajasarkka 1992), where they prefer patches o f tall tress and well developed crowns and no u nd e rs to ry (Angell- Jacobsen 1980). In no rthwe ste rn Karelia the main Brambling habitat is sparse pine forest. In Northeastern Asia Bramblings b re ed in high riparian pop la r forests. Tree crows in such forests are loose and spreading and suit­ able for fo raging (Khlebo so lov & Zakharov 1997). Probably the crown structure and density are the key factors that govern the habitat distribution and 124