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.

ability of their foraging substrates that may be characterised by crown volume per unit area. This parameter is the highest in middle-aged pine and birch forests with the ground layer of green moss and semitrutex (Fig. 3.1, type 5) or in red bilberry pine forests (Fig. 3.1, type 8) growing on drained, well inundated soils (Tsvetkov & Semenov 1985). The trees grow there rather densely and their crowns are well developed. In lichen pine forests (Fig. 3.1, type 7), whose growing conditions are suboptimal due to dry and poor soils, stands may be quite dense but the crown vol­ ume o f individual trees is small. Therefore occurrence o f Brambling feeding sub­ strates is generally lower there than in the aforementioned forest types. In old pine and pine and birch forests (Fig. 3.1, type 9) stands are sparser, and even though the crown volume o f individual trees is increased, occurrence o f feeding substrates and thus Brambling numbers are lower. Brambling density reaches the highest values in well developed pine and mixed forests ( Fig. 3.1). This species shows a positive correlations with the crown volume o f pines (r = 0.47) and no significant correlation with the crown volume of birches (r = -0 .1 7 ; Tab. 3.1, Fig. 3.2). However, in the Brambling the relationship with habitat is less straightforward than in the Willow Warbler. First, the correlation with the volume o f pine crowns is not very strong. Second, Bramblings are quite common not only in pine and mixed forests, but in pure birch stands as well. Third, some positive rela­ tionship exists between Brambling numbers and tree height (r = 0.39 and r = 0.41, respectively) and number o f trees per unit area (r = 0.58 and r = 0.37 , respectively; Table 3 .1 , Fig. 3.2). The optimal Brambling habitats are apparently rather dense pine forests with birch admixed and tall trees with well developed crown. Such habitat selection may be explained by the peculiarities of foraging behaviour of this species. Bramblings forage by searching for prey and making hops between the b ranch ­ es. Most picks are made after a series o f horizontal or vertical hops, less frequently after short flights or hovering. After a pick the birds look for prey during 1 - 3 s (probably not directly for food but rather for a perspective direction of movement) or move further by horizontal or vertical hops (Fig. 3.5). The foraging rate of Bramblings is rather high, they constantly move by hops along and between the branches, rarely get food by reaching for it, and most often pick food just after a hop. This foraging method is efficient in loose crowns where the distance between the branches is large enough and concentration of leaves and small twigs is small. Such conditions exist in pine crowns where Bramblings often forage. The birds prefer to forage in looser inner parts o f crowns (Fig. 3.6). Therefore pine stands are the optimal habitat for this species that forages in rather loose crowns o f old tall trees ( Khlebosolov & Zakharov 1997). The crowns of young trees are too dense for foraging of Bramblings, therefore their numbers are low or 123