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.

N. V. Zuev The Birch forest is the optimal habitat for the Willow Warbler. succession stages birch forests also occur in the clearings. Later they are replaced by pine and birch or pine forests, more typical of these conditions (Belov & Baranovskaya 1969, Tsvetkov & Semenov 1985). During these succession changes o f the forest structure Willow Warbler numbers gradually decrease. Birch trees occur in different proportions in various types o f pine and birch forest that grow by patches o f varying size on more fertile soils in the lower parts o f the slopes, in depressions and in flat areas. The breeding density of the Willow Warbler changes in relation to the proportion o f birch in pine stands (Fig. 3.1, types 5—6). Statistical analysis shows a positive correlation between Willow Warbler num ­ bers and the volume o f crowns (r = 0.78) and numbers of tall birch trees per unit area (r = 0,66) and a negative relationship with the same parameters of pines (r = -0,76 and -0,61, respectively; Tab. 3.1, Fig. 3.2). Table 3.1. Relationship between the numbers o f Willow Warblers and Bramblings with differ­ ent biological characteristics o f the forest. Pairwise correlations Bird species Pine Birch Pine Birch Pine Birch Crown volume, Tree height in the Number of tall trees m ' • ITT first story, 111 per 500 m2 Willow Warbler -0 ,7 7 0,78 -0 ,6 7 -0 ,0 4 -0 ,6 2 0,66 Brambling 0,38 —0,17 0,39 0,41 0,58 0,37 119