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.

Passerines In northern areas few species are abundant. Most other species are uncommon. This is due to low diversity of landscapes and vegetation types. Uniform habitats with few plant species prevail there. For some bird species, these habitats are the optimal ones, and they reach high population density. Other species are rare, occur locally and only in some habitats. This general rule is very obvious in the forest ecosystems o f Pasvik where Willow Warbler, Brambling, Common Redpoll, Redwing and in some years Common Redstart dominate. Occurrence o f these species reaches six pairs per 1 km transect. In most other species this parameter is below one pair per 1 km transect. Breeding density of abundant passerine species did not change much between the years. In 1998—2007, the numbers o f Willow Warblers were slightly decreasing, and those o f Bramblings slightly increasing (Fig. 1.6). This could be accounted for by lum ­ bering having stopped at that time, and a new forest having started growing in that area. As Bramblings prefer to breed in mature pine forests and to forage on trees with well developed crowns, maturation of forest in the former clearings increased the area of suitable habitats and thus population growth in this species. However, for the Willow Warbler such habitats become less suitable. This bird prefers to breed in the forests with a high proportion of birch. Secondary birch forests in the old clearings are gradually replaced by pines. The decreasing area of pure birch forests and increasing proportion o f mixed and coniferous forest cause a population decline in the Willow Warbler. The numbers of Common Redpolls, Common Redstarts and Redwings remained stable (Fig. 1.6). Years —0— Willow Warbler —■— Brambling —0— Common Redpoll —*— Redwing —a— Eurasian Redstart Figure 1.6. Long-term dynamics of numbers of common species of passerines in the forests of Pasvik. 63