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.

The numbers o f some other passerines are locally high. For example, occurrence o f the Sedge Warblers in coastal shrubs may reach 16 pairs • km 1o f transect, occurrence of Yellow Wagtail on the edges o f swamps and on swampy lake coasts may reach 14 p a irs* km 1 o f transect, occurrence o f Bluethroats in wet shrubs may be up to 4.5 pairs • km-1of transect, occurrence o f Meadow Pipits in the mountain tundra may reach 3 pairs • km-1o f transect. However, as the occurrence o f such habitats is limited, the total number o f these species is low. Some avian species do not breed in Pasvik annually. For instance, Sedge Warbler in some years is one o f the most common species here, whereas in other it is missing altogether. The reason is apparently that many bird species are at the limit o f their breeding range in the study area. When the total numbers decline, breeding range bor­ ders are shifted towards the optimum zone, peripheral populations shift towards the core area, and no breeding occurs in the pessimum zone. In the recent years, range expansion and colonization o f the new habitats is recorded by southern species o f birds which had not bred in Pasvik earlier or occurred only in anthropogenic habitats. In 1998, the Greenfinch was first recorded in human settlements. Since 2001. this species regularly occurs in villages and adjacent forests. In 2003, breeding o f the Siskin was recorded for the first time. In 1996 and in 2003—2004, singing European Robin males were recorded, and in 2005—2006, flocks o f Long-tailed Tits were encountered. In 2001 and 2003, Little Bunting has been recorded, and in 2004, breeding was confirmed. In optimal habitats, occurrence of the Little Bunting is at 6 pairs • km '1o f transect. In 2006, breeding of the Lesser Spotted Woodpecker was confirmed. In 2007, a singing Yellowhammer male was first observed. Until 2002, Great Tits only bred in the vicinity o f human settlements. Since 2003, it was regularly recorded in birch forests along the roads, cuttings and power lines. In 2005-2006, breeding o f the Great Tit was recorded in mixed pine and birch forests, and in 2007 a pair breeding in the pine forest was found. The numbers o f Pied Flycatchers gradually grow, and the birds colonise new habitats. A broad infiltration of southern bird species in the ecosystems o f Pasvik may be related to the global climate warming that shifts the borders o f birds’ breeding ranges towards more northern areas. The study o f the factors that govern long-term dynam ics o f avian numbers is important for understanding o f the organisation o f northern communities and claims close attention on the part of ornithologists. 64