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In spite of environmental uniformity of the European Plains, a conspicuous east-west gradient in the woodland avifauna and breeding bird community composition has been revealed. The species richness in the western woodland avifauna is lower by 32-36% than in the respective eastern samples (n = 120-127 species). Apart from being poorer in species, western communities tend to contain a higher proportion of species which develop dense populations. These features may result from past — mostly postglacial — natural events, from a secondary gradient in the intensity of human impact or from both of them. The data at hand provide evidence for a strong prevalence of the second factor. In view of the mostly anthropogenic character of the differences described, many west-European data can hardly be used as models of the natural patterns in studies of breeding bird ecology. New continent-wide comparative research is necessary to better control for anthropogenic bias in field data. For valid future pan-continental comparisons of bird communities a few large patches of near-pristine woodland should be preserved in the East, as well as restored in the West. Bird ecology studies need also a better co-operation with the archaeozoological and historical research to take into consideration past conditions which could also have influenced the present-day life patterns of European birds.
Woodpeckers are a very good indicators of forest naturalness. The fact that many species of these birds are in decline in central and western Europe resulted from changes in forest management (e.g. favouring coniferous forest, removal of dead trees). The aim of this research was to evaluate the importance of patches of deciduous species for the occurrence of some specialized woodpeckers in the conditions of Scots pine dominated stands. The study focused on species associated with deciduous forest, i.e. middle spotted woodpecker Leiopicus medius (L.), white−backed woodpecker Dendrocopos leucotos (Bechstein) and grey−headed woodpecker Picus canus (Gmelin). Statistical analyses were performed for the woodpeckers, which occurred in more than 10 territories. The studies were performed in 2015−2017 in the southern part of the Sandomierz Basin in three study areas (52,6−59 km²). Two plots were dominated by black alder Alnus glutinosa and oak Quercus sp., while the third one was characterized by the highest share of black alder, followed by silver birch Betula pendula and oak. Deciduous trees at the age over 80 years accounted for less than 2% of the total area of each plot. The most abundant bird species in patches of deciduous forest was the middle spotted woodpecker (25 territories), while the rarest was white−backed woodpecker (1 territory). Grey−headed woodpecker appeared in 12 territories. The density of woodpeckers in deciduous forest areas ranged from 0.45 territories/100 ha for grey−headed woodpecker to 1.54 territories/100 ha for the middle spotted woodpecker. In the alder patches we found all territories of grey−headed woodpecker, 24% territories of the middle spotted woodpecker and single territories of white−backed woodpecker. The patches dominated by oak accounted for about 76% of territories of middle spotted woodpecker. The average area of the patches with presence of middle spotted woodpecker and grey woodpecker was significantly higher than the patches where woodpeckers were absent. The middle spotted woodpecker occurred in the forest patches with the highest average age. Redundancy Analysis (RDA) demonstrated that the occurrence of middle spotted woodpecker was most strongly associated with the area of the patches over 10 ha, while the grey−headed woodpecker preferred mature forest stands of alder. These species abundance was negatively correlated with a patch area less than 10 ha.
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