Rough-legged Buzzard Buteo lagopus wintering in central eastern Poland: population structure by age and sex, and the effect of weather conditions

Abstrakti

Conditions at wintering grounds affect the numbers of birds of prey to various extents. Weather may influence the latitudinal winter distribution of short-distance migrants, such as the Rough-legged Buzzard, with respect to age and sex. Inventories were conducted in central eastern Poland during 2003-2006 on a sample plot with very high densities of Rough-legged Buzzards. In particular years, Rough-legged Buzzards wintered in different numbers, but there was no significant variation in numbers among phenological periods of winter. The mean daily temperature but not the depth of snow influenced numbers so that lower daytime temperatures were associated with higher numbers of wintering Rough-legged Buzzards. The observed age and sex structures were similar to the latitudinal winter distribution of these parameters in the Rough-legged Buzzard population in the Nearctic region: adults significantly outnumbered immatures, and among adults there were more females than males.