TERRITORIALITY AND HABITAT USE OF COMMON BUZZARDS (BUTEO BUTEO) DURING LATE AUTUMN IN NORTHERN GERMANY

We studied habitat use and spatial distribution of Common Buzzards (Buteo buteo) in Schleswig-Holstein, northern Germany during the autumn of 2000, to assess the raptors' territoriality and its consequences for their use of space. For this purpose, we performed point counts covering an area of 20 km(2) during each of 20 continuous days and recorded 1537 observations of Common Buzzards and 109 of Rough-legged Hawks (Boles logopus). Applying multivariate Poisson regression combined with randomization tests, we detected that Common Buzzards showed a preference for areas with a larger distance from nesting sites of the previous spring (P = 0.019; n = 290 grid units of 250 X 250 m in all three cases), a high density of vole holes (P <0.001), and a low density of perch-sites (P = 0.005). These preferences regarding vole holes and perches were also valid when only grid units far from the nesting sites were considered. Indirectly, the buzzards were also affected by the amount of grassland and by the amount of dry land, as these parameters were strongly related to vole-hole density. The distributions of the sympatric wintering species Rough-legged Hawk and Common Buzzard did not affect each other. Our study indicated that territorial sedentary, breeding pairs displaced nonbreeders and wintering birds into suboptimal habitats, and it offers valuable clues on the constraints for Common Buzzards in areas where they occur in high abundance during late autumn and winter.