Habitat and weather requirements of diurnal raptors wintering in river valleys

The winter raptor community was studied in river valleys of North Eastern Poland during the winters of 2000–2010. Via transect counts method we showed the potential drivers of raptor abundance, and co-occurrence patterns. We analysed the influence of weather and habitat factors along on the single species abundance and diversity of the raptor assemblage. We found that higher temperatures corresponded with higher occurrence of the common buzzard Buteo buteo, rough-legged buzzard Buteo lagopus, Eurasian sparrowhawk Accipiter nisus, hen harrier Circus cyaneus and lower of the common kestrel Falco tinnunculus. When considering the effect of each habitat variable on the whole raptor assemblage, the relative proportion of urban areas to pasture had the most distinct effect on species abundance and diversity. Most of species were found to be less abundant in areas with a high proportion of urban areas, while some, like the Eurasian sparrowhawk and the northern goshawk Accipiter gentilis, occurred more often on such areas. We observed that the difference in the number of these species could be explained mainly by the different habitat requirements due to individual food preferences and flexibility of migration strategies.