Living on the Edge: Juvenile Foraging and Adult Breeding Ecology of an Aerial Top Predator in Urban Environments

Urbanization is irreversibly transforming natural ecosystems globally, yet we still lack a holistic understanding of the challenges and opportunities that urban environments present to wildlife. To investigate how raptors utilize urban landscapes, we analyzed 4 years of GPS tracking data of 22 juveniles collected during natal dispersal, combined with 7 years of nest-monitoring data from an urban population of the Common Buzzard (Buteo buteo), an opportunistic rodent specialist, in Berlin (Germany). Our goals were threefold: (a) to estimate core foraging ranges (CFRs), (b) to characterize small-scale temporal foraging areas (TFAs) within these ranges, and (c) to model the breeding habitat suitability based on environmental predictors. CFRs were distributed across the city, with a mean area of 11.0 km² (±13.9 sd). TFAs within these ranges had a mean area of 0.2 km² (±0.3) and were occupied over a mean time span of 274 days (±198). TFAs were mostly located in residential open areas (e.g., courtyards) and were characterized by decreasing area and shorter occupation duration with increasing human population density. Urban TFAs showed a high prevalence of rats (Rattus norvegicus). Active pest control measures were observed at most TFAs, particularly in residential areas. We mapped a total of 17.3 km² of suitable breeding habitat within the study area (217 km²) and 45.4 km² when projected across the city region (890 km²). Suitable breeding habitat consisted of isolated patches, i.e., single courtyards in residential areas, and a network of urban green spaces, e.g., city parks and cemeteries. Cities can provide profitable foraging and breeding conditions for raptors, with abundant prey in proximity to suitable breeding sites. The study improves our understanding of how raptors utilize the urban city landscape and underlines the importance of urban green spaces as a basis for the protection and conservation of urban wildlife.