Breeding success and productivity of urban and rural Eurasian sparrowhawks Accipiter nisus in Scotland

Abstract

ABSTRACTThe conversion of rural habitat into built-up areas often affects animal species negatively. However, some generalist bird species and raptors relying on avian prey have colonised urban environments. Surprisingly, no study has compared the breeding biology of urban and rural populations of a very common old-world raptor, the Eurasian sparrowhawk (Accipiter nisus). Here, we compare the territory occupancy rate, breeding success and productivity (i.e., the number of fledglings) over four years (2009–2012) of an urban and a rural sparrowhawk population in Scotland. Our results showed that urban sparrowhawk territories were occupied significantly more frequently (mean % years occupied ± se: 66.8 ± 5.9%) than rural territories (42.8 ± 4.7%). Clutch size, brood size and the number of fledglings produced did not differ between the populations. However, the breeding success was significantly higher in the urban (annual mean ± se: 97.2 ± 2.3% nests successful) than in the rural population (80.5 ± 6.6%) because of a higher nest desertion rate at the egg and chick stages in the rural population. Our study suggests that warm weather in July may have more negative effects on rural sparrowhawks compared to urban sparrowhawks. The mechanism behind the difference is unknown and requires further work.