Diet diversity of the Common Buzzard (Buteo buteo) in a vole-less environment

Capsule The absence of key prey, voles, in Ireland, is associated with wide dietary niche in a top predator, the Common Buzzard (Buteo buteo). Aims To examine the diet of the Buzzard as it recolonizes Ireland from the north and where prey diversity is low, prior to the presence of two small mammal species, the Bank Vole Myodes glareolus and Greater White-toothed Shrew Crocidura russula, which are invading from the south of Ireland. Methods Pellets and prey remains were collected in and around Buzzard nests during the breeding season in 2008, 2010 and 2011 in the northeast of Ireland and productivity at each site was recorded. Diet was analysed in terms of frequency and biomass of prey to calculate dietary niche width and the importance of each prey type in the diet, and the relationship between the number of fledglings produced and the proportion of prey items in the diet was tested. Results A total of 1194 items were identified at 61 nests over the 3 years. The diet of Buzzards in Ireland consists mainly of rabbits, rats and medium-sized birds, particularly corvids. Dietary niche breadth is wide and the population comprises mostly generalist individuals. The proportion of rabbit in the diet had a significant positive effect on the number of fledglings produced in all years. Conclusion The Buzzard in Ireland has adapted to the lack of vole species by adopting a wide dietary niche; however, rabbits remain an important component of the diet influencing productivity in the area. A wide dietary niche may promote the high rate of spread of the growing Buzzard population. Although rabbits are consumed widely by Buzzards in Ireland, they are not obligatory rabbit specialists, with corvids, medium-sized birds and rats being important components of their diet. Should Buzzards also incorporate invasive mammals into their diet, such that they meet their energy needs solely from mammal prey, there is the potential for change in prey community structure, particularly with regard to avian species.