Winter diet of Common Buzzards Buteo buteo on a Scottish grouse moor

Abstract

The winter diet of Common Buzzards Buteo buteo on a Red Grouse Lagopus lagopus scotica moor was dominated by small mammals, whilst grouse were a minor prey item.
Aims: To assess winter diet of Common Buzzards from pellets collected at roost sites on and around a managed Red Grouse moor, and to explore temporal, spatial and age-related variation in diet composition.
Methods: Forty-four winter roost sites were located during two winters using a combination of observations from vantage points and individual Common Buzzards equipped with either radio or satellite transmitters. Pellets were collected between October and March each winter and analysed to assess dietary composition.
Results: Small mammals were the main prey in both years, comprising 60–67% of items and occurring in 88–92% of pellets. Diet varied between years, with more lagomorphs and birds (passerines, corvids and pigeons) but fewer Red Grouse eaten when grouse abundance declined. Grouse formed 1.1% and 0.6% of prey items, and occurred in 3% and 2% of pellets from each winter, respectively.
Conclusion: Common Buzzards rely on small mammal prey during winter. When available, Red Grouse are a minor dietary component, the amount of which reflects their abundance in the environment. The opportunism of Common Buzzards can result in temporal variation in winter diet.