Factors affecting predation by buzzards Buteo buteo on released pheasants Phasianus colchicus. Kenward, R. E., Hall, D. G., Walls, S. S., Hodder, K. H. 2001. Journal of Applied Ecology, 38(4): 813-822. 1. Location data from 136 radio-tagged common buzzards and prey remains from 40 nest areas were used, with vegetation surveys and records from 10 gamekeepers, to investigate raptor predation at 28 pens where ring-necked pheasants were released in southern England. 2. Among 20 725 pheasant poults released in 1994-95, keepers attributed deaths of 4.3% to buzzards, 0.7% to owls, 0.6% to sparrowhawks, 3.2% to foxes and 0.5% to other mammals. 3. Fresh pheasant remains were found in 7% of 91 visits to buzzard nests, and 8% of radio-tagged buzzards were relatively strongly associated with pheasant pens. 4. Predation by buzzards was recorded most often at release pens with little shrub cover, canopy that was deciduous and many released pheasants. Predation was worst in large pens with much ground cover and low pheasant density. 5. Radio-tagged buzzards were located most often at pens with open, deciduous canopy. Pens were most likely to be visited by buzzards that fledged nearby, but proximity of buzzard nests had relatively little influence on the level of predation. 6. In order to understand how predation is influenced by prey vulnerability, predator learning or predator and prey abundance, we recommend parallel study of predators and prey.