Diet and ecology of Short-eared Owls Asio flammeus breeding on heather moor

Observations were made of the diet and breeding biology of a small population of Short-eared Owls Asio flammeus breeding on a Welsh heather moor during 1971–¸84. Of 694 vertebrate prey items, Pigmy Shrews Sorex minutus were dominant numerically (43% of prey), Wood Mice Apodemus in biomass (18%). Significant numbers of Common Shrews Sorex araneus, birds, Short-tailed Voles Microtus agrestis and Bank Voles Clethrionomys glareolus were noted. Proportions of prey species in diets varied between. sites, probably in relation to differences in vegetation between hunting ranges. The birds were generally inconspicuous and their population density was low; numbers, time of breeding, clutch-size, and breeding success were fairly uniform. This breeding ecology is contrasted with that reported for Shorteared Owls breeding in grassland and feeding on Microtus voles.