On Foula, Shetland, sheep were observed biting off the legs, wings or head of unfledged young Arctic terns. Large numbers of tern chicks and a few Arctic skua chicks were found with amputations characteristic of these attacks by sheep. On Rhum, Inner Hebrides, red deer were watched biting the heads off manx shearwater chicks and occasionally also chewing the shearwaters' legs and wings to excise bone. Killing of birds and the selective ingestion of bone-rich parts by ruminants has not previously been widely documented. It is presumably a response to mineral deficiencies in the vegetation, and it may only occur in rare situations where ruminants feed on mineral-deficient vegetation on which there are dense colonies of ground-nesting birds.