Great black-backed gull stomach contents of great black-backed gulls was made up of birds, while a further 17% of stomach contents was made up of tern eggs alone. Adult or fledged juveniles of various bird species have also been predaceously attacked. Some fully-fledged or adult birds observed to be hunted in flight or on the ground by great black-backed gulls have included "Anas" ducks, ruddy ducks ("Oxyura jamaicensis"), buffleheads ("Bucephala albeola"), Manx shearwaters ("Puffinus puffinus"), pied-billed grebes ("Podilymbus podiceps"), common moorhens ("Gallinula chloropus"), terns, Atlantic puffins ("Fratercula arctica"), coots ("Fulica" ssp.), glossy ibises ("Plegadis falcinellus"), rock pigeons ("Columba livia") and even predatory birds
Shearwater Shearwater Shearwaters are medium-sized long-winged seabirds. There are more than 30 species of shearwaters, a few larger ones in the genus "Calonectris" and many smaller species in the genus "Puffinus". The "Procellaria" petrels and "Bulweria" were believed to belong to this group, but are only distantly related based on more recent studies, while the "Pseudobulweria" and "Lugensa" "petrels" are more closely related. The genus "Puffinus" can be divided into a group of small species close to "Calonectris" and a few larger ones more distantly related to both. These birds are most common in temperate and cold waters. They are pelagic