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
Calonectris Calonectris Calonectris is a genus of seabirds. The genus name comes from Ancient Greek "kalos", "good" and "nectris", "swimmer". The genus comprises three large shearwaters. There are two other shearwater genera. "Puffinus", which comprises about twenty small to medium-sized shearwaters, and "Procellaria "with another four large species. The latter are usually named as "petrels", although they are thought to be more closely related to the shearwaters than to the other petrels. The taxonomy of this group is the cause of some debate, and it is only recently that the Cape Verde shearwater has been split from Cory's shearwater. The species