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
Barolo shearwater introduced predators (rats and cats) must be their main threats at breeding colonies. In addition, fledglings are attracted to artificial lights at night during their maiden flights from nests to the sea. On Tenerife, Canary Islands, a decline on the number of birds attracted to lights have been reported, suggesting a population decline on the island. Barolo shearwater The Barolo shearwater ("Puffinus baroli"), also known as the North Atlantic little shearwater or Macaronesian shearwater, is a small shearwater which breeds in the Azores and Canaries of Macaronesia in the North Atlantic Ocean. "Puffinus" is a New Latin loanword based on