The Northern Giant Petrel is a large seabird whose plumage becomes paler with age. It breeds on subantarctic islands and feeds at sea on fish and squid.
It is dark grey, with a whitish face and chin and white mottling on the head, neck, and breast. Juveniles have dark eyes, while adults have pale grey eyes.
At Bird Island in South Georgia, researchers followed breeding pairs of Northern and Southern Giant Petrels over many years. Mixed-species pairs accounted for 0.4 to 2.4 percent of pairs each year, with a mean of 1.5 percent. The study found no linear increase or decrease in their proportion over the observation period.
Breeding success for mixed pairs was 15.6 percent, lower than for pairs of the same species. The histories of individual birds varied: some later bred with a same-species partner, while some mixed pairs stayed together across multiple seasons. Researchers also documented the first verified back-cross between a hybrid giant petrel and a female Northern Giant Petrel.
An extinction-risk assessment has not been added yet.
At Bird Island, mixed Northern and Southern Giant Petrel pairs made up 0.4–2.4% of pairs each year, averaging 1.5%; their breeding success was 15.6%.