The northern giant petrel breeding season generally begins towards the end of the Austral winter, with pairs establishing a nest site in August and laying a single egg between August and October (7) (8). The small, loose breeding colonies generally comprise less than 50 pairs, with the untidy nests dispersed widely amongst tussock grass and rocky out-crops (3). The eggs are incubated for around 60 days, and the chicks fledge around 108 days after hatching (2) (3). Reproductive maturity is reached at around six years of age, but most individuals first breed three to five years later (3) (7) (8).
Northern giant petrels are the scavengers in the Southern Ocean. The large beak is particularly well designed for tearing flesh. They feed opportunistically on a wide variety of prey including seal, whale, and penguin carrion, krill, octopus, squid, fish and other seabirds (3) (6) (9). Females forage mostly over the ocean, but males scavenge more on land for seal and penguin carcasses (3) (9) (10). At sea, both male and females are aggressive and often gregarious when feeding, taking most prey by seizing it at the surface, or briefly diving into the water (3) (6). In addition, this species commonly scavenges for fish and offal discarded from ships, often feeding near trawlers and longliners (5) (6) (9).
At some localities where both northern and southern giant petrels breed, some interbreeding between the sibling species occurs. However, the occurrence of hybrid northern and southern giant petrel chicks is rather low because of the difference in the timing of breeding of both species. Northern giant petrels breed six weeks earlier on locations where also southern giant petrels breed (7).