Their diet consists mainly of squid. Mortality is is very high in the first year, but those which survive can reach ages well over 50. Weighing over 20 lbs. Plumage varies through its life, from dark brown in the first year to almost fully white in old age. Its upperparts are dark grey, blending to blackish-grey towards the back with a white rump.
Underparts are white.
Sooty brown color with grey buff mantle and lower back with a prominently dark head. They are characteristically marked by deeply grooved and hooked bills. They have long nostrils, indicating a strong sense of smell, unusual for birds. The giant petrels are the largest of the petrel family. Unlike albatrosses, giant petrels forest on both land and sea.