Large shearwater with dark bill with tube on top and dark brown cap. Grayish-brown upperparts with White uppertail coverts White underparts with indistinct brownish belly Rapid wingbeats. Glides on stiff wings
Oceanic, in cool to fairly cold pelagic waters of South and North Atlantic, migrating quickly without stopping across intervening tropical and sub-tropical seas, and usually avoiding both mid-ocean and inshore zones, preferring (in non-breeding season) chilly climates, even with scattered icebergs, to sunny, warmer currents sought by Cory's Shearwater Calonectris diomedea. Stops short of Arctic pack-ice, and occupies west Palearctic habitats almost exclusively during third quarter of year, sometimes well into October in east Atlantic. Less frequently inshore, or in narrow seas such as English Channel, than Sooty Shearwater Puffinus griseus. In flight, except at breeding stations, confined to lowest belt of airspace, but less aerial than other shearwaters and more given to resting and feeding for long periods on water, often in rafts, making shallow dives below surface. Indifferent to shipping but will approach fishing vessels for food, or follow whales and porpoises. Unaffected by stormy weather. Sometimes overlaps with other shearwaters, but does not normally associate with them. Breeding habitat in South Atlantic up to c. 400 m on any kind of terrain permitting excavation of burrows, including slopes under tussock grass or woodland
Puffinus gravis breeds at three main sites: Nightingale and Inaccessible islands in the Tristan da Cunha group, and Gough Island, Tristan da Cunha (to UK) (Snow and Perrins 1998, Carboneras 1992d). This species has a large range, with an estimated global Extent of Occurrence of 52.8 million km2. A minimum of 5,000,000 pairs are thought to breed at Tristan da Cunha, and 600,000 to 3,000,000 pairs at Gough. Birds also breed in small numbers in the Falkland Islands (to UK), where the only confirmed site is Kidney Island (no more than 15 pairs recorded in 1987), though there is a slight possibilty of breeding near Wineglass Hill, East Falkland, where one has been caught. The species has a large global population estimated to be 16,500,000 individuals. Adults begin a transequatorial migration in April, moving north-west to South America, up to Canada, past Greenland and onto the north-east Atlantic before returning south in November to the breeding islands. The species breeds on sloping ground, mainly in areas of tussock grass or Phylica woodland. It feeds mostly on fish, squid and fish offal (attending trawlers, sometimes in large numbers), and also on some crustaceans.
Follows and catches surface-feeding fishes, also squids, crustaceans, and small fishes such as sand launces; dives under surface for fishes and rises into air to swallow. Also eats offal from fishing boats and apparently whale feces.
Global population trends have not been quantified, but several thousand adults and c.50,000 chicks are harvested every year from Nightingale Island by Tristan Islanders, which could lead to the collapse of the population without research into sustainable harvesting levels. Although there is no real evidence of threats to the tiny confirmed Falkland breeding population, predation by feral cats at Wineglass Hill would be a threat to any breeding there. [conservation status from birdlife.org]
When nesting, parents at sea most of day. Many birds over land at sunset, then come to ground. Night activity peaks at about 9 p.m. and 3:30 a.m. Asleep on ground from about midnight on. Average laying date is 11 Novmnber. Clutch size is 1. Incubation lasts about 55 days. Young are tended by both parents, first fly at about 84 days, depart at about 105 days. Parents depart in April while young still in burrows
Migratory. Absent from main breeding stations chiefly April (adults) and May (juveniles) until late August or early September, when undertakes transequatorial migration into North Atlantic. Present off Newfoundland Grand Banks all through northern summer, and later also off Greenland, adults undergoing rapid moult. Widely distributed western half of North Atlantic in June when northward passage out of tropics still continuing. Virtually all in winter quarters by July, when present north to 65°-66°N in Davis and Denmark Straits; maximum abundance high latitudes early August. During July and August, spreads east across North Atlantic, reaching Rockall Bank and European coasts, mainly well offshore Scotland to Iberian peninsula. Rapid return passage by adults starts August; some back at colonies by end August, and most breeders return by mid-September.