Greater shearwaters are a marine species distributed throughout the region of the Atlantic ocean. Puffinus gravis breed in the far south Atlantic, mainly on the islands of the Tristan da Cunha group, the Falkland Islands, and Gough Island. P. gravis then migrates to the North Atlantic during the winter, reaching noth-east Canada and sometimes reaching as far north as Greenland. Migration to the breeding grounds involves a flight east, past Britain and Iberia, than turning south to reach their Southern Hemisphere breeding grounds.

(del Hoyo, Elliot, and Sargatal 1992; Farrand 1985; Gooders 1978)

Biogeographic Regions: oceanic islands (Native ); atlantic ocean (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Non-breeding

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Non-breeding

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Breeds in southern Atlantic Ocean on Tristan da Cunha, Gough Island, and in Falkland Islands (Croxall et al. 1984). Ranges at sea throughout Atlantic Ocean from Greenland and Iceland to Tierra del Fuego and South Africa.

Puffinus gravis is a large shearwater species, 43-51cm in length, with a wingspan of 100-118cm. Colouring is unique with a combination of pale underparts with a poorly defined dark patch on the belly. White bands of plumage occur across the uppertail-coverts and also across the hindneck, emphasizing the Greater Shearwaters strongly capped appearance. Upperparts are dark gray-brown to black with light feather edgings to give a scaled appearance. Flight feathers have black upper- and undersurfaces. The tubenosed bill is long, thin, and black. The legs are pink to grey with webbed feet, and eyes are brown. Chicks have bluish-grey down and juveniles are similar to adults but greyer with paler fringes to feathers to give less scaled appearance. There is no sexual dimorphism in terms of size or colour between males and females.

(Campbell 1974; del Hoyo, Elliot, and Sargatal 1992; Farrand 1985; Gooders 1978)

Range mass: 715 to 950 g.

Length: 48 cm

Weight: 849 grams

• Terrestrial
• Marine

P. gravis is a marine, pelagic bird species, frequenting cool offshore and pelagic waters, and breeding on sloping ground, mainly in grassland or woodland areas (del Hoyo, Elliot, and Sargatal 1992; Gooders 1978)

Comments: Pelagic. Nests in burrows on oceanic islands.

The species associated with this page are major players in the pelagic ecosystem of the Stellwagen Bank National Marine Sanctuary. Stellwagen Bank is an undersea gravel and sand deposit stretching between Cape Cod and Cape Ann off the coast of Massachussets. Protected since 1993 as the region’s first National Marine Sanctuary, the bank is known primarily for whale-watching and commercial fishing of cod, lobster, hake, and other species (Eldredge 1993). 

Massachusetts Bay, and Stellwagen Bank in particular, show a marked concentration of biodiversity in comparison to the broader coastal North Atlantic. This diversity is supported from the bottom of the food chain. The pattern of currents and bathymetry in the area support high levels of phytoplankton productivity, which in turn support dense populations of schooling fish such as sand lance, herring, and mackerel, all important prey for larger fish, mammals, and seabirds (NOAA 2010). Sightings of many species of whales and seabirds are best predicted by spatial and temporal distribution of prey species (Jiang et al 2007; NOAA 2010), providing support for the theory that the region’s diversity is productivity-driven.

Stellwagen Bank is utilized as a significant migration stopover point for many species of shorebird. Summer visitors include Wilson’s storm-petrel, shearwaters, Arctic terns, and red phalaropes, while winter visitors include black-legged kittiwakes, great cormorants, Atlantic puffins, and razorbills. Various cormorants and gulls, the common murre, and the common eider all form significant breeding colonies in the sanctuary as well (NOAA 2010). The community of locally-breeding birds in particular is adversely affected by human activity. As land use along the shore changes and fishing activity increases, the prevalence of garbage and detritus favors gulls, especially herring and black-backed gulls. As gull survivorship increases, gulls begin to dominate competition for nesting sites, to the detriment of other species (NOAA 2010). 

In addition to various other cetaceans and pinnipeds, the world’s only remaining population of North Atlantic right whales summers in the Stellwagen Bank sanctuary. Right whales and other baleen whales feed on the abundant copepods and phytoplankton of the region, while toothed whales, pinnipeds, and belugas feed on fish and cephalopods (NOAA 2010). The greatest direct threats to cetaceans in the sanctuary are entanglement with fishing gear and death by vessel strikes (NOAA 2010), but a growing body of evidence suggests that noise pollution harms marine mammals by masking their acoustic communication and damaging their hearing (Clark et al 2009).

General threats to the ecosystem as a whole include overfishing and environmental contaminants. Fishing pressure in the Gulf of Maine area has three negative effects. First and most obviously, it reduces the abundance of fish species, harming both the fish and all organisms dependent on the fish as food sources. Secondly, human preference for large fish disproportionately damages the resilience of fish populations, as large females produce more abundant, higher quality eggs than small females. Third, by preferentially catching large fish, humans have exerted an intense selective pressure on food fish species for smaller body size. This extreme selective pressure has caused a selective sweep, diminishing the variation in gene pools of many commercial fisheries (NOAA 2010). While the waters of the SBNMS are significantly cleaner than Massachusetts Bay as a whole, elevated levels of PCBs have been measured in cetaceans and seabird eggs (NOAA 2010). Additionally, iron and copper leaching from the contaminated sediments of Boston Harbor occasionally reach the preserve (Li et al 2010). 

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Migrates north in western Atlantic in northern spring and summer (mainly May-September off U.S. coast).

Greater Shearwaters feed in groups where aggressive intraspecific feeding competition is evident through lashing with bills and wings. They eat mostly fish and squid, with occasional feeding on crustaceans, fish entrails, and other refuse discarded by fishing vessels. They hunt by plunge-diving from heights of 6-10m or taking prey from surface seizing or pursuit diving.

Surface-seizing consists of the 'walking on water' that is usually associated with Storm Petrels. Without entirely folding its wings, a Greater Shearwater lands on the water surface with its feet, balances with its wings, and "walks" forward over the water as it picks up food from near the surface.

Plunge-diving involves striking the water surface from heights of 6-10 m with belly and feet and then instantly lowering the head under the water surface to lead into a smooth submersion. Occasionally, a Greater Shearwater might briefly halt 0.5 m above the water surface, spread its feet, then plunge headfirst underneath the water. After the dive, the bird bursts out of the water and almost directly into flight.

(Brown, Bourne, and Wahle 1978; del Hoyo, Elliot, and Sargatal 1992; Gooders 1978)

Comments: 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.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 1 - 20

Comments: Breeds at only four sites.

>1,000,000 individuals

Comments: More than 5 million pairs nest on Tristan da Cunha, and between 600,000 and 3 million pairs nest on Gough Island (del Hoyo et al. 1992).

Comments: 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. See Palmer (1962).

Average lifespan

Status: wild: 85 months.

The breeding season commences in October and often lasts until December. Breeding takes place in the Southern Hemisphere and is restricted to the far south oceanic islands: Tristan da Cunha group, Falkland Island, and Gough Island. Puffinus gravis is a colonial nester, nesting in burrows or crevices among boulders along hilly island shores. The female produces a single, white, oval, and slightly pointed egg. The egg is incubated for 53-57 days, and an altricial offspring is then hatched. Both male and female care for young. Offspring become independent of their parents at about 105 days. (del Hoyo, Elliot, and Sargatal 1992; Gooders 1978)

Average laying date is 11 Novenber. 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. Average of 1.6 nesting burrows/sq yd (Palmer 1962).

Greater Shearwaters are not globally threatened. They are abundant with enormous total populations of a minimum 5 million breeding pairs on Tristan da Cunha, 600,000 to 3 million pairs on Gough Island, and small numbers on Falkland Islands. Their breeding range is restricted with only 4 sites known. Where the problem lies is with exploitation by Tristan islanders. Each year, a few thousand adults, and 50,000 chicks are taken. This could lead to a population collapse unless a quota system is established to allow for rational exploitation. More research is required in this area, as well as in the areas of the impact of harvesting on Greater Shearwaters, and the importance of other causes of mortality and population dynamics, in order to determine the maximum sustainable levels of exploitation. Another issue to be addressed is that of the occasional Greater Shearwater that is snared by fishermen's baited hooks.

Very little research has been done, but is required to ensure the maintenance of healthy populations of Puffinus gravis worldwide.

(del Hoyo, Elliot, and Sargatal 1992)

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5N - Secure

United States

Rounded National Status Rank: N5N - Secure

Rounded Global Status Rank: G5 - Secure

Comments: Vulnerable because of restricted breeding distribution. A few thousand adults and about 50,000 chicks are harvested each year on Tristan da Cunha (del Hoyo et al. 1992).

In the past, Greater Shearwaters had been used to provide food and bait for seamen, but this practice has long since been discarded and aside from the occasional contact with fishermen, and Tristan islanders, P. gravis has mostly no contact with humans.

 (del Hoyo, Elliot, and Sargatal 1992; Cassidy 1990)