Greater Shearwater

Puffinus gravis

Image by Arthur H. Kopelman, PhD, Coastal Research & Education Society of Long Island
  • PROCELLARIIDAE
  • Shearwaters, Fulmars, Petrels
  • Procellariiformes
  • Pampero Mayor
  • Puffin majeur
Introduction

On the coastal waters of the northeastern seaboard, the Greater Shearwater is sometimes common in summer, but it rarely ventures close enough to shore to be seen from land. Boats often attract this large seabird, and North American fishermen have given it many names, like the hagdon or hag. John James Audubon was impressed with its graceful, easy flight and its method of self defense: stinky oil ejected from its nostrils.

Appearance Description
Resembling a small albatross, the Greater Shearwater is a large seabird growing to 18 inches long with a 3½-foot wingspan and weighing 1.8 pounds. The sexes appear alike. The long, narrow wings are usually held unbent in flight. The brown upperparts are darker at the wing tip and the tail. The best field mark is a white band that separates the tail from the brown rump. A dark brown cap covers the eye and contrasts with the bright white face, neck, and chest. The center of the underwing is white, outlined in dark brown. The brown belly, undertail, and collar distinguish the Greater Shearwater from other seabirds in the Western Atlantic. The eyes and bill are black.
Range Map
Courtesy Kenn Kaufman
Range Distribution
During our winter, the Greater Shearwater breeds on remote islands in the far southern Atlantic Ocean, including the Tristan da Cunha group and the Falkland Islands. From June through September, its "wintering" range stretches over cooler Atlantic waters, near shore from north Florida to Newfoundland. In the northern summer, most Greater Shearwaters scatter over this range but sometimes concentrate at feeding hot spots, like Stellwagen Bank off the tip of Cape Cod, Massachusetts. In fall, staging flocks have been estimated over 200,000 off New England's coast.
Habitat
In the northern summer, the Greater Shearwater frequents the cool to cold waters of the continental shelf, occasionally near the shore. Shearwaters gather where ocean upwellings and strong surface currents concentrate food. In the far southern Atlantic Ocean, the convergence zone between subtropical and Antarctic waters is used for foraging in summer. Breeding occurs on remote, volcanic islands with loose and peaty soils soft enough for digging nest burrows.
Feeding
The Greater Shearwater's feeding habits probably depend most on its sense of smell. One of the "tubenose" seabirds, its nostrils are set in a little pipe at the base of the bill. Skimming the ocean's surface, the Greater Shearwater detects the smell of food and then hones in by sight. Squid and small fish like the sand lance are plucked from the water in flight or are captured in shallow dives. Concentrated food sources can result in a frenzy of shearwaters. Foraging may be mostly at night, when deeper water squid rise to the surface. This shearwater will follow fishing boats for scraps and bycatch. Birdwatchers can draw it in by casting fish byproducts (chum) onto the water.
Reproduction
As early as September, large flocks of Greater Shearwaters stage offshore for several days before moving onto rocky islands to breed. Densely packed colonies number in the millions of pairs, and most shearwaters reuse old nest sites. Sitting close together on the ground, the pair cements its bonds by softly biting each other's neck and rump in turns, as the stimulated bird coos. This ritual is interspersed with bouts of raucous calls. Dug in loose or soft soil, the burrow is about three feet long, with a sharp turn placed near the surface. In early November, one white egg is laid deep in the nest chamber, which is sometimes lined with grass. Both parents share incubation of the egg for approximately 55 days. Foraging by day, adults gather offshore before approaching their burrows well after dark. The chick is attended by both parents and fledges in about 84 days, usually after the parents have abandoned it.
Migration
The Greater Shearwater migrates long distances along the entire length of the Atlantic Ocean. Warmer waters are crossed quickly. In late April, migrants begin moving north through the Western Atlantic to arrive off the eastern coast of the United States in June. As the northern summer progresses, some of these "wintering" shearwaters drift eastward and become common off the Spanish coast. Fall migration sometimes concentrates enormous flocks on the edges of the European and North American continental shelves in late October and early November.
  • 16,500,000
Population Status Trends
Breeding populations of the Greater Shearwater are large, with 4½ million pairs estimated on the Tristan da Cunha Islands in the year 2000. These islands contain most of the world population, which makes the species vulnerable despite its large numbers. Between 1990 and 2002, the Waterbird Conservation Plan estimated a declining population of Greater Shearwaters in North American waters, but numbers for such estimates are very soft. Shearwaters are difficult to count, because breeders approach burrows at night, and non-breeders may wander the entire Atlantic Ocean. Population trends have not been calculated.
Conservation Issues
At sea, the accumulation of small oil spills and deadly conflicts with fisheries present threats, while on land predators introduced on breeding islands jeopardize the abundance of this great seabird. The American Bird Conservancy Green List and the North American Waterbird Conservation Plan (2002) consider the Greater Shearwater a species of High Concern due to apparent population declines in North American waters. New York and New Jersey also share this listing. The causes for these declines are not clear. Chronic oil leaks, which account for the deaths of 300,000 seabirds each year in Canadian waters, may play a part.

Longline fisheries may be another factor, since the Greater Shearwater closely follows boats and frequents popular fishing grounds. Concealment devices may deter shearwaters from baited hooks. Recent regulations from the National Oceanic & Atmospheric Administration (NOAA) have begun to restrict the season and geographical area for longlining. In August 2004, NOAA banned "J" hooks, which can accidentally catch green sea turtles, as well as seabirds. The effects of over-harvesting of fisheries, which may limit food sources for shearwaters, have not been studied.

The greatest potential threat to the Greater Shearwater is on the Tristan da Cunha Islands, where it breeds. Once uninhabited, these islands were free of ground predators, until European colonists brought cats, dogs, mice, and rats. These invasive species destroyed the large breeding colony on Tristan's main island. In 1975, the British and local governments began protecting the Gough and Inaccessible Islands. In 1995, Gough was listed as a World Heritage Site, and Inaccessible Island was added in 2004. Despite the absence of wharves and strict regulations for visitors, introduced mice are a severe problem on Gough, with its colony of 1.2 million Greater Shearwaters. In 2006, an estimated 700,000 house mice (Mus musculus) were infesting the island and killed an estimated 1 million seabird chicks of several species. In order to protect seabird colonies, carnivorous rodents have been exterminated from other islands, like Lundy Island in the British Channel (2006) and Langara Island, British Columbia (1996). Plans to manage or eradicate the house mouse on Gough Island should be supported.
What You Can Do
Look for the Greater Shearwater from mid to late summer off the Atlantic Coast. Shearwaters often associate with surface feeding whales, like the Humpback Whale, and can be seen from whale watching boats from New York to Nova Scotia.

Know how your seafood is caught or produced. Some harvesting and farming practices are less stressful to the Greater Shearwater's environment than others. You can start with Audubon's overviews of longline fisheries and sea food guide . Or check out the Monterey Aquarium's web site for additional information.

Participate in a beach clean-up. Plastics in the form of ties, plastic bags, and fishing line can entangle or choke seabirds like the Greater Shearwater.

Advocate for the clean disposal of waste oil, from large cargo ships and even from the local garage. Ocean currents, rivers, and storm runoff can transport oil to coastal environments.
More Information
The United Nations Environment Programme has a detailed fact sheet for the Gough and Inaccessible Islands World Heritage Site, that explains its history, conservation status, and ecology.
Natural History References
"Great Shearwater Puffinus gravis." Handbook of the Birds of North America: Volume 1. Edited by Ralph S. Palmer. New Haven, Connecticut: Yale University Press, 1976.

"Greater Shearwater Puffinus gravis." Proceedings of the Second International Fishers Forum. Edited by Noreen M. Parks. (Honolulu, Hawaii: November 19-22, 2002) 199-200. Accessed 25 May 2007.

Kaufman, Kenn. Lives of North American Birds. Houghton Mifflin Company, New York, 1996.

Sibley, David Allen. 2000. The Sibley Guide to Birds. Alfred A. Knopf, New York.
Conservation Status References
Audubon, John James. F. R. SS. L. & E. "The Wandering Shearwater." Birds of America (First Octavo Edition, 1840). National Audubon Society, Inc. 2005. Accessed 25 May 2007.

"Greater Shearwater Puffinus gravis." Proceedings of the Second International Fishers Forum. Edited by Noreen M. Parks. (Honolulu, Hawaii: November 19-22, 2002) 199-200. Accessed 25 May 2007.

Kushlan, James A. et al. North American Waterbird Conservation Plan, Version 1. Waterbird Conservation for the Americas, Washington, D.C., 78 pages.

MANEM Waterbird Working Group. 2006. Waterbird Conservation Plan Mid-Atlantic/New England/Maritimes Region: 2006-2010. Review Draft. Waterbird Conservation for the Americas. Accessed 16 May 2007.

"Metre-high seabird chicks being eaten alive by mice - Millions killed on UK bird colony." Media Release, Royal Society for the Protection of Birds, 25 July 2005. Tristan da Cunha Government and the Tristan da Cunha Association (2007). Accessed 26 May 2007 from Tristan da Cunha Conservation News.

Sibley, David Allen. 2000. The Sibley Guide to Birds. Alfred A. Knopf, New York.