16,500,000
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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.
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.
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.
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.
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.
