Seabirds in Peril
Of the roughly 10,000 species of birds in the world, fewer than 200 could be classified as true seabirds. Most of these are unfamiliar to the vast majority of people. The mention of seabirds may conjure up images of "seagulls," but most gulls hug the coastline or even live far inland around lakes and rivers; only a few species of gulls occur regularly far out at sea. True seabirds come to land only for the purpose of raising their young, and they spend all the rest of their time on the open ocean. Individuals of many seabird species may go months at a time without seeing land at all.
Seabirds, which are found in all of the world’s oceans, represent several different and unrelated groups. Penguins, limited to the Southern Hemisphere (with one species found as far north as the Equator in the Galapagos), are unable to fly, but are powerful, graceful swimmers. Unrelated but superficially similar are members of the auk family, including puffins, murres, murrelets, and auklets, found mostly in northern seas. All living members of the auk family can fly—the flightless great auk, too vulnerable for modern times, was wiped out before 1850—but they are more skilled as swimmers, diving deep in search of food. Most seabirds, however, are superb fliers, ranging widely over the oceans and often traveling long distances. This is especially true for most members of the order Procellariiformes, which includes the albatrosses, shearwaters, petrels, and storm-petrels. The most numerous seabird off the U.S. Atlantic Coast is often the Wilson’s storm-petrel, while the most numerous off our Pacific Coast is often the sooty shearwater, but neither species nests anywhere north of the Equator: The birds seen in our offshore waters have come from nesting islands below the southern continents.
The challenges of seabird conservation are frequently different from those surrounding conservation of other birds. A key element insaving land birds generally involves protecting blocks of habitat. Seabirds are usually quite concentrated at the places where they nest, which typically are on islands with no natural predators, making them vulnerable to disturbance when humans come to those islands. Out at sea they are often widely dispersed, but they are affected by various kinds of pollution and by the side effects of human fishing operations. Here are some examples of threatened and endangered seabirds and the issues they face.
The Bermuda Petrel and Its Tenuous Hold on Survival
Mariners who visited Bermuda centuries ago referred to this archipelago as "the devil’s islands" because of the unearthly cries that filled the night sky. These were not the voices of demons, as the sailors imagined, but those of seabirds, mainly Bermuda petrels (also called cahow), coming to their nesting burrows under the cover of darkness. Abundant though they had been, these fast-flying seabirds soon disappeared after settlers arrived in Bermuda. Landing on the ground to shuffle into their nesting burrows, the petrels had no defenses against dogs, cats, rats, and the other animals that typically accompany human settlers on islands. The species was believed to be possibly extinct for many years, but a few pairs were found nesting on tiny islets off eastern Bermuda in 1951. One of the people involved in that discovery, a boy named David Wingate, grew up to become the guardian of the species. He found that Bermuda petrels were being evicted from their nesting burrows by aggressive white-tailed tropicbirds, so he made baffles to keep the slightly larger tropicbirds out of the burrows. He also created new artificial burrows for the petrels and carefully monitored the species’ gradual recovery and increase. Despite Dr. Wingate’s best efforts, Bermuda petrels now face a new threat: climate change, which is leading to a gradually rising sea level and to more frequent and violent storms, bringing the possibility that the tiny islands supporting the petrels may be at risk of being flooded out.
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Albatrosses and Longline Fisheries
Albatrosses are large, magnificent fliers, able to glide for hours over the wind-tossed waves with scarcely a flap of their long wings. The larger species are among the birds with the greatest recorded wingspans, such as the wandering albatross, whose wings can measure 11 feet or more from wingtip to wingtip. Albatrosses are most diverse in the southern oceans, with only three species found regularly in the North Pacific and none normally occurring in the North Atlantic. They typically feed on squid and small fish, but they will also follow ships for the scraps thrown overboard, which has led to disastrous levels of mortality caused by longline fishing boats.
Working in deep offshore waters, longliners put out a line up to eighty miles long, with thousands of baited hooks, pulled behind the vessel. As the line is reeled out, if it sinks only gradually, albatrosses and other seabirds may take the bait just below the surface, only to be pulled deeper underwater and drowned. The "bycatch" of seabirds has reached shocking levels in some recent years, with estimates as high as 100,000 albatrosses per year being killed in this way. Albatrosses, which reproduce slowly, do not begin to breed until they are at least five years old, and they raise one young per year at most, so their populations cannot recover quickly from such losses. Of the 21 species of albatrosses, 19 are considered endangered or vulnerable, and longline fishing is the single greatest threat to these birds.
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Marbled Murrelets: Seabirds and Old-Growth Forests
The United States and Canada are home to the only seabird in the world that is dependent for its survival on old-growth forest. The marbled murrelet, a small member of the auk family, was the last North American bird species to have its nesting habits revealed. The first nest was not discovered until 1974, and it was in a shocking location for a seabird: 150 feet above the ground in a giant Douglas fir, six miles from the coast in a dense forest in California. Several more nests have been found since then, and regular observations of marbled murrelets flying into the forest indicate that this bizarre nesting habitat is indeed the norm for the species.
Because of this unique nesting situation, this chunky little seabird joins land birds like the northern spotted owl and mammals like the red tree vole in being dependent on the continued existence of old-growth forests in the Pacific Northwest. However, loss of nesting sites is not the only threat to the marbled murrelet. It usually stays closer to the coast than most seabirds, doing most of its foraging within about three miles of the shore, and this makes it vulnerable to the effects of oil spills. Large numbers of murrelets also may be killed by fishing operations that employ gill nets.
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For more information, please visit the Island Conservation website
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