Synopsis
Book by American Bird Conservancy
Extrait
Chapter 1
1. Aleutian/Bering Sea Islands
Included in this region are the Aleutian Islands, extending westward from the Alaskan mainland for 1,100 miles, and the Bering Sea Islands, including the Pribilofs, St. Matthew, Hall, St. Lawrence, and Little Diomede. The Aleutian chain is volcanic in origin with a maritime climate in which wind is ever present. Vegetation at higher elevations consists of dwarf shrub communities, mainly of willow and crowberry. Meadows and marshes of herbs, sedges, and grasses are plentiful, and some islands have ericaceous bogs. Sea ice does not extend to the Aleutians, and permafrost is generally absent; however, sea ice is an important feature of the Bering Sea. Seabirds are a dominant component of this region's avifauna and several species, the Red-legged Kittiwake, the Least Auklet, and the Whiskered Auklet, breed only in this region. Southern Hemisphere procellariiforms occur regularly in the offshore waters of the southern Bering Sea and northern Gulf of Alaska during Alaskan summers. The breeding diversity of passerines (mainly the Lapland Longspur, Snow Bunting, and Gray-crowned Rosy-Finch), and shorebirds (including the Black Oystercatcher, Dunlin, Ruddy Turnstone, and Rock Sandpiper) is low. However, the McKay's Bunting, the only endemic Alaskan passerine, is restricted to this area.
Bering Sea Islands IBAs, Alaska
St. Lawrence Island (1), St. Matthew and Hall Islands (2), Pribilof Islands (3)
© Highlight: Remote windswept islands designated for the breeding McKay's Bunting (St. Matthew and Hall, possibly also St. Lawrence and Pribilofs), and for the Red-legged Kittiwake (75 percent of world population breeds in the Pribilof Islands).
© Designation: The Alaska Maritime National Wildlife Refuge, which administers much of the islands, is a National Natural Landmark.
© Location: Includes St. Matthew and Hall Islands (60ƒ N, 172ƒ W), the Pribilof Islands (57ƒ N, 170ƒ W), and St. Lawrence Island (63ƒ N, 170ƒ W).
© Size: Bering Sea Unit of the Alaska Martime Wildlife refuge is 170,000 acres. The Bering Sea Wilderness Area is 81,340 acres.
© Ownership: Private and federal: Alaska Maritime National Wildlife Refuge, Bering Sea Wilderness Area.
© Habitats: Windswept tundra, precipitous cliffs, some lower-lying coastal lagoons, and beaches.
© Land Use: Wilderness. Some subsistence hunting and offshore commercial fishing.
© Site Description: Two groups of remote, windswept islands separated by 200 miles of ocean, and one larger (100-mile-long) island that lies around 150 miles farther to the north. The islands are treeless and covered in low spongy tundra with grasses reaching a foot high in places. Some dwarf willows are also present. The northerly St. Lawrence and St. Matthew and Hall Islands (81,340 acres, of which 77,000 is St. Matthew) are surrounded by pack ice nine months of the year. The bleak climate is characterized by high winds and frequent fog. St. Matthew rises to 1,500 feet in altitude, and the steep sea cliffs of nearby Pinnacle Island reach 1,200 feet. The tiny, northerly Hall Island has a hauling-out site for Pacific walrus. St. Matthew has a lake with endemic landlocked chinook salmon, and singing voles and Arctic foxes are the common terrestrial mammals. Of the five islets that make up the more southerly Pribilof Islands, St. Paul is the most frequently visited by birders, although 90 percent of the breeding seabirds occur on nearby St. George. The low tundra of the islands is punctuated by rocky outcrops, and the volcanic soil is a reddish color. During the summer the landscape is brightened by a flush of colorful wildflowers, and there are two lakes on St. Paul where waterfowl and shorebirds gather. There is a colony of approximately one million northern fur seals, of which the majority are found on St. Paul, a herd of wild reindeer, and naturally occurring Arctic foxes. The Pribilofs are also home to a large Aleut-Russian community, many of whom are Russian Orthodox.
© Birds: The islands are best known for their seabird colonies with two million birds, principally Least Auklets, murres, and fulmars, in the northerly group, and three million in the Pribilofs where a similar mix of species occurs, with the notable addition of 75 percent of the world's Red-legged Kittiwakes. Other seabirds include the Black-legged Kittiwake, Crested and Parakeet Auklets, and Horned and Tufted Puffins. The majority of the Red-legged Kittiwake breed on St. George Island, but the population has declined 50 percent from around 220,000 birds in the mid-1970s. The reason for this decline is not known but appears to be linked to food shortages at sea. The Red-legged Kittiwake has a larger eye than the Black-legged, and this may be an adaptation for specialized night feeding (although both species are known to feed at night). The Pribilofs are also known to birders as a location for Asian vagrants, although the islands are of little, if any, conservation significance for these species. McKay's Bunting has a tiny isolated breeding population on St. Matthew and Hall Islands, where it nests in rocky areas and along shingle beaches (probably also occasionally breeding on St. Lawrence Island). It is also found in the Pribilofs and may have bred there, and migrates to the western Alaska coast in October, returning to breed in May. The population is probably between 3,000 and 6,000 individuals. Other species of interest include the Red-faced Cormorant, Rock Sandpiper, and Gray-crowned Rosy-Finch. St. Lawrence has more than 3.5 million breeding seabirds, including large numbers of Least Auklets (1.3 million at Singikpo Cape alone), as well as Crested Auklets, and Thick-billed and Common Murres. There are also large numbers of nesting Dunlin, and the Pribilofs have an endemic breeding race of the Rock Sandpiper. Recently discovered winter single-species concentrations of Spectacled Eiders in ice-free areas of the Bering Sea may include upward of 300,000 individuals.
© Conservation Issues: Seabird nesting success has been variable in recent years, probably in response to natural fluctuations in food availability, but the possibility that the decline of the Red-legged Kittiwake may be linked to overfishing requires research. In 1982, kittiwake nesting cliffs on St. George were purchased by the government and included in the Alaska Maritime National Wildlife Refuge. Introduced Norway rats or mustelids could wreak havoc on seabirds and on the McKay's Bunting, and must not be allowed to establish a foothold. The McKay's Bunting must be considered vulnerable due to its tiny population and limited range. Any major environmental disaster (especially predator introduction) affecting St. Matthew Island could threaten the species' existence. The Fish and Wildlife Service has already developed a rat response plan for the islands, but the development of rat-proof nest boxes may be a useful precaution.
© Visitor Information: St. Paul is the most common destination for birders and along with the seabirds, and occasional McKay's Buntings there, Asian vagrants are a major attraction. Visit during the summer as seabirds are present only between May and August. Tours to the Pribilofs can be arranged by contacting Peninsula Airways at 800-448-4226 and the Tanadgusix Native Corporation at 907-278-2312 (three- to eight-day tours of St. Paul). The King Eider Hotel can be reached at 907-546-2477. The hotel on St. George can be reached at 907-859-9222.
Aleutian Islands/Alaska Maritime National Wildlife Refuge (4), Alaska
© Highlight: World alcid capital. Includes most of the world breeding population of the rare, endemic Whiskered Auklet and several huge "bird cities" with more than 200,000 breeding seabirds of more than a dozen species. Breeding Red-legged Kittiwakes on one island; significant wintering population of Emperor Geese. Some Steller's Eiders winter in the east. Bristle-thighed Curlews during migration. Classic birding for Asian vagrants on eastern islands.
© Designation: Alaska Maritime National Wildlife Refuge is a National Natural Landmark.
© Location: A chain of more than 2,400 islands stretching 1,000 miles from 163ƒ W to 172ƒ E, and lying between 52ƒ and 54ƒ N. Of the more than 2,400 islands, the following are the most significant for breeding seabirds: Buldir, Chagulak, Kaligagan, Kiska, Segula, and Gareloi.
© Size: Two million acres: Aleutian Islands Unit of the Alaska Maritime National Wildlife Refuge.
© Ownership: Mostly federal: Alaska Maritime National Wildlife Refuge is owned by the Fish and Wildlife Service. Adak is a Navy base, and Shemya is an Air Force base. Attu has a small Coast Guard base. Some land is privately owned by native corporations.
© Habitats: Low-lying, naturally treeless maritime tundra, snow-covered volcanoes, steep sea cliffs up to 200 feet.
© Land Use: Mostly wilderness. Some subsistence hunting. Commercial fisheries based out of Dutch Harbor, Unalaska. Some military installations.
© Site Description: The Aleutian Islands extend from the tip of the Alaska Peninsula in the east to remote Attu Island in the west. They comprise around twenty large islands, and more than 2,400 smaller islands, lying at the junction of the northern Pacific Ocean and the Bering Sea, where two crustal plates collide, generating substantial seismic and volcanic activity. The islands are formed from the peaks of an arc of submerged mountains, including 57 volcanoes (13 above 5,000 feet) more than 40 of which have been active during the last 250 years. The archipelago is surrounded by some of the most productive seas in the world, and birds provide a vital link in the ecological chain by contributing large amounts of nitrogen and phosphate through their droppings. The islands include the most southerly land area in Alaska, and are characterized by treeless maritime tundra, snow-c...
Les informations fournies dans la section « A propos du livre » peuvent faire référence à une autre édition de ce titre.
