Glaucous Gull
Larus hyperboreus
Very large, pale gull. Adults are mostly white with a very pale gray back; note pure white wingtips. Immatures are white or pale tan with light brown markings; also look for the distinctive pink bill with sharply demarcated black tip. Most similar to Iceland Gull but larger, larger-billed, and usually even paler; Iceland typically shows more dark markings on wingtips. Also note shorter wingtips on Glaucous that do not extend far past tip of tail. Breeds in the High Arctic; winters farther south in a variety of habitats, rarely far from a large body of water. Often seen in small numbers mixed with flocks of other large gulls. Hybridizes with Glaucous-winged Gull and Herring Gull in parts of range; hybrids can show any mix of intermediate traits and are sometimes best left unidentified.
识别特征
This is a large and powerful gull, second-largest of all gull species and very pale in all plumage, with no black on either the wings or the tail. Adults are pale grey above, with a thick, yellow bill. Juveniles are very pale grey with a pink and black bill. This species is considerably larger, bulkier, and thicker-billed than the similar Iceland gull, and can sometimes equal the size of the great black-backed gull, the oft-titled largest gull species. In some areas, glaucous gulls are about the same weight as great black-backed gulls or even heavier, and their maximum weight is greater. They can weigh from 960 to 2,700 g (2.12 to 5.95 lb), with the sexes previously reported to average 1.55 kg (3.4 lb) in males and 1.35 kg (3.0 lb) in females. At the colony on Coats Island in Canada, the gulls are nearly 15% heavier than some other known populations, with a mean weight 1.86 kg (4.1 lb) in five males and 1.49 kg (3.3 lb) in seven females. One other study claimed even higher weights for glaucous gulls, as on Wrangel Island, 9 males reportedly averaged 2.32 kg (5.1 lb) and 2.1 kg (4.6 lb) in six females, which if accurate, would make the glaucous gull the heaviest gull and shorebird in the world if not (as far as is known) the largest in length on average. These gulls range from 55 to 77 cm (22 to 30 in) in length and can span 132 to 170 cm (52 to 67 in), with some specimens possibly attaining 182 cm (72 in), across the wings. Among standard measurements, the wing chord is 40.8 to 50.1 cm (16.1 to 19.7 in), the bill is 4.9 to 6.9 cm (1.9 to 2.7 in) and the tarsus is 6 to 7.7 cm (2.4 to 3.0 in). They take four years to reach maturity.<p>The call is a "laughing" cry similar to that of the herring gull, but deeper.
分类信息
- 学名
- Larus hyperboreus
- 命名信息
- Gunnerus, 1767
- 目
- Charadriiformes
- 科
- Laridae
- 属
- Larus
分布与栖息地
This gull breeds in Arctic regions of the Northern Hemisphere and winters south to shores of the Holarctic.It is migratory, wintering from in the North Atlantic and North Pacific Oceans as far south as the British Isles and northernmost states of the United States, also on the Great Lakes. A few birds sometimes reach the southern USA and northern Mexico.
- 繁殖区
- PAL, NA : circumpolar Arctic coasts
- 非繁殖区
- coasts of Hudson Bay to ne Canada, Greenland, Iceland, nw Europe (n North Atlantic); Sea of Okhotsk, Japan, sw Alaska and sw Canada; widely vagrant farther s and inland
- 迁徙
- Complete migrants
行为
This species of seagull breeds colonially or singly on coasts and cliffs, making a lined nest on the ground or cliff. Normally, two to four light brown eggs with dark brown splotches are laid.<p>These are omnivores like most Larus gulls, and they eat fish, insects, molluscs, starfish, offal, scraps, eggs, small birds, small mammals, and carrion, as well as seeds, berries, and grains.
保护状况
- 种群趋势
- stable
照片
分布
鸟叫声
其他鸟类
Green Racquet-tail
Prioniturus luconensis
A rare medium-sized parrot of lowland and foothill forest on Luzon. The two central tail feathers have extended shafts ending in a racket shape. Overall green in color, slightly darker on the back, with paler head and underparts and a pale bill. Male is more yellowish-green in color. Overlaps geographically with Luzon Racquet-tail, but Green is found at lower elevations and lacks the brownish back. Also overlaps with Blue-naped Parrot, but has a pale rather than red bill. Voice consists of ringing metallic squawks.
Rufous-tailed Weaver
Histurgops ruficauda
A large, unusual and distinctive weaver with scaly plumage, rufous tail and wing panels, a white-edged shoulder, and pale eyes. Found in moderately moist savanna and woodland at middle elevations, often in small flocks. Nests in colonies. Similar in shape and size to Red-billed Buffalo-Weaver, but separated by many details, such as the lack of a red bill. The vocalizations are harsh nasal “skeeya” and “krrrra” notes, sometimes strung together into a series.
Buff-shouldered Widowbird
Euplectes psammacromius
Breeding males are mostly black with a long tail. There is a large yellow-and-buff patch on the shoulder. Females and non-breeding males are streaky and brown, though males retain their colorful shoulder. Found locally in montane marsh, heath, and grassland. Vocalizations include low rasps and twittering and sizzling calls. Male separated from Marsh Widowbird by its more extensive buff shoulder patch. Female can be confused with several other species, but is usually identified by association with buff-shouldered males.
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