Yellow-footed Gull
Larus livens
Large, dark-backed, and stout-billed gull. Adult has dark slaty gray back like Western Gull, but note the rich yellow legs. Immature plumages look much like Western Gull and other large gulls; overall brown in first year with pinkish legs, developing gray back and yellow legs in second year. Restricted range around the Gulf of California in Mexico; some disperse north to the Salton Sea in California. Favors beaches, rocky and muddy intertidal habitats, and fishing harbors.
识别特征
Adults are similar in appearance to the western gull with a white head, dark, slate-colored back and wings, and a thick yellow bill. Its legs are yellow, though first winter birds do display pink legs like those of the western gull. It attains full plumage at three years of age.<p>This species is tied with slaty-backed gull for the world's fourth-largest gull species and is one of the largest gulls in the world, being slightly larger than the western gull. It measures 53 to 72 cm (21 to 28 in) in length and spans 140 to 160 cm (55 to 63 in) across the wings. The body mass of this species can vary from 930 to 1,500 g (2.05 to 3.31 lb). Among standard measurements, the wing chord is 40 to 46 cm (16 to 18 in), the bill is 5.0 to 6.2 cm (2.0 to 2.4 in) and the tarsus is 5.9 to 7.5 cm (2.3 to 3.0 in).
分类信息
- 学名
- Larus livens
- 命名信息
- Dwight, 1919
- 目
- Charadriiformes
- 科
- Laridae
- 属
- Larus
分布与栖息地
Yellow-footed gulls are native to the Gulf of California in Mexico. Most are non-migratory, but an increasing number have been traveling to California's Salton Sea and southwards to Sonora during nonbreeding periods. Their breeding habitat is the Gulf of California, where they nest, in April, either independently or in colonies. They are found on sandy and rocky coasts or islands, often with little vegetation.
- 繁殖区
- NA, MA : islets in Gulf of California, from Roca Consag to La Paz Bay
- 非繁殖区
- to Salton Sea (sc California) and throughout Gulf of California (nw Mexico)
- 迁徙
- Resident species
行为
The birds are scavengers as well as foragers, feeding on small fish and invertebrates, carcases of marine mammals and offal, and preying upon seabird chicks and eggs (including pelican eggs). They sometimes scavenge around waste dumps and docks for refuse but seldom fly far inland.<p>Yellow-footed gulls nest on the beach, a few metres above the upper limits of the highest tides. A pair of birds defends a small territory between the nest and the sea. The nest is a scrape in the sand with a meagre lining of seaweed or dry plant material. Usually, three eggs are laid, olive or buff in color with dark blotches, and incubation is probably done by both parents. The young are fully fledged and leave the nest when they are about seven weeks old.
保护状况
- 种群趋势
- unknown
照片
分布
鸟叫声
其他鸟类
Medium Tree-Finch
Camarhynchus pauper
A critically endangered Galápagos finch found only on the island of Floreana. Bill is moderately curved on both upper and lower edges, and slightly longer than it is deep. Male has a black hood, brownish-olive upperparts, and a pale belly. Female is tan with whitish underparts. Both sexes have faint streaking on the breast. Bill is black on breeding male and orange on female and non-breeding male. Large Tree-Finch has larger and more bulbous bill. Small Tree-Finch has slightly smaller bill and body. Identification is much easier when more than one species is present to allow direct comparison. Medium Tree-Finch inhabits forest mainly in the highlands but is occasionally seen closer to the coast, where it may be only a seasonal visitor.
Fischer's Lovebird
Agapornis fischeri
A colorful lovebird of East African savanna that is also found in woodland, cultivated areas, and towns. Note the green back, the broad yellow collar, the orange face, and the red bill. The flight is fast and direct, on twitching wingbeats. Usually found in flocks that can be quite large. Similar to Yellow-collared Lovebird, but easily separated by the orange rather than black head. However, hybrids showing a mix of the two species’ traits are now common, especially in Kenya and along the coast. The common call is a scratchy “sveet.”
Subtropical Doradito
Pseudocolopteryx acutipennis
A bright flycatcher found in marshes in the Andes from Colombia to Argentina. Yellow below and olive above, sometimes showing a hint of a dark mask and dull yellowish edges on the wing feathers. Distinctive in habitat, although could be confused with a female Masked Yellowthroat, which has a pinkish bill and legs. Forages singly or in pairs; can be difficult to see in dense marsh grasses. Mostly occurs from 1,000 to 3,500 m, but some appear to move into lowlands in the winter in southern part of range. Gives single nasal calls as well as a whirring noise produced by the wings.
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