Glaucous-winged Gull
Larus glaucescens
Large, stocky gull of the North Pacific. Generally fairly pale and uniform-looking; at all ages, note wingtips and back are approximately the same color. Takes four years for immatures to progress from mostly brown to fully white and gray adult plumage; intermediate plumages are often mottled and messy. Most immatures look frosty grayish-brown with smooth patterning. Found in coastal areas, including beaches, mudflats, and even city parks. Identification is complicated by frequent hybridization with Western, Herring, and Glaucous Gulls in various parts of range. Pure birds can be difficult to find and identify with certainty, and many intermediate birds are best left unidentified.
识别特征
This gull is a large bird, being close in size and shape to the closely related Western gull (L. occidentalis). It measures 50–68 cm (20–27 in) in length and 120–150 cm (47–59 in) in wingspan, with a body mass of 730–1,690 g (1.61–3.73 lb). It weighs around 1,010 g (2.23 lb) on average. Among standard measurements, the wing chord is 39.2 to 48 cm (15.4 to 18.9 in), the bill is 4.6 to 6.4 cm (1.8 to 2.5 in) and the tarsus is 5.8 to 7.8 cm (2.3 to 3.1 in). It has a white head, neck, breast, and belly, a white tail. The silver-gray wings and back form the mantle, which is darker than that of the Glaucous gull and paler than the Herring gull and Western Gull. The primary flight feathers (wingtips) are grey, usually the same shade as the mantle. Its legs are pink and the beak is yellow with a red subterminal spot (the spot near the end of the bill that chicks peck in order to stimulate regurgitative feeding). The irises are typically dark, and surrounded by pink orbital skin. The forehead is somewhat flat. During the winter, the head and nape is darker with a varied smudged or mottled pattern, and the bill colour becomes duller, often with dark markings near the tip. Young birds are brown or gray with black beaks, and take four years to reach adult plumage.
分类信息
- 学名
- Larus glaucescens
- 命名信息
- Naumann, JF, 1840
- 目
- Charadriiformes
- 科
- Laridae
- 属
- Larus
分布与栖息地
- 繁殖区
- PAL, NA : coastal North Pacific in e Siberia, Kamchatka, Kuril and Commander is. (e Russia); Aleutian and Pribilof is., sw Alaska mainland to n Washington
- 非繁殖区
- to Japan and California
- 迁徙
- Complete migrants
行为
The glaucous-winged gull nests in the summer, and each pair produces two or three chicks which fledge at six weeks.<p>It feeds along the coast, scavenging for dead or weak animals, fish, mussels and scraps. In urban areas it is well known for its tendency to accept food from people and peck open unprotected garbage bags in search of edibles.<p>Its call is a low-pitched "kak-kak-kak" or "wow", or a more high-pitched wailing.
保护状况
- 种群趋势
- rising
照片
分布
鸟叫声
其他鸟类
Frilled Coquette
Lophornis magnificus
Tiny hummingbird that is gray and green above and gray below. Like other coquettes it has a white bar across the rump. Males are astonishingly pretty with an orange crest, a ruff of white and green feathers on the neck, and a red bill with a black tip. Females have a white belly, and spotted throat, lacking the male’s crest and orange bill. Found at forest edges, in second growth habitats and in wooded savanna.
Sargasso Shearwater
Puffinus lherminieri
Small black-and-white shearwater with relatively long tail and somewhat rounded wings. Usually flies low to the water with fluttering wingbeats, but in strong winds it can fly with high wheeling arcs. Undertail coverts are typically dark, but this can be very difficult to see in the field. Compare with Manx Shearwater, which is larger with longer, more pointed wings, light undertail coverts, and a darker face. Found over warm tropical waters, especially around floating mats of Sargassum weed. Often seen singly or in pairs but can gather in loose flocks, sometimes loafing with other shearwater species.
Lesser Elaenia
Elaenia chiriquensis
Confusing flycatcher, fairly small and nondescript. Like many other elaenias and flycatchers, brownish-olive above, pale gray on the throat, and pale yellow on the belly, with whitish wingbars. Only shows a slight crest and very little facial pattern. Usually seen in more open habitats like forest edge or second growth, singly or in pairs, sometimes following a mixed-species flock. Best identified by voice, which varies across range. Call is typically a single high-pitched “pseew”, sometimes buzzy and sometimes clear. Also gives a harsh stuttered song, varying from a short “chi-bur” to a longer series of notes.
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