White Tern
Gygis alba
A medium-sized tern with entirely white plumage, a slightly forked tail, and glittering inky pools for eyes. The bill is black with a blue base. Graceful and buoyant in flight. Breeds in trees and both natural and artificial ledges on coral islands. Sometimes flies very high in pairs or trios. Often seen offshore from boats, though most frequently encountered foraging over inshore waters.
识别特征
The white tern has a wingspan of 76–87 cm (30–34 in). It has white plumage and a long black bill. Nesting on coral islands, usually on trees with small branches but also on rocky ledges and on man-made structures, the white tern feeds on small fish which it catches by plunge diving. Giant tortoises have been observed to hunt the bird on Fregate Island in the Seychelles.
分类信息
The white tern was first formally described by the Swedish naturalist Anders Sparrman in 1786 under the binomial name Sterna alba. The genus Gygis was introduced by the German zoologist Johann Georg Wagler in 1832. The name Gygis is from the Ancient Greek guges for a mythical bird and the specific alba is Latin for "white".<p>Molecular phylogenetic studies have shown that the white tern is more closely related to the noddies than it is to the other terns. This implies that "white noddy" would be a more appropriate English name.<p>The white tern has the following recognized subspecies:<p>Some authors have postulated that there may be three species of Gygis: Gygis alba, in the Atlantic Ocean, and Gygis candida and Gygis microrhyncha, both in the Pacific.
- 学名
- Gygis alba
- 命名信息
- (Sparrman, 1786)
- 目
- Charadriiformes
- 科
- Laridae
- 属
- Gygis
分布与栖息地
The white tern ranges widely across the Pacific Ocean from the coasts of Chile and Colombia to New Zealand and along the eastern and southern coasts of Asia from China to India, South Maldives, the islands of the Indian Ocean, and the coast of South Africa. Rarely it is also found in Japan, Madagascar, Mexico, and on some islands in the Atlantic Ocean. It is a pelagic and epipelagic bird, living along the coast and moving into wooded areas during the breeding season.
- 繁殖区
- TrO : widespread on tropical and subtropical is. (except Caribbean, n, e Indian Ocean)
- 非繁殖区
- tropical seas
- 迁徙
- Resident species
行为
This species is notable for laying its egg on bare thin branches in a small fork or depression without a nest. This behaviour is unusual for terns, which generally nest on the ground, and even the related tree-nesting black noddy constructs a nest. It is thought that the reason for the absence of nests is the reduction in nest parasites, which in some colonial seabirds can cause the abandonment of an entire colony. In spite of these benefits there are costs associated with tree nesting, as the eggs and chicks are vulnerable to becoming dislodged by heavy winds. For this reason the white tern is also quick to relay should it lose the egg. The newly hatched chicks have well developed feet with which to hang on to their precarious nesting site. It is a long-lived bird, having been recorded living for 42 years.
保护状况
- 种群趋势
- stable
照片
分布
鸟叫声
其他鸟类
Long-billed Crombec
Sylvietta rufescens
A tiny, rotund, virtually tailless warbler with buff-orange underparts, gray-brown upperparts, and a dark eye-stripe that forms a buffy eyebrow. Pairs often join mixed-species flocks actively hopping along branches, occasionally hanging like mini-nuthatches, searching for invertebrates, and occasionally eating plant matter. Occupies broadleaf woodland, savanna, and arid scrub, where it is often detected by its quiet but distinctive faltering “chree-chirrit, chree-chirrit, chree-chirrit” song. The Red-capped Crombec has paler light gray upperparts and lacks the Cape Crombec’s eye-stripe, giving it a more open tawny face.
Cassia Crossbill
Loxia sinesciuris
Stocky, large-headed finch with unique crossed bill used to pry seeds out of lodgepole pine cones. Similar to Red Crossbill, best separated by voice, specifically the flight calls given in flight, a comparatively lower frequency, dry "dip-dip-dip". Endemic to Albion Mountains and South Hills of southern Idaho. Males are dull red or orange overall with gray or brown highlights. Females are dull olive-yellow. Immatures are streakier than adults. Sedentary, unlike most other crossbills. Often in small flocks. Rarely visits feeders.
Short-tailed Drongo
Dicrurus striatus
Glossy drongo of the eastern Visayas and Mindanao. Note the blue iridescence on the wings and neck, as well as the relatively weakly forked tail. Similar to Philippine Drongo-Cuckoo, but note present species’ much heavier bill. A vocal inhabitant of forested habitats, often foraging actively from exposed perches, sometimes in pairs or small groups. Vibrant song consists of clicks, whistles, warbles, harsh grating notes, and mimicry.
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