White-backed Duck
Thalassornis leuconotus
A smallish, tawny, bulbous-headed duck that sits low in the water, its tail often flush with the surface, giving it a distinctive appearance. When seen well, the white patch at the base of the bill is diagnostic. The namesake white back is usually visible only in flight. Partially nomadic; small groups are found on pans and pools that have emergent aquatic vegetation, especially waterlilies. Mostly quiet; rarely gives a squeaky-toy-like “swit-swit” whistle.
识别特征
These birds are well adapted for diving. On occasions they have been observed to stay under water for up to half a minute. They search especially for the bulbs of waterlilies, but also seeds and leaves of waterlilies and other water plants and the young feed on lake flies larvae as well. From danger, they also escape preferentially by diving; hence, the namesake white back is hardly visible in life.
分类信息
- 学名
- Thalassornis leuconotus
- 命名信息
- Eyton, 1838
- 目
- Anseriformes
- 科
- Anatidae
- 属
- Thalassornis
分布与栖息地
White-backed ducks live in Africa, especially between Senegal and Chad in the west, Ethiopia in the east, and South Africa in the south. Their habitat consists of lakes, ponds, swamps and marshes where they are well camouflaged against predators.
- 迁徙
- Resident species
保护状况
The white-backed duck is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.<p>Woolaver and Nichols conducted a nesting survey of the Madagascar race in 2001 at Lake Antsamaka in western Madagascar. They found a total of 37, indicating the significance of this single site for the conservation of this insular subspecies. Young, et al. (2006) suggested that an earlier population estimate of 2,500–5,000 total birds in Madagascar by Delany and Scott may be too optimistic. Its African population may be in the range of 10,000 to 25,000 birds.
- 种群趋势
- declining
照片
分布
其他鸟类
Cape Verde Swift
Apus alexandri
Small endemic swift of Cape Verde. Smaller and more gray-brown compared to other swifts, with prominent whitish throat patch. Note shallow forked tail. Flight faster and more fluttering than Common Swift and the closely-related Plain Swift. Calls very similar to Common Swift, but slightly higher-pitched.
Madagascar Cuckoo-Hawk
Aviceda madagascariensis
Rather nondescript, brown mid-sized raptor. Endemic to Madagascar, where it is found in and around all forest types. Sometimes soars. Extremely similar to Madagascar Buzzard. In flight, Madagascar Cuckoo-Hawk is distinguished by the heavy barring across the whole underwing and by the fewer thicker dark bars on the tail. When perched, look for the small, round head with a bulging eye. Madagascar Cuckoo-Hawk also usually shows a heavily barred chest and white belly, whereas Madagascar Buzzard shows the opposite.
Welcome Swallow
Hirundo neoxena
Small swallow with long forked tail. Dark above, pale below, with a rusty breast and face. In Australia, much less common Barn Swallow has a dark chest band and is much paler below, including parts of the underwing. Common bird across open habitat, where it feeds on insects above parks, sporting fields, wetlands, and other open areas. Perches on fence rows and utility lines in large numbers.
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