Knob-billed Duck
Sarkidiornis melanotos
Large bicolored waterbird. Both sexes are iridescent purplish-green above with a white or buffy breast. Males have a large black lump on the bill, gray flanks and whitish belly, whereas females have a plain bill and gray flanks. Note all dark wings. Occurs throughout much of Africa, India, and Southeast Asia. Found in freshwater rivers, lakes, and marshes where it is usually uncommon. Normally silent.
识别特征
This common species is unmistakable. It is one of the largest species of duck. Length can range from 56 to 76 cm (22 to 30 in), wingspan ranges from 116 to 145 cm (46 to 57 in) and weight from 1.03 to 2.9 kg (2.3 to 6.4 lb). Adults have a white head freckled with dark spots, and a pure white neck and underparts. The upperparts are glossy blue-black upperparts, with bluish and greenish iridescence especially prominent on the secondaries (lower arm feathers). The male is much larger than the female, and has a large black knob on the bill. Young birds are dull buff below and on the face and neck, with dull brown upperparts, top of the head and eyestripe. Knob-billed ducks are generally larger in size when compared to comb ducks, and flanks are usually lighter (light grey, in females sometimes whitish).<p>Immature knob-billed ducks look like a large greyish female of the cotton pygmy goose (Nettapus coromandelicus) and may be difficult to tell apart if no other birds are around to compare size and hue. However, knob-billed ducks in immature plumage are rarely seen without adults nearby and thus they are usually easily identified too.<p>The knob-billed duck is silent except for a low croak when flushed.
分类信息
Uncertainty surrounds the correct systematic placement of this species. Initially, it was placed in the dabbling duck subfamily Anatinae. Later, it was assigned to the "perching ducks", a paraphyletic assemblage of waterfowl most of which are intermediate between dabbling ducks and shelducks. As the "perching ducks" were split up, the knob-billed duck was moved to the Tadorninae or shelduck subfamily.<p>Analysis of mtDNA sequences of the cytochrome b and NADH dehydrogenase subunit 2 genes, however, suggests that it is a quite basal member of the Anatidae, vindicating the earliest placement. But its closest living relatives cannot be resolved to satisfaction without further study.
- 学名
- Sarkidiornis melanotos
- 命名信息
- (Pennant, 1769)
- 目
- Anseriformes
- 科
- Anatidae
- 属
- Sarkidiornis
分布与栖息地
- 迁徙
- Complete migrants
行为
It breeds in still freshwater swamps and lakes in the tropics. It is largely resident, apart from dispersion in the wet season.<p>This duck feeds on vegetation by grazing or dabbling and to a lesser extent on small fish, invertebrates, and seeds. It can become a problem to rice farmers. Knob-billed ducks often perch in trees. They are typically seen in flocks, small in the wet season, up to 100 in the dry season. Sometimes they separate according to sex.<p>The knob-billed duck is declining in numbers locally, but due to its wide range it is not considered globally threatened by the IUCN. It is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds applies.<p>African birds breed during and after the rainy season and may not breed if the rain is scanty. Knob-billed ducks nest mainly in tree holes, also in tall grass.<p>Males may have two mates at once or up to five in succession. They defend the females and young but not the nest sites.<p>Females lay 7 to 15 yellowish-white eggs.
保护状况
- 种群趋势
- declining
照片
分布
鸟叫声
其他鸟类
Malayan Crestless Fireback
Lophura erythrophthalma
A rare, compact pheasant of damp tropical lowland rainforest, especially peat swamp forest. Dark overall with bright red facial skin and a cocked, vertically-flattened tail. Males have fine vermiculations on the wings, deep orange (fire)back, purple rump and pale orange tail. Females are dark blue all over. Exceedingly shy, typically moving in pairs or small groups. Female is similar to Salvadori’s Pheasant male but the 2 species do not normally co-occur and the latter has often has its tail pointing downwards. Gives a relatively high-pitch “chick!” followed by a low “takrow”.
Yellow-billed Oxpecker
Buphagus africanus
A bulbul-sized olive-brown bird that sports a diagnostic red-tipped yellow bill, a red eye without an eye-wattle, and a pale buff rump. The juvenile lacks the bright bill and eye coloration but shows the pale rump. Small groups occur in savanna and farmland, where they require large wild ungulates and domestic stock to forage on; they clamber agilely over host mammals, gleaning ticks, mites and other ectoparasites, and occasionally drinking host blood. As they fly between large mammals, they give a distinctive sizzling-crackle call. The similar Red-billed Oxpecker differs from Yellow-billed Oxpecker by having a red bill, a yellow eye-wattle, and a dark rump the same color as the remainder of the upperparts.
Pied Imperial-Pigeon
Ducula bicolor
Robust, gregarious, and black-trimmed large white pigeon. Inhabits coastal forests on small offshore islands, only making occasional forays to mainland areas to forage and to roost. Often perches high on the bare branches of trees or on power/telephone lines; often found in flocks of ten or more. Song is very low in pitch and includes “woo-oo-woooo,” with the last syllable drawn out; loud at first and then trailing off. Compare with Silver-tipped and Torresian Imperial-Pigeons where overlap exists; no similar species in introduced range in the Caribbean.
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