Black-headed Duck vs Brazilian Merganser
Heteronetta atricapilla compared with Mergus octosetaceus
Side-by-Side Comparison
| Attribute | Black-headed Duck | Brazilian Merganser |
|---|---|---|
| Scientific Name | Heteronetta atricapilla | Mergus octosetaceus |
| Order | Anseriformes | Anseriformes |
| Family | Anatidae | Anatidae |
| Conservation Status | Least Concern | Critically Endangered |
| Length | — | — |
| Wingspan | 34.7 cm (13.7 in) | 39.2 cm (15.4 in) |
| Weight | 528.5 g (18.64 oz) | 827.6666666666666 g (29.20 oz) |
| Diet | Parasitic; adults may feed on aquatic plants, seeds, and invertebrates in South American marshes. Diet … | Dives for small fish in fast-flowing South American rivers. Critically endangered; uses serrated bill to … |
| Clutch Size | 2 | 5-8 |
| Population Trend | — | — |
Habitat Comparison
Song & Call Comparison
Black-headed Duck
Male gives a soft, raspy peeping note; female produces a muted quack. An obligate brood parasite with reduced vocalizations; subdued calls suit its secretive lifestyle among Argentine reeds.
Brazilian Merganser
Male produces a harsh, rasping call; female gives a guttural, grunting series. Critically endangered; quiet vocalizations suit its secretive lifestyle in fast-flowing Brazilian mountain rivers.
Geographic Range & Migration
Black-headed Duck
Resident in southern South America from southern Brazil and Bolivia south to Argentina and Chile. Found on lakes and marshes in open lowlands.
Brazilian Merganser
Critically endangered; restricted to a few rivers in southern Brazil, Argentina, and Paraguay. Found on fast-flowing rivers in Atlantic Forest.
Conservation Status
Black-headed Duck
Brazilian Merganser
How to Tell Them Apart
Black-headed Duck
Male has distinctive jet-black head and neck, warm chestnut-brown back, and pale buff underparts; blue-grey bill with red base. Female is streaked brown above with pale supercilium and whitish underparts.
Brazilian Merganser
Male has dark glossy greenish-black head with long shaggy crest; finely vermiculated grey body, white wing patch. Female similar but with rufous-chestnut wash on head and shorter crest.
About These Birds
Black-headed Duck
A small diving duck (~530 g) of South America, family Anatidae, and the sole member of genus Heteronetta. Inhabits freshwater marshes and lakes in Argentina, Bolivia, Brazil, Chile, and Uruguay. Unique among waterfowl as an obligate brood parasite, laying eggs in nests of coots and other waterbirds. Feeds on seeds and aquatic invertebrates. Least Concern.
Brazilian Merganser
One of the world's rarest waterfowl (~830 g), family Anatidae, with a serrated bill and dark green head with bushy crest. Inhabits fast-flowing clear rivers in the Atlantic Forest of Brazil, Argentina, and Paraguay. Feeds on fish and aquatic invertebrates. Critically Endangered; fewer than 250 mature individuals remain due to dam construction and river degradation.