Black Swan vs Knob-billed Duck
Cygnus atratus compared with Sarkidiornis melanotos
Side-by-Side Comparison
| Attribute | Black Swan | Knob-billed Duck |
|---|---|---|
| Scientific Name | Cygnus atratus | Sarkidiornis melanotos |
| Order | Anseriformes | Anseriformes |
| Family | Anatidae | Anatidae |
| Conservation Status | Least Concern | Least Concern |
| Length | 130.0 cm (51.2 in) | — |
| Wingspan | 190.0 cm (74.8 in) | 64.2 cm (25.3 in) |
| Weight | 6200.0 g (218.70 oz) | 1817.5 g (64.11 oz) |
| Diet | Aquatic vegetation and algae, supplemented with grain and pasture grasses. Feeds by upending in shallow … | Dabbles for seeds and aquatic invertebrates; diet shifts toward invertebrate prey in spring breeding season; … |
| Clutch Size | 4-6 | 6-20 |
| Population Trend | — | — |
Size Comparison
Habitat Comparison
Black Swan
Lakes, rivers, swamps, and coastal waters across Australia. Also found in ornamental lakes in parks.
Knob-billed Duck
Freshwater lakes, marshes, floodplains, and forested wetlands across sub-Saharan Africa and South and Southeast Asia from India to southern China. Nests in large tree hollows near water.
Song & Call Comparison
Black Swan
Gives a musical bugling 'boo-boo-boo' in flight and softer honking on water. Less vocal than Mute Swan; produces a baying call when alarmed. Wings whistle softly in flight.
Knob-billed Duck
A low, grunting 'wuk' or soft, nasal 'krank'. Similar to Comb Duck in call quality. Generally quiet; calls are not loud or distinctive compared to other large African waterfowl.
Geographic Range & Migration
Black Swan
Australia, primarily in the southeast and southwest. Introduced populations in New Zealand, Japan, and western Europe.
Knob-billed Duck
Breeds on sub-Arctic tundra; winters on the Atlantic coast of North America from Labrador to Florida and the Gulf Coast.
Conservation Status
Black Swan
Knob-billed Duck
How to Tell Them Apart
Black Swan
Almost entirely black with white flight feathers visible in flight. Red bill with a white band near the tip. Dark red to reddish-brown iris.
Bright red bill with a pale tip and prominent white band
Knob-billed Duck
Males have white head with black spots; iridescent dark blue-black back and wings; white underparts with gray flanks. Large black fleshy knob atop bill. Females smaller, brown, and lack the …
About These Birds
Black Swan
The black swan was once considered impossible by Europeans who believed all swans were white, making it a famous philosophical example of inductive reasoning failure. It is the state emblem of Western Australia. Black swans form lifelong pair bonds and both parents share in incubation and care of cygnets.
Knob-billed Duck
Old World equivalent of the Comb Duck, with iridescent black-and-white body and the male's distinctive bill knob. Found across sub-Saharan Africa and South Asia. Uses tree cavities for nesting. Gregarious outside breeding season; forms large flocks at seasonal wetlands.