Habitat and Ecology
Behaviour This species is strongly migratory throughout its northern range1, 2 although some populations in the Southern Hemisphere are sedentary1. It breeds in solitary pairs or loose groups1 from April to June3, with males leaving the breeding areas first from May to early-June to undertake extensive moult migrations (females following later)5. During moult, large sexually segregated3 flocks gather in moulting areas2 (e.g. in the Netherlands and Russia), although small gatherings are also possible5. The flightless moult period lasts for around 4 weeks4, 5 between July and August5 after which flocks move southwards to winter quarters from mid-August onwards3, 5. The species is highly gregarious in winter and on passage, often forming enormous concentrations3, 5 (although the size of flock depends on the size of the wetland)7. It feeds nocturnally6, 8, flocks roosting by day on open water6. Habitat The species shows a preference for open lowland grassland7, prairie or tundra habitats4 containing freshwater, brackish and saline wetlands with shallow water (10-30 cm deep7) to facilitate dabbling2. Wetland habitats include shallow freshwater marshes1, 4, 8, small marshy lakes, slow-flowing rivers1, 3, 4, 8, wet meadows3, flood-plains and sewage ponds (southern Africa)8, especially favouring ponds with low, dense marginal vegetation and wetlands interspersed with brushy thickets or copses4. During the winter it also frequents large inland lakes5, brackish coastal lagoons1, 3, 5, brackish3 and saline marshes18, shallow fresh or brackish estuaries4, 6, 7, tidal flats3 and river deltas5 with adjacent agricultural land (e.g. stubble fields7) and scattered impoundments4. Diet This species is omnivorous1 and opportunistic4, its diet consisting of algae6, seeds8 (e.g. cereals1 and rice6), tubers (e.g. potatoes)1, 6, 8, and the vegetative parts of aquatic plants, sedges1, 8 and grasses6, 8, as well as aquatic invertebrates (e.g. insects, molluscs and crustaceans), amphibians1, 6, 8 and small fish1. Breeding site The nest is a slight hollow on the ground amongst vegetation1 (e.g. rushes, grass or low scrub) and can be close to or more than 1 km away from water2, 7. The species is not normally colonial but neighbours may nest as close as 2-3 m apart2.