Behaviour This species is highly migratory, breeding widely across Western Eurasia and wintering within the northern tropics¹⁶. It migrates on a broad front, the autumn migration beginning in late July and peaking in August or early September (in Europe and Egypt), with birds beginning to arrive in East and West Africa in early September, peaking in October¹⁶. Once the species reaches Africa it migrates in relation to seasonal flooding, the central point of its occurrence shifting gradually along the course of rivers as the winter progresses¹⁷. The spring migration begins in February, with birds beginning to arrive on breeding grounds from mid-March to early-May¹⁶. It is a highly sociable and gregarious species^{3, 4}, and whilst breeding can be found in single pairs or small groups, but regularly forms large congregations of several hundred on passage, and flocks of up to several thousand are common in African and Asiatic winter quarters^{3, 4}. Adults undergo a post-breeding moult period that leaves them flightless for 3-4 weeks, with males moulting between mid-July and mid-August, and females between mid-August and September^{4, 5}. The Volga Delta, in particular, is a major moulting area for this species¹⁵. Birds of this species are both diurnal and nocturnal feeders, and when migrating often travel by night and rest on open water during the day¹. Habitat Breeding In the breeding season this species frequents small, shallow ponds and lakes with abundant floating, emergent and fringing vegetation^{1, 2} (that is not too tall or dense, such as bulrush - Typha spp.)^{4, 10}, in grass dominated environments, like swampy meadows, flooded fields, shallow freshwater marshes^{1, 2, 18}. Non-breeding During this season the species shows a preference for large freshwater or occasionally brackish lakes, again with abundant floating, emergent and fringing vegetation⁵, also shallow flood plains, shallow dams, pans and sewage ponds (in South Africa)¹¹. The species also frequents coastal saltmarshes and lagoons on passage² and may spend the day resting on marine inshore waters when migrating³. Diet Breeding When breeding this species is omnivorous¹. In spring and summer its diet is dominated by animal matter: chiefly molluscs, aquatic insects and their larvae (waterbugs, caddisfly, waterbeetles, midges), crustaceans (ostracods and phyllopods especially), worms, leeches, young and spawn of frogs, and small fish^{1, 11}. Seeds, roots, tubers, stems, leaves and buds of plants such as Hornwort Ceratophyllum, Naiad Najas, sedge, grass and other aquatic plants are also important at this time^{1, 2, 4}. Non-breeding During this season the birds are mainly vegetarian, with a diet dominated by the seeds of pondweeds, smartweeds Polygonum, sedges, dock Rumex, wild rice and grass⁵, (with the seeds of Echinochloa colona, Nymphea micranthia and Nymphea lotus being the most preferred food items)¹⁹. Breeding site Meadows are the favoured nesting areas of this species, with nests rarely located more than 150 m from water (usually within 20 m)⁴. The nest itself is a depression in the ground, typically situated under rushes or tall grasses (such as manna grass, Glyceria), but not generally under shrubs^{1, 2}.

TCTATACCTTATCTTCGGGGCATGAGCCGGAATAATTGGCACAGCACTAAGCCTACTAATCCGCGCAGAACTTGGTCAACCAGGAACCCTCCTGGGCGATGACCAAATTTACAACGTGATCGTCACCGCTCACGCCTTTGTAATAATTTTCTTCATAGTAATGCCCATCATAATTGGGGGATTTGGCAACTGATTGGTCCCCCTGATAATCGGTGCCCCCGACATAGCATTCCCACGAATAAATAACATAAGCTTCTGACTCCTTCCACCATCATTCCTTCTACTACTCGCCTCATCTACCGTAGAAGCTGGCGCTGGCACAGGTTGAACCGTGTACCCGCCCCTAGCAGGCAACCTAGCCCATGCCGGGGCATCAGTAGACCTGGCCATTTTCTCACTCCACCTAGCCGGTGTTTCCTCCATCCTTGGAGCCATTAACTTCATTACCACAGCCATCAACATAAAACCCCCTGCACTCTCACAGTACCAAACCCCACTTTTCGTCTGATCAGTCCTAATTACCGCCATCCTGCTCCTCCTGTCACTTCCTGTCCTTGCCGCCGGCATTACAATGCTGCTAACCGACCGGAACCTAAACACTACATTCTTTGACCCTGCCGGAGGAGGAGACCCGATCCTGTACCAACACCTATTTTGATTCTTCGGCCACCCAGAAGTTTATATCTTAATTCTT
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Breeding The most significant threat encountered by this species on its breeding grounds in Europe is habitat deterioration through the drainage and reclamation of wetlands⁵, the increasing climatic aridity and subsequent lowering of the water table, and the transformation of wetlands to dammed reservoirs¹⁶. Other threats to this species include the destruction of nests during the early mowing of meadows⁵, increased human disturbance⁵, lead poisoning, botulism during hot summers⁵ and hunting disturbance in Africa and Europe⁷ (> 500,000 are shot annually in Russia, Ukraine, France and Poland)⁵. The invasive species American Mink Mustela vison also poses a threat through nest predation⁶, and the species is susceptible to avian influenza (particularly strain H5N1) so is therefore threatened by outbreaks of the virus¹². Non-breeding On its wintering grounds in Nigeria and Senegal the species is threatened by habitat destruction through dam construction, vegetation overgrowth and desertification^{2, 8, 9}, and in West Africa it is threatened by large-scale river diversion and irrigation schemes¹⁶. The species is also at risk from avain influenza in its African wintering grounds²¹ as well as in its breeding areas¹². The proportion of the species which migrates via the West Siberian flyway is susceptible to West Nile Virus, and is therefore threatened by future outbreaks²⁰. Utilisation This species is hunted in Denmark , but there is evidence that this may be sustainable¹³. The species is also hunted for commercial and recreational purposes in Gilan Province, northern Iran²².