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35–42 cm; male 770–910 g, female 455–790 g, unsexed 363–1236 (737) g; wingspan 75–85 cm. Differs from F. atra in overall slightly darker appearance , no white tips to secondaries, rounded projection of loral feathering between bill and shield, red knobs at top of frontal shield . Sexes alike, but female smaller. Non-breeding adult has small knobs (often very hard to see), red-brown iris, duskier tinge at sides of bill, and dull slate legs and feet. Immature like adult but feathers of chin, throat, breast and underparts fringed white; upperparts often have dusky olive tinge. Juvenile has crown and upperparts dark brown with olive tinge, sides of head, neck and flanks dark olive brown mottled off-white, lores, chin and throat white, and underparts pale ash grey; iris grey-brown to dark brown; bill dull grey; legs and feet dark grey.
S & E Spain (1) and N Morocco; Ethiopia, Eritrea, Kenya and Uganda S through Rwanda, Burundi, E DRCongo and Tanzania, W to Angola and S to South Africa; also Madagascar.
Chiefly frequents open fresh water of lakes , lagoons, ponds, permanent and temporary dams and vleis, and floodplains. Also occurs in swamps with reeds and papyrus, and at sewage ponds; sometimes found on rivers and tidal lagoons but generally prefers still water. When breeding, frequents waters with fringing or emergent vegetation, but at other times may occur on completely open waters; requires submerged aquatic vegetation for food. Habitat very similar to that of F. atra, which it replaces over most of range. Occurs up to 3000 m in E Africa.
Mainly sedentary; also nomadic and opportunistic. Local movements evident from degree of winter flocking, e.g. in Morocco, and from fluctuations in numbers on permanent waters throughout range. Erratic winter wandering beyond normal range reported in past from Morocco and Spain; in 19th century, when range extended to Algeria and Tunisia, wandered in winter to Portugal, S France, Sardinia, Sicily, Italy, and Malta. Flocks in Africa often sedentary on suitable waters but birds may move considerable distances outside breeding season, e.g. up to 1070 km in South Africa. At Barberspan, South Africa, factors influencing fluctuations include rainfall, water level and availability of favourite food; ringing recoveries show mean distance travelled from Barberspan 270 km, 70% recovered within 300 km; longest distances travelled Jan–Apr, when population drops during rainy season. Birds ringed Rondevlei, South Africa, disperse up to 400 km; birds ringed in Ngorongoro Crater, Tanzania, recovered at Eldoret and Naivasha, Kenya. On Kafue Flats, Zambia, present Feb–Oct, most Mar–Jun. Wanders to S Somalia.
Diet and Foraging
Omnivorous; takes mainly aquatic vegetation , especially non-rooting submerged or floating plants and including filamentous algae (Chlorophyceae), water plants such as Marsilia, Aeschynomene fluitans (stems, flowers, fruits and aerial roots), Polygonum limbatum (stems, leaves and fruits), Najas pectinata (stems and leaves), Potamogeton pectinatus, Ruppia maritima and Eichhornia crassipes, grass (e.g. leaves of Panicum repens) and seeds. Also eats molluscs (Gastropoda), crustaceans and arthropods (including insects), and occasionally carrion (e.g. ducks washed up on shore). Feeding techniques similar to those of F. atra, with emphasis on aquatic modes such as diving down and pulling up underwater vegetation; diving ability better developed than in F. atra; S of Sahara feeds mostly in water. Also feeds from surface , either while swimming or when standing in shallow water. Feeds much less often on land than does F. atra, but grazes short grass near water, especially when food scarce (bill has shearing edge adapted to grazing). On Kafue Flats, Zambia, grazes where vegetation trampled by lechwe (Kobus leche); in Natal, overgrazes green crops planted near dams.
Sounds and Vocal Behavior
Spain and N Africa, May; Morocco, Feb–Sept; Ethiopia, Apr–Jul, Sept–Dec; Kenya and NE Tanzania, all months; W Kenya and Uganda, all months except Feb; Zambia, Apr–Jul; Malawi, Jun–Jul; Zimbabwe, Jan–Sept; South Africa, all months; Madagascar, Dec–May. Gregarious outside breeding season but monogamous and territorial when breeding; some birds apparently also paired in winter flocks. Nest a bulky platform of leaves and stems of water plants; usually with ramp at one side; in shallow water, or floating and anchored to vegetation, built either in open water or within emergent vegetation, with no attempt at concealment. Both sexes build, occasionally with help of immatures; building renewed if platform settles or water rises; material also added during incubation. Builds many “false nests”, used as resting platforms. Normally 5–7 eggs (3–11), laid at daily intervals; 2 females known to have laid in 1 nest; incubation 18–25 days, by both sexes; hatching asynchronous; downy chick ashy or grey-black, paler below, with golden yellow down on neck, bare skin of crown pink and blue, down of mantle and back with white tips, iris brown, bill red with narrow white subterminal band, legs and feet pale grey-green with pink tinge; chicks precocial; leave nest after 1 day; able to dive soon after hatching, suggesting capability for independent feeding at early age; fed and cared for by both parents, sometimes with help of immatures from earlier brood, particularly when food and nesting habitat abnormally abundant; broods often divided between parents; fledging 55–60 days. In South Africa, 42% of nests produced fledged young. Often only 1 brood, unless conditions very favourable; possibly double-brooded in Morocco.
Not globally threatened (Least Concern). Range has decreased in both Europe and N Africa; now close to extinction in Europe; reasons for decline not clear. Locally common to abundant in sub-Saharan Africa, including Ethiopia, E Africa (L Victoria, L Naivasha and many highland dams and lakes), Zimbabwe, Namibia and Botswana; sometimes up to 27,000 birds at Barberspan and over 30,000 at de Hoop Vlei, South Africa; formerly common on Kafue Flats, Zambia. Uncommon in Angola, occurring mainly on coastal plain, and in Mozambique. In some areas, especially in South Africa and Zimbabwe, has benefited from the proliferation of farm dams and other artificial water bodies, especially as can breed on very small waters.