Maintenance of the plumage in an effective waterproof condition occupies much of the time not spent feeding or.... head displai

Bathing movements include dipping the head, beating the wings on the surface and, at high intensity, actual diving or somersaulting through the water. Formal aggressive displays are important in gregarious species to prevent actual fighting and injury and to establish instead a stable dominance order. Wing flaps and flicking of the folded wings are common in geese. The chin may be lifted during aggressive display, but more frequently the head is thrust forward, often with the bill open. The displays are well developed and characteristic of the species, which is necessary if mating with closely related and sympatric (coexistent) species is to be avoided. It is particularly striking in the dabbling ducks (Anatini), where it is often social, a group of males displaying around a solitary female, who appears to do the mate selection. Thus head-up-tail-up involves a simultaneous upward jerk of head and tail and a lifting of the folded wings to display the speculum, a set of metall! ic coloured secondary flight feathers of the upper wing. The grunt-whistle involves throwing an arc of water at the female by a sideways flick of the bill, followed by a rearing up of the body, shaking of the head and tail, and, during the whole sequence, giving the call indicated by the behavioural term. The sea ducks (Mergini) also have elaborate male displays, bowing while producing dovelike coos; flagging the head from side to side; jerking the head back on the tail and kicking up a spurt of water (the head-throw-kick of the goldeneye, ( Bucephala clangula ). The males cock their tails over their backs, inflate their lower necks, and beat on them with their bright blue bills, producing a chittering sound that terminates in a burp. Mutual preening and drinking displays are of this category, as are precopulatory displays, often ritualized feeding movements such as mutual head dipping, bill dipping, or head pumping. The geese and swans indulge in calling with upstretched n! ecks and lifted wings. The class of object is not necessarily ! treated as the sexual partner when the duck matures, but it does appear that male dabbling ducks learn the plumage patterns of the female from the ducks with which they are reared. Some nonvocal sounds are also produced by the wings of some species, by inflatable air sacs of others. head displai