Waterfowl | Anseriformes

Eendachtigen | Waterfowl | Anseriformes

Water birds whose whole build, in the ducks, geese and swans (Anatidae), is tuned to water: a buoyant body, short legs set well back and three front toes joined by webbing, which makes walking on land a waddle. The bill is flattened and carries rows of horny lamellae along its edges; its soft skin is packed with touch corpuscles, so food is found by feel in turbid water and in mud, and is sieved or sheared off with the serrated tongue. Beneath the contour feathers lies a thick layer of down, and the whole plumage is kept water-repellent with oil from a large preen gland. The flight feathers are not shed one by one but all at once, so each year there are several weeks in which the birds cannot fly and withdraw to safe open water. The young are nest-leavers, downy and open-eyed, feeding themselves from the first day; the male has, exceptionally among birds, an eversible intromittent organ. The screamers (Anhimidae) of marshes and riverbanks in the lowlands east of the Andes differ sharply: they have a short, chicken-like bill without lamellae, only traces of webbing, two sharp spurs on each wing and no intromittent organ.

Famílias desta ordem

Screamers | Anhimidae3 espéciesThree species in two genera occur in this guide, all in the lowlands at the foot of the Andes: the Horned Screamer in marshes, oxbow lakes and riverbanks of the Amazon basin, the Northern Screamer in the wet lowlands of northern Colombia and the Southern Screamer in the flooded savannas of eastern Bolivia. Screamers are related to ducks and geese, but with their small, fowl-like bill, bulky body and long, barely webbed toes they look more like a giant chicken. The leading edge of each wing carries two sharp spurs, used in fights over territory. Beneath the skin lies a layer of small air sacs, so that the body crackles when touched. The Horned Screamer also bears a long, thin horn-like projection on the forehead. They graze on aquatic plants and leaves, walk over floating vegetation and, despite their weight, sometimes soar high on thermals. The voice is a loud, trumpeting call that pairs give in duet and that carries for kilometres. The nest is a heap of plant material in or beside the water, and the young leave it soon after hatching.
Ducks, swans and geese | Anatidae39 espéciesIn this guide the family numbers 39 species in twenty genera. The length of the neck decides how a species reaches its food: grazing on short waterside growth, sieving at the surface, upending with the tail in the air, or diving to the bottom — on a single Andean lake or coastal lagoon these methods often occur side by side. Besides the true ducks the family holds goose-like forms with long legs and an upright stance, such as the Andean Goose that grazes the boggy grasslands of the puna and the Orinoco Goose of riverbanks in the lowlands at the foot of the Andes, as well as whistling ducks that are active mainly at dusk and by night and take their name from the clear flight call, and stiff-tails that lie low in the water and display with the tail cocked. Peculiar to the Andes is the Torrent Duck, which swims upstream in fast mountain rivers and dives among the boulders of the rapids for insect larvae. Unlike the ducks of the northern temperate zone, in many resident species here the sexes differ little or not at all and there is no eclipse plumage; the distinctions then lie in bill and eye colour, in the size of a knob, and in the pattern of the speculum. Nests are a scrape lined with the female's own breast down among waterside vegetation, a tree hole or a rock crevice; in most species the female incubates alone and leads the downy young, while in whistling ducks both parents share incubation. The young feed themselves from the first day.