Birds
Duck
Anatidae · also called ducks
A duck is the small, familiar end of the waterfowl family — the bird on the park pond, upending in the shallows with its tail in the air. Behind that ordinariness sits a set of real specialisations: a bill that filters food out of mud, feathers engineered to shed water, and a breeding system in which the bright drake usually leaves the drab hen to raise the brood alone.
Overview
Ducks are the smaller members of the waterfowl family Anatidae, on every continent except Antarctica. The main groups are the dabbling ducks (mallard, teal, wigeon) that feed at the surface and upend in the shallows, the diving ducks (pochard, scaup, eider) that dive for food, and the fish-eating mergansers with narrow serrated bills. Most are omnivores.
The bill
A duck’s bill carries rows of comb-like plates, the lamellae, and the bird pumps water and mud through it with its tongue, trapping seeds, invertebrates, and plant fragments while the water drains out the sides.
Bright drakes, hidden hens
In many ducks the drake is boldly patterned and the hen mottled brown for camouflage, and the pair bond usually ends at incubation, leaving the female to raise the brood. Ducklings hatch ready to go — walking, swimming, and feeding within hours — and tree-nesting wood ducks leap from the nest hole on their first day. Ducks are also one of the few bird groups in which males have a penis, corkscrew-shaped and sometimes body-length in a coevolutionary arms race with female anatomy.
Status
Ducks as a family are Not Evaluated. Most northern species are abundant, helped by wetland protection funded partly by hunting licences, but the Madagascar pochard is Critically Endangered (rediscovered in 2006), the white-headed duck is threatened by hybridisation with introduced ruddy ducks, and several tropical and island species are declining from habitat loss.
Duck: common questions
What is the difference between a duck, a goose, and a swan?
All three are in the waterfowl family Anatidae and grade into one another by size and proportion. Ducks are the smallest and most varied, with short necks, and in many species the male and female look strikingly different, with the female usually raising the brood alone. Geese are intermediate, with longer necks, stouter forward-set legs for grazing on land, no strong plumage difference between the sexes, and pair bonds that last for years. Swans are the largest, with very long necks, all-white adults in the northern species, and long pair bonds with both parents tending the young. The boundary is not sharp, and a few birds sit awkwardly between the groups.
Why do male and female ducks look so different?
It comes from the split in what each parent does. In most ducks the pair bond ends once the female starts incubating, so the male plays no part in raising the young and is free to compete for mates through bright, showy plumage, which females use to judge his quality. The female, by contrast, sits exposed on a ground nest for a month and then leads vulnerable ducklings around open water, so she is under strong pressure to be camouflaged, which is why hens of so many species are mottled brown. In species where the male does help with the brood, such as the whistling ducks and shelducks, the sexes look much more alike.
Can ducks feel cold on ice and in freezing water?
Their feet are barely affected, thanks to a heat-exchange system. The arteries carrying warm blood down to a duck's feet run right alongside the veins carrying cool blood back up, so heat passes across from one to the other, and the blood returning to the body is rewarmed while the feet are kept just above freezing. This means very little body heat is lost through the feet, the feet themselves have few nerves and little fluid to freeze, and a duck can stand on ice or paddle in near-freezing water without discomfort. The dense, oiled, air-trapping feather coat keeps the rest of the body warm.
Is it bad to feed ducks bread?
Yes, in more than one way. Bread is low in the protein, vitamins, and minerals ducks need, so a diet heavy in bread can cause poor growth and a wing deformity called angel wing in ducklings. Uneaten bread rots in the water, fuelling algae and bacteria and lowering oxygen, which harms fish and the ducks themselves. Large handouts also draw unnaturally dense flocks that spread disease and foul the area, and they make wild ducks dependent and bold. If you want to feed ducks, better options are defrosted peas or sweetcorn, chopped lettuce, oats, or proper waterfowl pellets, given in small amounts away from crowded spots.