The Mallard, Anas platyrhynchos, also known in North America as the Wild Duck, is a common and widespread dabbling duck which breeds throughout the temperate and sub-tropical areas of North America, Europe and Asia. It also frequents Central America and the Caribbean. It is probably the best-known of all ducks.
This dabbling duck is 56-65 cm length, with a 81-98 cm wingspan, and weighs 750-1000 g. It is is strongly migratory in the northern parts of its breeding range, and winters farther south. It is highly gregarious outside of the breeding season and will form large flocks.
The breeding male is unmistakable, with a green head, black rear end and a blue speculum edged with white, obvious in flight or at rest. Males also possess a yellow bill with a black tip, whereas females have a dark brown bill.
The females are light brown, with plumage much like most female dabbling ducks. They can be distinguished from other ducks, by the distinctive speculum. In non-breeding (eclipse) plumage, the drake looks more like the female.
It is a bird of most wetlands, including parks, small ponds and rivers, and usually feeds by dabbling for plant food or grazing. It nests usually on a river bank, but not always particularly near water.
This is a noisy species. The male has a nasal call, whereas the female has the very familiar "quack" always associated with ducks.
Mallards frequently interbreed with the American Black Duck, Northern Pintail and domesticated species, leading to various hybrids. A Mallard has been recorded as living for 29 years.
The Greenland Mallard is one of the rare examples of both Allen's Rule and Bergmann's Rule in birds. Bergmann's Rule - polar subspecies/species tend to be larger than related ones from warmer climates - has numerous examples in birds, but examples of Allen's Rule - appendages like ears tend to be smaller in polar subspecies/species to minimize heat loss and large in tropical and desert equivalents to faciliate heat diffusion, and the polar taxa are stockier overall - are rare, as birds don't have ears (where Allen's Rule manifests most prominently). However, the bill of ducks is very well supplied with blood vessels and vulnerable to cold. Thus, the Greenland Mallard, although considerably larger than the nominate subspecies, has a smaller bill and is stockier.