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## Mallard

### Anas platyrhynchos

The Mallard, or Wild Duck is a dabbling duck which breeds throughout the temperate and subtropical Americas, Europe, Asia, and North Africa, and has been introduced to New Zealand and Australia.
The male birds have a bright green or blue head, while the female's is light brown. The Mallard lives in wetlands, eats water plants, and is gregarious. The Mallard is the ancestor of most domestic ducks, and can interbreed with other species of genus Anas. Among close relatives of the Mallard this hybridisation can cause genetic dilution, which is contributing to the decline of rarer species of ducks.`n`nThe Mallard is 50-65 cm (20-26 in) long (of which the body makes up around two-thirds), has a wingspan of 81-98 cm (32-39 in), and weighs 0.72-1.58 kg (1.6-3.5 lb). The breeding male is unmistakable, with a bright bottle-green head, black rear end and a yellowish orange (can also contain some red) bill tipped with black (as opposed to the black/orange bill in females). It has a white collar which demarcates the head from the purple-tinged brown breast, grey brown wings, and a pale grey belly. The dark tail has white borders. The female Mallard is a mottled light brown, like most female dabbling ducks, and has buff cheeks, eyebrow, throat and neck with a darker crown and eye-stripe. However, both the female and male Mallards have distinct purple speculum edged with white, prominent in flight or at rest (though temporarily shed during the annual summer moult). Upon hatching, the plumage colouring of the duckling is yellow on the underside and face (with streaks by the eyes) and black on the backside (with some yellow spots) all the way to the top and back of the head. Its legs and bill are also black. As it nears a month in age, the duckling's plumage will start becoming drab, looking more like the female (though its plumage is more streaked) and its legs will lose their dark grey colouring. Two months after hatching, the fledgling period has ended and the duckling is now a juvenile. Between three to four months of age, the juvenile can finally begin flying as its wings are fully developed for flight (which can be confirmed by the sight of purple speculum feathers). Its bill will soon lose its dark grey colouring and its sex can finally be distinguished by three factors. The bill colouring is yellow in males, black and orange for females. The breast feathers are reddish-brown for males, brown for females. The centre tail feather is curled for males (called a drake feather), straight for females
During the final period of maturity leading up to adulthood (6-10 months of age), the plumage of female juveniles remains the same while the plumage of male juveniles slowly changes to its recognizable colours. This plumage change also applies to adult Mallard males when they transition in and out of their non-breeding (eclipse) plumage at the beginning and the end of the summer moulting period. The adulthood age for Mallards is 14 months and the average life expectancy is 20 years.
Several species of duck have brown-plumaged females which can be confused with the female Mallard. The female Gadwall (A. strepera) has an orange-lined bill, white belly, black and white speculum which is seen as a white square on the wings in flight, and is a smaller bird. More similar to the female Mallard in North America are the American Black Duck (A. rubripes), which is notably darker hued in both sexes than the Mallard, and the Mottled Duck (A. fulvigula), which is somewhat darker than the female Mallard, with no white edge on the speculum and slightly different bare-part coloration.
In captivity, domestic ducks come in wild-type plumages, white, and other colours. Most of these colour variants are also known in domestic Mallards not bred as livestock, but kept as pets, aviary birds, etc., where they are rare but increasing in availability.
A noisy species, the male has a nasal call, and a high-pitched whistle, while the female has a deeper quack stereotypically associated with ducks.
The Mallard is a rare example of both Allen's Rule and Bergmann's Rule in birds. Bergmann's Rule, which states that polar forms tend to be larger than related ones from warmer climates, has numerous examples in birds. Allen's Rule says that appendages like ears tend to be smaller in polar forms to minimize heat loss, and larger in tropical and desert equivalents to facilitate heat diffusion, and that the polar taxa are stockier overall. Examples of this rule in birds are rare, as they lack external ears. However, the bill of ducks is very well supplied with blood vessels and is vulnerable to cold.
Due to the malleability of the Mallard's genetic code, which gives it its vast interbreeding capability, mutations in the genes that decide plumage colour are very common and have resulted in a wide variety of hybrids such as Brewer's Duck (Mallard - Gadwall, Anas strepera).