Mallard - Description

Description

The Mallard is a medium-sized waterfowl species, although is often slightly heavier than most other dabbling ducks. It 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). Among standard measurements, the wing chord is 25.7 to 30.6 cm (10.1 to 12.0 in), the bill is 4.4 to 6.1 cm (1.7 to 2.4 in) and the tarsus is 4.1 to 4.8 cm (1.6 to 1.9 in). The breeding male Mallard is unmistakable, with a glossy bottle-green head and white collar which demarcates the head from the purple-tinged brown breast, grey brown wings, and a pale grey belly. The rear of the male is black, with the dark tail having white borders. The bill of the male is a yellowish orange tipped with black while that of the female is generally darker ranging from black to mottled orange. The female Mallard is predominantly mottled with each individual feather showing sharp contrast from buff to very dark brown, a coloration shared by most female dabbling ducks, and has buff cheeks, eyebrow, throat and neck with a darker crown and eye-stripe. Both male and female Mallards have distinct iridescent purple blue speculum feathers 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 characteristic 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).