image from, with caption:
(female mallard,left; male right)
(female mallard,left; male right)
Mallard ducks are a near-daily, and most pleasant, sight in Rock Creek Park (Northwest Washington, D.C.), where I pretend to "jog" (neighbors have congratulated me on my "walking") as regularly as I can.
Gentle-swimming ducks are seen mostly in the waters of the Creek (fast-flowing after rain, its current heading south), attractive, seemingly non-aggressive creatures creating caressing, triangular waves as they paddle along; they can be seen occasionally on land (and in the sky, stretching their wings) as well.
I was struck, while "jogging," how often these ducks appear in, on the surface, affectionate pairs -- even in group situations. Male/female. How tender and devoted, I thought, thinking that if one can assume another life after a short stay on planet Earth I would not mind being reincarnated as a male duck, with a gracious female companion (as I have for many years been blessed) to enjoy the waters (and the clouds and the soil beneath our feet) together on our minuscule corner of the universe.
(Speaking of feet, "Even common Mallard ducks attract your eyes with their construction-cone orange triangular webbed feet.)
As I bumped into a teacher of primary school children on an excursion in the park the other day, I told her: "The kids would love seeing the ducks. You can see them quite often around the bridge down the path."
But as I later read more about the ducks, I realized that, even in nature, nobody's perfect, including (especially?) male mallard ducks.
Sex War and Promiscuity: Why Ducks Have the Largest Penises in the World
Ducks are known to detain the record of penis size amongst vertebrates, compared to their own size: a specimen of Argentine blue-bill duck had a remarkable 42.5 cm (17 inches) long penis at a body length of 20 cm! (Could you imagine a 6 ft (1.8 m) tall man having a 13.3 ft (4 m) long penis?). Moreover, ducks' penises are very bizarre: beside a great variation a half-inch (1.2 cm) to 17 inches long, they are extremely variable in shape, from smooth to covered with spines, grooves and variably curled.
But what for?
A new research has found a huge surprise unnoticed by ornithologists till now: similar female genitalia correspond to such penises, apparently evolved to turn it difficult for males to successfully mate against the female's will. What's interesting is that most birds lack penises: just 3 % of all living bird keep one from reptilian ancestors and is seen as a primitive trait: ostriches (and related kiwi and tinamous) and waterfowl (ducks, geese, swans).But what penises have those that do have!...
Till now, it was thought that these penises were just the result of the male competition to fertilize females. But the research team discovered unexpectedly that while birds have vaginas (oviducts) like simple tubes, the vaginas of female waterfowl are just as ornate as male genitalia, with many "dead ends" (lateral sacs) and other countermeasures, seemingly designed to impede successful fertilization.
"If the phallus were to enter one of these sacs, it would not progress further into the oviduct where it would deposit sperm more effectively." said lead researcher Patricia Brennan, behavioral ecologist from both Yale University and the University of Sheffield in Britain.
Ducks' oviducts also possess some tight, clock-wise spirals.
"Interestingly, the male phallus is also a spiral, but it twists in the opposite, counterclockwise, direction," said co-researcher Richard Prum, Yale ornithologist.
"So, the twists in the oviduct appear designed to exclude the opposing twists of the male phallus, behaving like the opposite of a lock-and-key system."
The complexity of sacs and spirals in the waterfowl vagina has been found to be linked to the male penis length amongst the 14 species of ducks and geese investigated by the team, pointing to a war between the sexes in controlling mating.
"Despite the fact that most waterfowl form monogamous pairs, forced copulations by other males-the avian equivalent of rape-are common in many waterfowl," said Prum.
The "rape" frequency is strongly linked to the penis development.
"In response to male attempts to force their paternity on females, female waterfowl may be able to assert their own behavioral and anatomical means of controlling who fathers their offspring. Some large waterfowl that are highly monogamous, like geese and swans, have small phalluses, whereas other species that are quite small but more promiscuous have more elaborate genitalia," Brennan said.
"A larger phallus is advantageous in situations where there is more promiscuity, while more monogamous species have a much reduced phallus."
The researchers speculate that when a female agrees with a chosen male partner, her cooperation could help the penis bypass the complicated defenses.
"If the female is constantly struggling during unwanted copulations, this may prevent the phallus from being able to bypass the blind pouches," Brennan told LiveScience.
These amazing findings "help dispel the notion that females are simply passive members of the battle between the sexes," said evolutionary biologist Robert Montgomerie at Queen's University at Kingston in Canada, not involved in the research.
"This study, and many like it, serve to remind us that we should pay equal attention to both sexes when it comes to the process of making babies."
"Other species that exhibit forced copulation behavior, although rare, should be examined" for similar adaptations to their anatomy," added ornithologist Kevin Johnson at the Illinois Natural History Survey in Champaign.
From Wikipedia, the free encyclopedia [footnote references available in original article]
For other uses, see Mallard (disambiguation).
"Wild Duck" redirects here. For the play by Henrik Ibsen, see The Wild Duck.
|Female (left) and male (right)|
|Global range (native and introduced) Year-Round Range Summer Range Winter Range|
Anas boschas Linnaeus, 1758
The mallard (// or //) or wild duck (Anas platyrhynchos) is a dabbling duck which breeds throughout the temperateand subtropical Americas, Europe, Asia, and North Africa, and has beenintroduced to New Zealand, Australia, Peru, Brazil, Uruguay, Argentina,Chile, the Falkland Islands and South Africa. This duck belongs to thesubfamily Anatinae of the waterfowl family Anatidae.
The male birds (drakes) have a glossy green head and are grey on wings and belly, while the females (hens or ducks) have mainly brown-speckledplumage. Both sexes have an area of white-bordered black speculum feathers which commonly also include iridescent blue feathers especially among males. Mallards live in wetlands, eat water plants and small animals, and are social animals preferring to congregate in groups or flocks of varying sizes. This species is the ancestor of most breeds ofdomestic ducks.
Taxonomy and evolution
The mallard was one of the manybird species originally described byCarl Linnaeus in his 18th-century work, Systema Naturae, and still bears its original binomial name.
The name mallard is derived from the Old French malart or mallart"wild drake", although its ultimate derivation is unclear. It may be related to (or at least influenced by) an Old High German masculine proper name Madelhart, clues lying in the alternate English forms "maudelard" or "mawdelard". Masle (male) has also been proposed as an influence. Mallards frequently interbreed with their closest relatives in the genus Anas, such as the American black duck, and also with species more distantly related, such as the northern pintail, leading to varioushybrids that may be fully fertile. This is quite unusual among such different species, and apparently is because the mallard evolved very rapidly and recently, during the Late Pleistocene. The distinct lineages of this radiation are usually kept separate due to non-overlapping ranges and behavioural cues, but are still not fully genetically incompatible. Mallards and their domesticated conspecifics are also fully interfertile.
The genome of Anas platyrhynchos was sequenced in 2013.
Mallards appear to be closer to their Indo-Pacific relatives than to their American ones judging frombiogeography. Considering mitochondrial DNA D-loop sequence data, they may have evolved in the general area of Siberia; mallard bones rather abruptly appear in food remains of ancient humans and other deposits of fossilbones in Europe, without a good candidate for a local predecessor species. The large ice age palaeosubspecieswhich made up at least the European and west Asian populations during the Pleistocene has been named Anas platyrhynchos palaeoboschas.
In their mitochondrial DNA, mallards are differentiated between North America and Eurasia, however, in the nuclear genome there is a particular lack of genetic structure. Haplotypes typical of American mallard relatives and spotbills can be found in mallards around the Bering Sea. The Aleutian Islands hold a population of mallards that appear to be evolving towards a subspecies, as gene flow with other populations is very limited.
The size of the mallard varies clinally, and birds from Greenland, although larger than birds further south, have smaller bills and are stockier. They are sometimes separated as subspecies, the Greenland mallard (A. p. conboschas).
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 back (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 visually 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 3 years, but they can live to twenty.
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 colouration.
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 female has a deeper quack stereotypically associated with ducks. Male mallards also make a sound which is phonetically similar to that of the female, but it is a deep and raspy sound which can also sound like mek or whak.
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).
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Distribution and habitat
The mallard is widely distributed across the Northern and Southern Hemispheres; in North America from southern and central Alaska to Mexico, the Hawaiian Islands, across Eurasia, from Iceland and southern Greenland and parts of Morocco (North Africa) in the west, Scandinavia to the north, and to Siberia, Japan,and South Korea, in the east, Australia and New Zealand in the Southern hemisphere. It is strongly migratory in the northern parts of its breeding range, and winters farther south. For example, in North America, it winters south to Mexico, but also regularly strays into Central America and the Caribbean between September and May.
The mallard inhabits a wide range of habitat and climates, from Arctic tundra to subtropical regions. It is found in both fresh- and salt-water wetlands, including parks, small ponds, rivers, lakes and estuaries, as well as shallow inlets and open sea within sight of the coastline. Water depths of less than 1 metre (3.3 ft) are preferred, birds avoiding areas more than a few metres deep. They are attracted to bodies of water with aquatic vegetation.
The mallard is omnivorous and very flexible in its foods choice. Its diet may vary based on several factors, including the stage of the breeding cycle, short-term variations in available food, nutrient availability, and interand intraspecific competition. The majority of the mallard's diet seems to be made up of gastropods,invertebrates (including beetles, flies, lepidopterans, dragonflies, and caddisflies), crustaceans, worms, many varieties of seeds and plant matter, and roots and tubers. During the breeding season, male birds were recorded to have eaten 37.6% animal matter and 62.4% plant matter, most notably Echinochloa crus-galli, and nonlaying females ate 37.0% animal matter and 63.0% plant matter, while laying females ate 71.9% animal matter and only 28.1% plant matter. Plants generally make up a larger part of the bird's diet, especially during autumn migration and in the winter.
It usually feeds by dabbling for plant food or grazing; there are reports of it eating frogs. It usually nests on a river bank, but not always near water. It is highly gregarious outside of the breeding season and forms largeflocks, which are known as sords.
Mallards usually form pairs (in October and November in the Northern hemisphere) only until the female lays eggs at the start of nesting season which is around the beginning of spring, at which time she is left by the male who joins up with other males to await the moulting period which begins in June (in the Northern hemisphere). During the brief time before this, however, the males are still sexually potent and some of them either remain on standby to sire replacement clutches (for female Mallards that have lost or abandoned their previous clutch) or forcibly mate with females that appear to be isolated or unattached regardless of their species and whether or not they have a brood of ducklings.
The nesting period can be very stressful for the female since she lays more than half her body weight in eggs. She requires a lot of rest and a feeding/loafing area that is safe from predators. When seeking out a suitable nesting site, the female's preferences are areas that are well concealed, inaccessible to ground predators, or have few predators nearby. This can include nesting sites in urban areas such as roof gardens, enclosed courtyards, and flower boxes on window ledges and balconies more than one story up, which the ducklings cannot leave safely without human intervention. The clutch is 8–13 eggs, which are incubated for 27–28 days to hatching with 50–60 days to fledgling. The ducklings are precocial and fully capable of swimming as soon as they hatch. However,filial imprinting compels them to instinctively stay near the mother not only for warmth and protection but also to learn about and remember their habitat as well as how and where to forage for food. When ducklings mature into flight-capable juveniles, they learn about and remember their traditional migratory routes (unless they are born and raised in captivity). After this, the juveniles and the mother may either part or remain together until the breeding season arrives.
During the breeding season, both male and female mallards can become aggressive, driving off competitors to themselves or their mate by charging at them. Males tend to fight more than females, and attack each other by repeatedly pecking at their rival's chest, ripping out feathers and even skin on rare occasions.
When they pair off with mating partners, often one or several drakes end up left out. This group sometimes targets an isolated female duck, even one of a different species, and proceeds to chase and peck at her until she weakens, at which point the males take turns copulating with the female. Lebret (1961) calls this behaviour "Attempted Rape Flight" and Cramp and Simmons (1977) speak of "rape-intent flights". Male mallards also occasionally chase other male ducks of a different species, and even each other, in the same way. In one documented case of "homosexual necrophilia", a male mallard copulated with another male he was chasing after the chased male died upon flying into a glass window. This paper was awarded with an Ig Nobel Prize in 2003.
Mallards are opportunistically targeted by brood parasites, occasionally having eggs laid in their nests by Redheads, ruddy ducks, lesser scaup, gadwalls, northern shovelers, northern pintails, cinnamon teal, common goldeneyes, and other mallards. These eggs are generally accepted when they resemble the eggs of the host mallard, although the hen may attempt to eject them or even abandon the nest if parasitism occurs during egg laying. Mallards of all ages (but especially young ones) and in all locations must contend with a wide diversity of predators including raptors, mustelids, corvids, snakes, raccoons, opossums, skunks, turtles, large fish and felids and canids, including domesticated ones. The most prolific natural predators of adult mallards are red foxes (which most often pick off brooding females) and the faster or larger birds of prey, i.e. peregrine falcons,Aquila eagles or Haliaeetus eagles. In North America, adult mallards face no fewer than 15 species of birds of prey, from hen harriers and short-eared owls (both smaller than a mallard) to huge bald and golden eagles, and about a dozen species of mammalian predator, not counting several more avian and mammalian predators who threaten eggs and nestlings.
Mallards are also preyed upon by other waterside apex predators, such as the Grey heron (Ardea cinerea),European herring gull (Larus argentatus) and the Northern pike (Esox lucius). Crows (Corvus sp.) are also known to kill ducklings and adults on occasion.
Unlike many waterfowl, mallards have benefited from human alterations to the world - so much so that they are now considered an invasive species in some regions.
They are a common sight in urban parks,lakes, ponds, and other manmade water features in the regions they inhabit, and are often tolerated or encouraged among human habitat due to their placid nature towards humans and their beautiful and iridescent colors. While most are not domesticated, mallards are so successful at coexisting in human regions that the main conservation risk they pose comes from the loss of genetic diversity among a region's traditional ducks once humans and mallards colonize an area. Mallards are very adaptable, being able to live and even thrive in urban areas which may have supported more localized, sensitive species of waterfowl before development. The release of feral mallards in areas where they are not native sometimes creates problems through interbreeding with indigenous waterfowl. These non-migratory mallards interbreed with indigenous wild ducks from local populations of closely related species through genetic pollution by producing fertile offspring. Complete hybridization of various species of wild ducks gene pools could result in the extinction of many indigenous waterfowl. The wild mallard itself is the ancestor of most domestic ducks and its naturally evolved wild gene pool gets genetically polluted in turn by thedomesticated and feral populations.
Over time, a continuum of hybrids ranging between almost typical examples of either species will develop; the speciation process beginning to reverse itself. This has created conservation concerns for relatives of the mallard, such as the Hawaiian duck, the A. s. superciliosa subspecies of the Pacific black duck, the American black duck, the mottled duck, Meller's duck, theyellow-billed duck, and the Mexican duck, in the latter case even leading to a dispute whether these birds should be considered a species (and thus entitled to more conservation research and funding) or included in the mallard. In the cases mentioned below and above, however, ecological changes and hunting have led to a decline of local species; for example, the New Zealand grey duck population declined drastically due to overhunting in the mid-20th century. Hybrid offspring of Hawaiian ducks seem to be less well-adapted to native habitat, and utilizing them in reintroduction projects apparently reduces success. In summary, the problems of mallards "hybridizing away" relatives is more a consequence of local ducks declining than of mallards spreading; allopatric speciation and isolating behaviour have produced today's diversity of mallard-like ducks despite the fact that in most if not all of these populations, hybridization must have occurred to some extent. ...