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Mallard
Temporal range: Zanclean–present[a]
Female (left) and male (right) in Straßlach-Dingharting, Germany

Secure  (NatureServe)[3]
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Anseriformes
Family: Anatidae
Genus: Anas
Species:
A. platyrhynchos
Binomial name
Anas platyrhynchos
Linnaeus, 1758
Subspecies

A. p. platyrhynchos Linnaeus, 1758
A. p. conboschas C. L. Brehm, 1831

Range of A. platyrhynchos
  Breeding
  Resident
  Passage
  Non-breeding
  Vagrant (seasonality uncertain)
  Possibly extant and introduced
  Extant and introduced (seasonality uncertain)
  Possibly extant and introduced (seasonality uncertain)
Synonyms
  • Anas boschas Linnaeus, 1758
  • Anas adunca Linnaeus, 1758

The mallard (/ˈmælɑːrd, ˈmælərd/) or wild duck (Anas platyrhynchos) is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa. It has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Argentina, Chile, Colombia, the Falkland Islands, and South Africa. Belonging to the subfamily Anatinae of the waterfowl family Anatidae, mallards live in wetlands, eat water plants and small animals, and are social animals preferring to congregate in groups or flocks of varying sizes.

Males (drakes) have green heads, while the females (hens) have mainly brown-speckled plumage. Both sexes have an area of white-bordered black or iridescent purple or blue feathers called a speculum on their wings; males especially tend to have blue speculum feathers. The mallard is 50–65 cm (20–26 in) long, of which the body makes up around two-thirds the length. The wingspan is 81–98 cm (32–39 in) and the bill is 4.4 to 6.1 cm (1.7 to 2.4 in) long. It is often slightly heavier than most other dabbling ducks, weighing 0.7–1.6 kg (1.5–3.5 lb).

The female lays 8 to 13 creamy white to greenish-buff spotless eggs, on alternate days. Incubation takes 27 to 28 days and fledging takes 50 to 60 days. The ducklings are precocial and fully capable of swimming as soon as they hatch.

The non-migratory mallard interbreeds with indigenous wild ducks of closely related species through genetic pollution by producing fertile offspring. Complete hybridisation of various species of wild duck gene pools could result in the extinction of many indigenous waterfowl. This species is the main ancestor of most breeds of domestic duck, and its naturally evolved wild gene pool has been genetically polluted by the domestic and feral mallard populations.

The mallard is considered to be a species of least concern by the International Union for Conservation of Nature (IUCN), and, unlike many waterfowl, are considered an invasive species in some regions. It is a very adaptable species, being able to live and even thrive in urban areas which may have supported more localised, sensitive species of waterfowl before development.

Taxonomy and evolutionary history

[edit]

The mallard was one of the many bird species originally described in the 1758 10th edition of Systema Naturae by Carl Linnaeus.[4] He gave it two binomial names: Anas platyrhynchos and Anas boschas.[5] The latter was generally preferred until 1906 when Einar Lönnberg established that A. platyrhynchos had priority, as it appeared on an earlier page in the text.[6] The scientific name comes from Latin Anas, "duck" and Ancient Greek πλατυρυγχος, platyrhynchus, "broad-billed" (from πλατύς, platys, "broad" and ρυγχός, rhunkhos, "bill").[7] The genome of Anas platyrhynchos was sequenced in 2013.[8]

The name mallard originally referred to any wild drake, and it is sometimes still used this way.[9] It was derived from the Old French malart or mallart for "wild drake" although its true derivation is unclear.[10] It may be related to, or at least influenced by, an Old High German masculine proper name Madelhart, clues lying in the alternative English forms "maudelard" and "mawdelard".[11] Masle (male) has also been proposed as an influence.[12]

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 various hybrids that may be fully fertile.[13] The mallard has hybridised with more than 40 species in the wild, and an additional 20 species in captivity,[14] though fertile hybrids typically have two Anas parents.[15] Mallards and their domestic conspecifics are fully interfertile; many wild mallard populations in North America contain significant amounts of domestic mallard DNA.[16][17]

Genetic analysis has shown that certain mallards appear to be closer to their Indo-Pacific relatives, while others are related to their American relatives.[18] Mitochondrial DNA data for the D-loop sequence suggest that mallards may have evolved in the general area of Siberia. Mallard bones rather abruptly appear in food remains of ancient humans and other deposits of fossil bones in Europe, without a good candidate for a local predecessor species.[19] The large Ice Age palaeosubspecies that made up at least the European and West Asian populations during the Pleistocene has been named Anas platyrhynchos palaeoboschas.[20]

Mallards are differentiated in their mitochondrial DNA between North American and Eurasian populations,[21] but the nuclear genome displays a notable lack of genetic structure.[22] Haplotypes typical of American mallard relatives and eastern spot-billed ducks can be found in mallards around the Bering Sea.[23] The Aleutian Islands hold a population of mallards that appear to be evolving towards becoming a subspecies, as gene flow with other populations is very limited.[19]

Also, the paucity of morphological differences between the Old World mallards and the New World mallard demonstrates the extent to which the genome is shared among them such that birds like the eastern spot-billed duck are highly similar to the Old World mallard, and birds such as the Hawaiian duck are highly similar to the New World mallard.[24]

Subspecies

[edit]

Two subspecies are currently accepted:[25]

Image Scientific name Distribution Characteristics

Sisimiut, Greenland
A. p. conboschas
C. L. Brehm, 1831
Greenland, resident endemic. Slightly larger, but with a smaller bill (an example of Bergmann's rule); paler plumage, and stockier body.

Kłodzko, Poland
A. p. platyrhynchos
Holarctic, except for Greenland. The size of the nominate subspecies of mallard varies clinally.[26] Note that domesticated ducks, although often cited as "A. p. domesticus", do not comprise a valid distinct subspecies; they are derived from within A. p. platyrhynchos.

In the past, several other ducks, now treated as distinct species, were sometimes treated as subspecies of mallard:[27]

Description

[edit]

The mallard is a medium-sized waterfowl species that 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),[28]: 505  and weighs 0.7–1.6 kg (1.5–3.5 lb).[29] 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).[30]

Adult drake mallard

The breeding male mallard is unmistakable, with a glossy bottle-green head and a white collar that demarcates the head and neck from the purple-tinged brown breast, grey-brown wings, and a pale grey belly.[31] The rear of the male is black, with white-bordered dark tail feathers.[28]: 506  The bill of the male is a yellowish-orange tipped with black, with that of the female generally darker and ranging from black to mottled orange and brown.[32] 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.[28]: 506  Mallards, like other sexually-dimorphic birds, can sometimes go though spontaneous sex reversal,[33] often caused by damaged or nonfunctioning sex organs, such as the ovaries in mallard hens.[34] This phenomenon can cause female mallards to exhibit male plumage, and vice versa (phenotypic feminisation or masculinisation). Both male and female mallards have distinct iridescent purple-blue speculum feathers edged with white, which are prominent in flight or at rest but temporarily shed during the annual summer moult.[35] Upon hatching, the plumage 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.[36] Its legs and bill are also black.[36] As it nears a month in age, the duckling's plumage starts becoming drab, looking more like the female, though more streaked, and its legs lose their dark grey colouring.

An American black duck (upper left) and a male mallard (lower right) in eclipse plumage

[28]: 506  Two months after hatching, the fledgling period has ended, and the duckling is now a juvenile.[37] The duckling is able to fly 50–60 days after hatching. Its bill soon loses its dark grey colouring, and its sex can finally be distinguished visually by three factors: 1) the bill is yellow in males, but black and orange in females;[38] 2) the breast feathers are reddish-brown in males, but brown in females;[38] and 3) in males, the centre tail feather (drake feather) is curled, but in females, the centre tail feather is straight.[38] 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 gradually changes to its characteristic colours.[39] This change in plumage 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.[39] The adulthood age for mallards is fourteen months, and the average life expectancy is three years, but they can live to twenty.[40]

Several species of duck have brown-plumaged females that can be confused with the female mallard.[41] The female gadwall (Mareca strepera) has an orange-lined bill, white belly, black and white speculum that is seen as a white square on the wings in flight, and is a smaller bird.[28]: 506  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,[42] and the mottled duck (A. fulvigula), which is somewhat darker than the female mallard, and with slightly different bare-part colouration and no white edge on the speculum.[42]

Mallards are among the most common bird species to exhibit aberrant colouration, typically due to the influence of escaped domesticated ducks, more rarely to genetic mutations.[43] The female pictured here is leucistic; leucism in birds often results in 'cream-coloured', 'apricot'[44] or muted feathers on certain parts of the body.[45]

In captivity, domestic ducks come in wild-type plumages, white, and other colours.[46] 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.[46]

A noisy species, the female has the deep quack stereotypically associated with ducks.[28]: 507  The female will often call with a sequence of 2–10 quacks in a row, starting loud and with the volume gradually decreasing.[47] Male mallards make a sound phonetically similar to that of the female, a typical quack, but it is deeper and quieter compared to that of the female. Research conducted by Middlesex University on two English mallard populations found that the vocalisations of the mallard varies depending on their environment and have something akin to a regional accent, with urban mallards in London being much louder and more vociferous compared to rural mallards in Cornwall, serving as an adaptation to persistent levels of anthropogenic noise.[48][49]

When incubating a nest, or when offspring are present, females vocalise differently, making a call that sounds like a truncated version of the usual quack. This maternal vocalisation is highly attractive to their young. The repetition and frequency modulation of these quacks form the auditory basis for species identification in offspring, a process known as acoustic conspecific identification.[50] In addition, females hiss if the nest or offspring are threatened or interfered with. When taking off, the wings of a mallard produce a characteristic faint whistling noise.[51]

Showing speculum feathers:
male (top) and female (bottom)

The mallard is a rare example of both Allen's Rule and Bergmann's Rule in birds.[52] Bergmann's Rule, which states that polar forms tend to be larger than related ones from warmer climates, has numerous examples in birds,[53] as in case of the Greenland mallard which is larger than the mallards further south.[26] Allen's Rule says that appendages like ears tend to be smaller in polar forms to minimise heat loss, and larger in tropical and desert equivalents to facilitate heat diffusion, and that the polar taxa are stockier overall.[54] Examples of this rule in birds are rare as they lack external ears, but the bill of ducks is supplied with a few blood vessels to prevent heat loss,[55] and, as in the Greenland mallard, the bill is smaller than that of birds farther south, illustrating the rule.[26]

Due to the variability 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, Mareca strepera).[56]

Distribution and habitat

[edit]

The mallard is widely distributed across the Northern and Southern Hemispheres; in North America its range extends from southern and central Alaska to Mexico, the Hawaiian Islands,[57] across the Palearctic,[58] from Iceland[59] and southern Greenland[57] and parts of Morocco (North Africa)[59] in the west, Scandinavia[59] and Britain[59] to the north, and to Siberia,[60] Japan,[61] and South Korea.[61] Also in the east, it ranges to south-eastern and south-western Australia[62] and New Zealand[63] in the Southern hemisphere.[28]: 505 [2] It is strongly migratory in the northern parts of its breeding range, and winters farther south.[64][65] For example, in North America, it winters south to the southern United States and northern Mexico,[66][67] but also regularly strays into Central America and the Caribbean between September and May.[68] A drake later named "Trevor" attracted media attention in 2018 when it turned up on the island of Niue, an atypical location for mallards.[69][70]

The mallard inhabits a wide range of habitats and climates, from the Arctic tundra to subtropical regions.[71] 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.[72] Water depths of less than 0.9 metres (3.0 ft) are preferred, with birds avoiding areas more than a few metres deep.[73] They are attracted to bodies of water with aquatic vegetation.[28]: 507 

Behaviour

[edit]
Drake mallard performing the grunt-whistle[74]

Feeding

[edit]

The mallard is omnivorous and very flexible in its choice of food.[75] Its diet may vary based on several factors, including the stage of the breeding cycle, short-term variations in available food, nutrient availability, and interspecific and intraspecific competition.[76] The majority of the mallard's diet seems to be made up of gastropods,[77] insects (including beetles, flies, lepidopterans, dragonflies, and caddisflies),[78] crustaceans,[79] other arthropods,[80] worms,[77] feces of other birds,[81] many varieties of seeds and plant matter,[77] and roots and tubers.[79] During the breeding season, male birds were recorded to have eaten 37.6% animal matter and 62.4% plant matter, most notably the grass 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.[82] Plants generally make up the larger part of a bird's diet, especially during autumn migration and in the winter.[83][84]

The mallard usually feeds by dabbling for plant food or grazing; there are reports of it eating frogs, other amphibians, and fish, including carcasses.[85][81] However, in 2017 a flock of mallards in Romania were observed hunting fledglings of small migratory birds when they land in the water, which included a grey wagtail and a black redstart. This was the first documented occasion they had been seen attacking and consuming large vertebrates.[86] It usually nests on a river bank, but not always near water. It is highly gregarious outside of the breeding season and forms large flocks, which are known as "sordes".[87]

Breeding

[edit]

Mallards usually form pairs (in October and November in the Northern Hemisphere) until the female lays eggs at the start of the nesting season, which is around the beginning of spring.[88] At this 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).[89][90] 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)[91] 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.[91][92]

Nesting sites are typically on the ground, hidden in vegetation where the female's speckled plumage serves as effective camouflage,[93] but female mallards have also been known to nest in hollows in trees, boathouses, roof gardens and on balconies, sometimes resulting in hatched offspring having difficulty following their parent to water.[94]

Duckling
Swimming duckling
Female mallard with five ducklings

Egg clutches number 8–13 creamy white to greenish-buff eggs free of speckles.[95][96] They measure about 58 mm (2.3 in) in length and 32 mm (1.3 in) in width.[96] The eggs are laid on alternate days, and incubation begins when the clutch is almost complete.[96] Incubation takes 27–28 days and fledging takes 50–60 days.[95][97] The ducklings are precocial and fully capable of swimming as soon as they hatch.[98] 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.[99] Though adoptions are known to occur, female mallards typically do not tolerate stray ducklings near their broods, and will violently attack and drive away any unfamiliar young, sometimes going as far as to kill them.[100]

When ducklings mature into flight-capable juveniles, they learn about and remember their traditional migratory routes (unless they are born and raised in captivity). In New Zealand, where mallards are naturalised, the nesting season has been found to be longer; eggs and clutches are larger and nest survival is generally greater compared with mallards in their native range.[101]

In cases where a nest or brood fails, some mallards may mate for a second time in an attempt to raise a second clutch, typically around early-to-mid summer. In addition, mallards may occasionally breed during the autumn in cases of unseasonably warm weather; one such instance of a 'late' clutch occurred in November 2011, in which a female successfully hatched and raised a clutch of eleven ducklings at the London Wetland Centre.[102] During the breeding season, both male and female mallards can become aggressive, driving off competitors to themselves or their mate by charging at them.[103] 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. Female mallards are also known to carry out 'inciting displays', which encourage other ducks in the flock to begin fighting.[104] It is possible that this behaviour allows the female to evaluate the strength of potential partners.[105]

The drakes that end up being left out after the others have paired off with mating partners sometimes target an isolated female duck, even one of a different species, and proceed to chase and peck at her until she weakens, at which point the males take turns copulating with the female.[106] Lebret (1961) calls this behaviour "Attempted Rape Flight", and Stanley Cramp and K.E.L. Simmons (1977) speak of "rape-intent flights".[106] Male mallards also occasionally chase other male ducks of a different species, and even each other, in the same way.[106] 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.[106] This paper was awarded an Ig Nobel Prize in 2003.[107]

Mallards are opportunistically targeted by brood parasites, occasionally having eggs laid in their nests by redheads, ruddy ducks, lesser scaup, gadwalls, northern shovellers, northern pintails, cinnamon teal, common goldeneyes, and other mallards.[108] These eggs are generally accepted when they resemble the eggs of the host mallard, but the hen may attempt to eject them or even abandon the nest if parasitism occurs during egg laying.[109]

Predators and threats

[edit]
A male mute swan (Cygnus olor) driving off a female mallard.

In addition to human hunting, mallards of all ages (but especially young ones) and in all locations must contend with a wide diversity of predators including raptors and owls, mustelids, corvids, snakes, raccoons, opossums, skunks, turtles, large fish, felids, and canids, the last two including domestic cats and dogs.[110] The most prolific natural predators of adult mallards are red foxes (Vulpes vulpes; which most often pick off brooding females) and the faster or larger birds of prey, (e.g. peregrine falcons, Aquila or Haliaeetus eagles).[111] In North America, adult mallards face no fewer than 15 species of birds of prey, from northern harriers (Circus hudsonius) and short-eared owls (Asio flammeus) (both smaller than a mallard) to huge bald (Haliaeetus leucocephalus) and golden eagles (Aquila chrysaetos), and about a dozen species of mammalian predators, not counting several more avian and mammalian predators who threaten eggs and nestlings.[109]

Mallards are also preyed upon by other waterside apex predators, such as grey herons (Ardea cinerea),[112] great blue herons (Ardea herodias) and black-crowned night herons (Nycticorax nycticorax), the European herring gull (Larus argentatus), the wels catfish (Silurus glanis), and the northern pike (Esox lucius).[113] Crows (Corvus spp.) are also known to kill ducklings and adults on occasion.[114] Also, mallards may be attacked by larger anseriformes such as swans (Cygnus spp.) and geese during the breeding season, and are frequently driven off by these birds over territorial disputes. Mute swans (Cygnus olor) have been known to attack or even kill mallards if they feel that the ducks pose a threat to their offspring.[115] Common loons (Gavia inmer) are similarly territorial and aggressive towards other birds in such disputes, and will frequently drive mallards away from their territory.[116] However, in 2019, a pair of common loons in Wisconsin were observed raising a mallard duckling for several weeks, having seemingly adopted the bird after it had been abandoned by its parents.[117]

In summer, a combination of hot temperatures and reduced water levels place mallards at an increased risk of contracting botulism, as these conditions are ideal for Clostridium botulinum to propagate, with the birds also more likely to come into contact with botulinum toxin produced by the bacteria. Outbreaks of botulism among mallard populations can lead to mass die-offs.[118]

The predation-avoidance behaviour of sleeping with one eye open, allowing one brain hemisphere to remain aware while the other half sleeps, was first demonstrated in mallards, although it is believed to be widespread among birds in general.[119]

Status and conservation

[edit]
Several drakes swimming in a pond
A mallard (male) eats rolled oats from the hand.

Since 1998, the mallard has been rated as a species of least concern on the IUCN Red List of Endangered Species. This is because it has a large range–more than 20,000,000 km2 (7,700,000 sq mi)[120] and because its population is increasing. Also, the population size of the mallard is very large.[2]

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.[121] They are a common sight in urban parks, lakes, ponds, and other human-made water features in the regions they inhabit, and are often tolerated or encouraged in human habitat due to their placid nature towards humans, their ducklings and their beautiful and iridescent colours.[35] 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 colonise an area. Mallards are very adaptable, being able to live and even thrive in urban areas which may have supported more localised, sensitive species of waterfowl before development.[122] The release of feral mallards in areas where they are not native sometimes creates problems through interbreeding with indigenous waterfowl.[121][123] These non-migratory mallards interbreed with indigenous wild ducks from local populations of closely related species through genetic pollution by producing fertile offspring.[123] Complete hybridisation of various species of wild duck gene pools could result in the extinction of many indigenous waterfowl.[123] The mallard itself is the ancestor of most domestic ducks, and its naturally evolved wild gene pool gets genetically polluted in turn by the domestic and feral populations.[124]

Over time, a continuum of hybrids ranging between almost typical examples of either species develop; the speciation process is beginning to reverse itself.[125] This has created conservation concerns for relatives of the mallard, such as the Hawaiian duck,[126][127] the New Zealand grey duck (A. s. superciliosa) subspecies of the Pacific black duck,[126][128] the American black duck,[129][130] the mottled duck,[131] Meller's duck,[132] the yellow-billed duck,[125] and the Mexican duck,[126][131] in the latter case even leading to a dispute as to whether these birds should be considered a species[133] (and thus entitled to more conservation research and funding) or included in the mallard species. Ecological changes and hunting have also 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.[128] Hybrid offspring of Hawaiian ducks seem to be less well adapted to native habitat, and using them in re-introduction projects apparently reduces success.[126][134] In summary, the problems of mallards "hybridising 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, hybridisation must have occurred to some extent.[135]

Invasiveness

[edit]
The last male Mariana mallard

Mallards are causing severe "genetic pollution" to South Africa's biodiversity by breeding with endemic ducks[136] even though the Agreement on the Conservation of African-Eurasian Migratory Waterbirdsan agreement to protect the local waterfowl populations – applies to the mallard as well as other ducks.[137] The hybrids of mallards and the yellow-billed duck are fertile, capable of producing hybrid offspring.[138] If this continues, only hybrids occur and in the long term result in the extinction of various indigenous waterfowl.[138] The mallard can crossbreed with 63 other species, posing a severe threat to indigenous waterfowl's genetic integrity.[139] Mallards and their hybrids compete with indigenous birds for resources, including nest sites, roosting sites, and food.[136]

Availability of mallards, mallard ducklings, and fertilised mallard eggs for public sale and private ownership, either as poultry or as pets, is currently legal in the United States, except for the state of Florida, which has currently banned domestic ownership of mallards. This is to prevent hybridisation with the native mottled duck.[140]

The mallard is considered an invasive species in Australia and New Zealand,[28]: 505  where it competes with the Pacific black duck (known as the grey duck locally in New Zealand) which was over-hunted in the past. There, and elsewhere, mallards are spreading with increasing urbanisation and hybridising with local relatives.[126]

The eastern or Chinese spot-billed duck is currently introgressing into the mallard populations of the Primorsky Krai, possibly due to habitat changes from global warming.[23] The Mariana mallard was a resident allopatric population – in most respects a good species – apparently initially derived from mallard-Pacific black duck hybrids;[141] it became extinct in the late 20th century.[142]

The Laysan duck is an insular relative of the mallard, with a very small and fluctuating population.[143][2] Mallards sometimes arrive on its island home during migration, and can be expected to occasionally have remained and hybridised with Laysan ducks as long as these species have existed.[144] However, these hybrids are less well adapted to the peculiar ecological conditions of Laysan Island than the local ducks, and thus have lower fitness. Laysan ducks were found throughout the Hawaiian archipelago before 400 AD, after which they suffered a rapid decline during the Polynesian colonisation.[145] Now, their range includes only Laysan Island.[145] It is one of the successfully translocated birds, after having become nearly extinct in the early 20th century.[146]

Relationship with humans

[edit]

Domestication

[edit]
An American Pekin duck, a breed of domestic duck derived from the mallard

Mallards have often been ubiquitous in their regions among the ponds, rivers, and streams of human parks, farms, and other human-made waterways – even to the point of visiting water features in human courtyards.[147]

Mallards have had a long relationship with humans. Almost all domestic duck breeds derive from the mallard, with the exception of a few Muscovy breeds,[148] and are listed under the trinomial name A. p. domesticus. Mallards are generally monogamous while domestic ducks are mostly polygamous. Domestic ducks have no territorial behaviour and are less aggressive than mallards.[149] Domestic ducks are mostly kept for meat; their eggs are also eaten, and have a strong flavour.[149] They were first domesticated in Southeast Asia at least 4,000 years ago, during the Neolithic Age, and were also farmed by the Romans in Europe, and the Malays in Asia.[150] As the domestic duck and the mallard are the same species as each other, it is common for mallards to mate with domestic ducks and produce hybrid offspring that are fully fertile.[151] Because of this, mallards have been found to contain genes of the domestic duck.[151]

While the keeping of domestic breeds is more popular, pure-bred mallards are sometimes kept for eggs and meat,[152] although they may require wing clipping to restrict flying.

Hunting

[edit]
George Hetzel, mallard still life painting, 1883–1884

Mallards are one of the most common species shot in waterfowl hunting due to their large population size. The ideal location for hunting mallards is considered to be where the water level is somewhat shallow where the birds can be found foraging for food.[153] Hunting mallards might cause the population to decline in some places, at some times, and with some populations.[154] In certain countries, the mallard may be legally shot but is protected under national acts and policies. For example, in the United Kingdom, the mallard is protected under the Wildlife and Countryside Act 1981, which restricts certain hunting methods or taking or killing mallards.[155]

Mallard-vehicle collisions

[edit]

Since standardized data collection began in 1990, the United States Federal Aviation Administration has recorded 1320 mallard collisions with aircraft, 261 of which caused damage to the craft (through 2022).[156] In the United States, the mallard ranks as the 7th most hazardous bird to both military and commercial aircraft.[157][158] Mallards are of particular concern due to their ubiquity; they are widespread and adaptable to urban environments.[159][160] Mallards also generally fail to avoid approaching vehicles in experimental settings, especially at high vehicle speeds.[160]

Though most bird strikes occur during the takeoff and landing phases of flight,[156] at least one mallard has been struck at cruising altitude (21,000 feet).[161]

As food

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Since ancient times, the mallard has been eaten as food. The wild mallard was eaten in Neolithic Greece.[162] Usually, only the breast and thigh meat is eaten.[163] It does not need to be hung before preparation, and is often braised or roasted, sometimes flavoured with bitter orange or with port.[164]

In culture

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Make Way for Ducklings is a children's picture book written and illustrated by Robert McCloskey. The book centers on a pair of mallards who raise their ducklings in the Boston Public Garden.[165]

Migration is an animated adventure comedy film produced by Universal Pictures and Illumination. The story follows a family of mallards who try to migrate from New England to Jamaica.[166]

The world's loneliest duck, named "Trevor" by locals after New Zealand politician Trevor Mallard, appeared without explanation on the Pacific island of Niue, dying there in 2019.

Footnotes

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References

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from Grokipedia
The mallard (Anas platyrhynchos) is a medium to large dabbling duck species, recognized as the most abundant and widespread waterfowl across the Northern Hemisphere. Native to temperate and subtropical wetlands of Eurasia, North America, and North Africa, it inhabits diverse aquatic environments including ponds, marshes, rivers, and estuaries, often adapting to urban and agricultural areas. Males exhibit distinctive plumage with an iridescent green head, white neck ring, chestnut breast, and curled black tail feathers, while females and juveniles display mottled brown patterns for camouflage. As opportunistic feeders, mallards primarily dabble for aquatic vegetation, seeds, insects, and small vertebrates, contributing to wetland ecosystems through seed dispersal and nutrient cycling. The species serves as the primary ancestor of domestic duck breeds and has established introduced populations globally, though widespread hybridization with feral domestic strains and other wild ducks raises concerns for genetic integrity in certain native taxa. Classified as Least Concern by the IUCN, its global population exceeds 25 million individuals and remains stable or increasing in many regions despite hunting pressures.

Taxonomy

Evolutionary origins

The mallard (Anas platyrhynchos) belongs to the genus Anas within the Anatidae family, a clade of waterfowl that originated in the Paleogene period, with early fossils of potential precursors like Romainvilliidae dating to the late Eocene in Eurasia. The genus Anas, encompassing dabbling ducks, underwent adaptive radiation during the Pliocene and Pleistocene, driven by ecological opportunities in temperate wetlands and facilitated by traits such as versatile filter-feeding via broad lamellate bills, which trace back to ancestral Anatidae morphologies adapted for sifting invertebrates and vegetation from shallow waters. The earliest fossils morphologically similar to the mallard appear in late Pliocene deposits, approximately 5 million years ago, indicating the species' lineage had coalesced by this time amid cooling climates that expanded suitable habitats. Phylogenetic analyses place the mallard's divergence from closely related Anas species, such as the American black duck (A. rubripes), at around 600,000 years before present, within the Pleistocene epoch, a period marked by glacial cycles that promoted isolation and subsequent reconnection across the Holarctic realm. This timing aligns with fossil evidence of mallard-like dabbling ducks in Eurasian Pleistocene strata, supporting an origin centered in Eurasia before bidirectional dispersal into North America via Beringian land bridges. Genetic studies using nuclear loci and whole-genome data confirm the mallard's position as a basal or central taxon in the Anas (mallard) complex, with shared polymorphisms across species reflecting ancient gene flow rather than recent convergence. These evolutionary dynamics underscore the mallard's success through opportunistic traits, including high dispersal capability via strong flight and a broad diet, which enabled colonization of diverse Holarctic environments without eroding species boundaries despite hybridization. Sustained genomic exchange with congeners, as evidenced by shared SNPs in mitochondrial and nuclear markers, likely enhanced adaptive resilience to fluctuating climates, though the fossil record remains sparse pre-Pleistocene, limiting precise reconstruction of early radiations.

Subspecies and genetic variation

The Mallard (Anas platyrhynchos) is recognized as comprising a small number of subspecies, primarily distinguished by subtle morphological traits such as body size, bill shape, and plumage coloration intensity, alongside geographic isolation. The nominate subspecies A. p. platyrhynchos inhabits much of the Palearctic and Nearctic regions, exhibiting the typical pronounced sexual dimorphism with males displaying iridescent green heads and females mottled brown plumage. In contrast, A. p. diazi, the Mexican duck, occurs in the southwestern United States and Mexico, with individuals generally larger and showing reduced sexual dimorphism, including darker, less glossy male plumage and females with warmer tones. Other proposed subspecies, such as A. p. conboschas in Greenland, are debated due to limited morphological divergence and potential gene flow, often lacking formal recognition in modern taxonomic assessments. Genetic analyses underscore modest differentiation among these subspecies, with mitochondrial and nuclear markers revealing low but detectable divergence times linked to Pleistocene isolation events. For instance, phylogeographic studies indicate that eastern and western populations diverged during late Pleistocene glacial periods, when populations were confined to refugia, fostering localized adaptations in size and migratory behavior through drift and selection. Recent genome-wide sequencing, including assemblies from 2025 studies on multiple Anas species, has identified millions of single nucleotide polymorphisms (SNPs) and insertions/deletions (indels) within A. platyrhynchos, reflecting high heterozygosity (e.g., up to 1.57 million indels per comparison) that supports population resilience amid environmental pressures. These metrics highlight the species' adaptability, with autosome-wide variation exceeding Z-chromosome differentiation in some regional comparisons, suggesting historical gene flow has blurred stricter boundaries. Overall, subspecies boundaries remain fluid under genetic scrutiny, as morphological traits correlate weakly with genomic clusters, emphasizing A. platyrhynchos' capacity for rapid dispersal and local adaptation over rigid taxonomic divisions.

Hybridization dynamics

Mallards exhibit high rates of hybridization with closely related duck species in areas of sympatry, facilitated by secondary contact and behavioral similarities in mating. Genetic analyses using thousands of ddRAD-seq loci have quantified introgression levels, revealing up to 25% hybridization rates between mallards and American black ducks (Anas rubripes) in eastern North American contact zones. These studies, spanning 2019 to 2021, demonstrate ongoing gene flow through backcrossing, with mallard alleles introgressing into black duck populations at rates that erode genetic distinctiveness over time. Hybridization dynamics with the Hawaiian duck (A. wyvilliana) trace to ancient events, where genomic evidence supports an origin via mallard introgression, followed by persistent modern gene flow from feral mallards introduced in the 20th century. Coalescent models indicate nonzero gene flow from mallards into Hawaiian duck ancestors, contributing to multiple hybrid swarms across Hawaiian Islands as of 2019 assessments. In New Zealand, anthropogenic releases of domestic mallards since the 19th century have amplified hybridization with native gray ducks (A. superciliosa), with 2025 genomic analyses showing domestic mallard alleles swamping native genotypes, reducing gray duck fitness and aiding mallard naturalization. Empirical data highlight gene swamping risks, as in eastern North America where mallard competition and hybrid superiority in mate attraction contribute to black duck displacement, potentially leading to local extinctions without full genomic assimilation. Conversely, introgression can confer adaptive benefits, such as increased resilience to environmental changes in hybrid mallard populations compared to pure natives, as evidenced by higher genomic vulnerability in New Zealand gray ducks. This duality frames hybridization as a natural evolutionary mechanism—evident in ancient divergences around 600,000 years ago between mallards and black ducks—yet accelerated by human-mediated introductions, balancing potential for enhanced adaptability against losses in lineage-specific biodiversity.

Physical description

Plumage and dimorphism

Adult male mallards, or drakes, display striking sexual dimorphism in their breeding plumage, characterized by an iridescent green head, a narrow white neck ring, a chestnut-colored breast, gray flanks, and a black rear with curled tail feathers. This vibrant coloration contrasts sharply with the mottled brown plumage of females, which features buff tones with dark streaks and spots for effective crypsis on nests and in surrounding vegetation. Both sexes possess a distinctive speculum—a blue iridescent patch on the secondary wing feathers bordered by white—serving as a key identifier during flight and across plumage variations. Following the breeding season, typically from late summer to early fall, male mallards undergo an eclipse molt, transitioning to a drab, female-like plumage that reduces visibility and predation risk while they are flightless during remige replacement. This seasonal ecdysis is regulated by declining testosterone levels post-breeding, which trigger the shift from bright nuptial feathers to cryptic ones, with drakes regaining breeding plumage via a pre-basic molt influenced by rising androgen concentrations. Females maintain relatively stable plumage year-round, with minor wear but no equivalent dramatic molt, prioritizing consistent camouflage over display. The pronounced dimorphism functions primarily in mate selection, where male brightness signals genetic quality and health to females, as evidenced by preference studies favoring intact green heads and brown chests. However, this conspicuousness incurs higher predation vulnerability for males during breeding, balancing sexual selection pressures against survival costs, while female drabness enhances nest concealment and evasion from predators. Empirical field observations confirm that such trade-offs underpin the evolution of dichromatic plumages in Anatidae, with the speculum providing species-specific recognition amid hybridization risks.

Size, weight, and measurements

Adult mallards exhibit moderate sexual size dimorphism, with males generally larger and heavier than females. Total body length averages 50–65 cm, with males measuring 55–65 cm and females 50–60 cm; wingspan ranges from 81–98 cm across both sexes. Body weight typically falls between 1.0 and 1.6 kg, though males average 1.2–1.4 kg and females 1.0–1.3 kg, reflecting males being approximately 10–21% heavier.
MeasurementMalesFemalesBoth Sexes
Length (cm)55–6550–6050–65
Weight (kg)1.2–1.41.0–1.31.0–1.6
Wingspan (cm)81–9881–9881–98
Ducklings grow rapidly, attaining near-adult body size within 8–10 weeks after hatching, coinciding with fledging at 7–8 weeks when wing feathers fully develop for flight. During this period, accumulation of fat reserves becomes critical, providing energy for post-fledging dispersal and supporting endurance during early migrations, where juveniles may lose up to 50% of body mass over long flights.

Distribution and habitat preferences

Native range

The mallard (Anas platyrhynchos) is native to the Holarctic realm, with its indigenous distribution spanning temperate and subarctic regions across North America and Eurasia. Breeding populations historically occupied areas from Alaska and the Mackenzie Delta southward through central and western North America to southern California and northern Mexico, as well as across Europe to Siberia and temperate Asia. Wintering ranges extend into subtropical latitudes, including northern Mexico, the Mediterranean region of North Africa, and southern parts of Asia as far as northern India. Pre-1900 historical records, derived from ornithological surveys and fossil evidence, delineate the core native extent without established populations in the Southern Hemisphere, including Australasia and Antarctica, where the species was absent until deliberate introductions beginning in the mid-19th century. In Eurasia, archaeological findings from Pleistocene deposits confirm long-term presence in temperate wetlands, while North American records prior to European settlement limit breeding to prairie and boreal zones rather than eastern coastal areas. The species exhibits strong affinities for shallow freshwater habitats such as pothole wetlands, slow-moving rivers, and lake margins, which support nesting and foraging during breeding seasons. Mid-20th-century aerial surveys and ground-based density mappings in North America highlight concentrations in the prairie pothole ecoregion of the northern Great Plains, where wetland abundance correlates with elevated breeding pair densities exceeding 100 pairs per square kilometer in optimal years. Long-term monitoring data indicate relative stability in core Holarctic breeding grounds, though satellite telemetry and banding recoveries from the late 20th and early 21st centuries document gradual poleward expansions in northern latitudes, potentially linked to warming trends, without contraction in established temperate zones.

Introduced populations

The mallard (Anas platyrhynchos) was introduced to New Zealand in the 1860s, beginning with a pair imported to the South Island by the Otago Acclimatisation Society from Melbourne, Australia, as part of broader efforts to establish game birds for hunting. Subsequent releases from multiple sources, including domestic stock, facilitated rapid establishment, with populations becoming self-sustaining through escapes and intentional liberations across both islands by the late 19th century. In Australia, introductions commenced as early as 1862 via acclimatization societies aiming to stock waterways for sport, leading to feral populations that underwent significant range expansion, particularly from the 1950s onward in temperate wetlands and agricultural areas. Similarly, mallards were introduced to Hawaii in the early 20th century for ornamental and hunting purposes, establishing feral groups primarily through aviary escapes and releases, which have persisted in lowland wetlands and urban ponds. These patterns reflect human-mediated dispersal from Eurasian and North American stock, often involving game-farm strains. Genetic analyses of introduced populations indicate minimal founder effects or bottlenecks, attributable to repeated introductions from diverse sources that promoted admixture and maintained genetic diversity comparable to managed North American game-farm lineages. This admixture has supported adaptive colonization, evidenced by swift occupation of urban and agrarian habitats; for instance, feral groups in South American countries like Argentina and Brazil have filled suitable niches post-20th-century releases, demonstrating ecological fitting to anthropogenic landscapes without severe demographic constraints.

Behavioral ecology

Foraging strategies

Mallards are dabbling ducks that forage primarily by tipping their bodies forward in shallow water, submerging their heads and necks while elevating their tails, to sieve food from sediment and aquatic substrates using broad bills lined with comb-like lamellae that filter particles. Their omnivorous diet consists mainly of plant matter, including seeds from wetland plants such as smartweed (Polygonum spp.) and barnyard grass (Echinochloa spp.), aquatic vegetation, acorns, and agricultural grains like corn and rice, which often dominate intake based on availability. Invertebrates, such as aquatic worms (Naididae) and snails (Planorbidae, Physidae), supplement the diet and are selected disproportionately relative to their abundance in habitats. Gut content analyses from spring-collected females indicate plant material comprises approximately 65% of dry biomass, with seeds forming the bulk, while animal matter accounts for 35%, reflecting selection for nutrient-rich invertebrates in productive wetlands. Seasonal shifts occur, with higher proportions of animal prey, primarily invertebrates, consumed during spring and summer to support breeding demands, transitioning to plant-dominated diets in autumn and winter as seeds and crops become prevalent. Mallards display opportunistic foraging, exploiting human-altered environments by scavenging urban waste like bread and accessing agricultural fields, where cereal crops sustain elevated densities during non-breeding periods. Stable isotope analyses confirm their mid-trophic omnivorous position, with broader niches in urban habitats indicating dietary flexibility and incorporation of anthropogenic resources.

Breeding biology

Mallards form seasonally monogamous pairs, with females primarily driving mate choice through selection based on male courtship displays such as head-shaking and wing-flapping. However, males frequently engage in forced copulations, accounting for up to 40% of mating attempts in observations, though genetic paternity analyses indicate that most offspring are sired by the social mate due to female anatomical adaptations that favor preferred partners. This reflects evolutionary pressures balancing female choice against male coercion in waterfowl reproductive strategies. Females construct nests in shallow ground depressions lined with vegetation and breast down, typically within 100 meters of water bodies for proximity to foraging and escape routes. Clutches consist of 8-13 eggs, laid at intervals of 1-2 days, with incubation performed solely by the female lasting approximately 28 days. Upon hatching, precocial ducklings leave the nest within 12-24 hours, following the female to water while she provides protection and leads foraging efforts. Ducklings remain dependent on the female for brooding and guidance until fledging at 50-60 days, when they achieve flight capability. Annual reproductive productivity, derived from survival models incorporating clutch size, nest success (often 30-50%), and duckling survival rates (typically 40-60%), averages 4-6 fledglings per breeding pair in temperate populations, though this varies with habitat quality and predation pressure. Banding and demographic studies confirm that low duckling survival often limits recruitment more than nesting success.

Migration and social patterns

Mallards (Anas platyrhynchos) are partial migrants, with northern populations in Canada and Alaska typically undertaking short- to medium-distance southward journeys of 1,000–3,000 km to wintering areas in the southern United States and northern Mexico, while southern and temperate populations remain largely sedentary year-round. These movements follow distinct flyways and involve facultative responses to environmental cues, including irruptive southward shifts during extreme cold snaps that exceed local foraging thresholds. Staging occurs at protected refuges along migration corridors, where birds accumulate fat reserves before continuing, as documented in banding and telemetry data from eastern and midcontinent stocks. Post-breeding, mallards aggregate into large rafts of hundreds to over 1,000 individuals on open water, enhancing safety through predator dilution and improved detection via collective scanning behaviors. These flocks exhibit stable linear dominance hierarchies, particularly among males, where higher-ranked individuals secure priority access to resources via ritualized aggression such as head-pumping and chasing, with empirical rates of 0.5–2.0 aggressive acts per hour observed in wintering groups. Hierarchy stability persists across seasons, influenced by body size and prior residency, though subordinates experience elevated stress responses measurable via corticosterone levels. Breeding site philopatry is pronounced in females, with return rates to previous nest sites or natal wetlands averaging 50–72% across studies, driven by familiarity with local habitat quality and reduced dispersal risks. Recent GPS telemetry from 2018–2023 reveals increasing sedentism in urban-adjacent populations, where anthropogenic food subsidies diminish migratory incentives, leading to year-round residency rates exceeding 60% in some metropolitan refugia compared to rural counterparts.

Ecological interactions

Predators and prey dynamics

Predators primarily target mallard eggs and ducklings, with avian species such as raptors, corvids, and gulls, as well as mammals including foxes and raccoons, and reptiles like bullsnakes accounting for the majority of losses. Field studies indicate predation causes substantial mortality, including 10% of nests losing eggs in the days before hatching and 15% losing ducklings prior to departure, while 30-day duckling survival rates average 35% in untreated areas, implying 65% losses largely attributable to predators. Adult mallards face lower predation pressure, evading threats through rapid flight at speeds up to 55 mph, which positions them as the fastest-flying duck species. Mallards counter predators with behaviors such as alarm calls, heightened vigilance to predatory vocalizations, and group responses that reduce detection risk for broods. Females' cryptic plumage provides camouflage during nesting, an adaptation minimizing visual detection in an evolutionary arms race with sight-based predators, whereas males' brighter nuptial feathers correlate with elevated vigilance to offset increased conspicuousness. In trophic interactions, mallards function as predators on small fauna, including aquatic invertebrates, insects, fish, and amphibians, with diet studies in wetlands showing substantial consumption that influences prey population dynamics.

Parasites, diseases, and zoonotic roles

Mallards (Anas platyrhynchos) commonly harbor helminth parasites, including trematodes such as Echinostoma trivolvis and Notocotylus attenuatus, and nematodes like Amidostomum anseris, which infect the gastrointestinal tract and gizzard. Experimental infections demonstrate that up to 50% of young mallards can develop patent infections with E. trivolvis metacercariae, while field surveys in Europe report overall helminth prevalence of 20-50% in necropsied adults, with nematodes and trematodes comprising the majority of species diversity (up to 13 nematode and 7 trematode taxa in Austrian samples). Ectoparasites, particularly lice of the Philopteridae family, exhibit near-100% prevalence in some populations, though intensities vary by habitat density. Pathogens including highly pathogenic avian influenza (HPAI) H5N1 and duck viral enteritis (duck plague, caused by anatid herpesvirus 1) frequently affect mallard populations, with the former often resulting in asymptomatic carriage that facilitates viral dissemination via migration. Mallards have been central to H5N1 outbreaks since the early 2000s, acting as reservoirs without overt clinical signs in many cases, as evidenced by widespread detections in wild birds during the 2021-2024 panzootic, including urban flocks in Europe and North America. Duck plague induces acute mortality in free-ranging mallards, manifesting as lethargy, bloody diarrhea, and reluctance to fly, with outbreaks linked to high waterfowl densities; immunosuppressed adults show heightened susceptibility, underscoring density-dependent transmission dynamics. Zoonotic transmission from mallards to humans remains empirically rare, despite their role as bacterial (Escherichia coli, Salmonella spp.) and viral carriers in proximity to human environments; for H5N1, no sustained human-to-human or direct wild bird-to-human spillovers have been documented, even amid 2024 surveillance events revealing high avian prevalence. This low-risk profile holds for other mallard-associated pathogens like avian paramyxoviruses, justifying targeted monitoring over alarmism, as proximity alone does not equate to efficient cross-species jumps absent specific adaptation evidence.

Conservation and population dynamics

The mallard (Anas platyrhynchos) is classified as Least Concern by the IUCN Red List, with the most recent assessment in 2016 confirming a large global population and extensive range despite some regional fluctuations. Global estimates place the population at approximately 19 million mature individuals, reflecting its adaptability across native and introduced ranges in the Americas, Eurasia, and beyond. In North America, breeding populations in the traditional survey area totaled 6.6 million in the 2025 U.S. Fish and Wildlife Service Waterfowl Breeding Population and Habitat Survey, marking a 1% decline from 2024 and 17% below the long-term average (1955–2024). Overall North American breeding estimates hover around 10 million, with the species demonstrating resilience amid variable habitat conditions, as noted in Ducks Unlimited analyses emphasizing stability despite periodic survey dips. Regional trends vary: eastern North American populations have declined approximately 20% since 1998 according to Partners in Flight data integrated by Audubon, with the 2024 eastern survey area estimate at 1.169 million, down 4% from 2023. In contrast, long-term European indices, such as those from the British Trust for Ornithology, indicate overall increases from 1967 levels (e.g., UK breeding populations up over 100% through the early 2000s before recent softening), though short-term data show a 34% decline over the past 25 years in some wintering indices. These patterns underscore the mallard's capacity for demographic recovery in human-modified landscapes, countering narratives of uniform vulnerability.

Identified threats

Habitat alteration through wetland drainage for agricultural expansion represents a primary empirical threat to mallard breeding success, particularly in the Prairie Pothole Region of North America, where 50-90% of pothole wetlands have been lost or degraded since European settlement around 1900, reducing available nesting and brood-rearing sites essential for high recruitment rates. This causal chain—drainage converting ephemeral wetlands to cropland—limits food resources and cover, correlating with localized population declines during periods of intensified conversion, though mallard adaptability to alternative habitats mitigates broader impacts. Extreme climatic events, including droughts and late-winter cold snaps, elevate mortality risks across life stages; for instance, cold, wet conditions during brooding increase duckling hypothermia and starvation, while droughts in breeding grounds reduce wetland availability and survival rates, with studies documenting profound fitness effects from such variability. Empirical data from radiomarked broods indicate drought years can halve duckling survival through diminished wetland persistence, amplifying recruitment bottlenecks in already fragmented landscapes. Historical lead poisoning from ingested shotgun pellets caused significant waterfowl mortality prior to regulatory bans, with pre-1991 U.S. data showing elevated crippling and death rates, but non-toxic ammunition mandates have substantially reduced exposure and poisoning incidence in hunted populations. Residual risks persist from environmental lead sources like fishing tackle, though mitigation has lowered overall population-level impacts to negligible in regulated areas. Hybridization with domestic or game-farm mallard strains introduces genetic dilution in wild populations, potentially impairing adaptive traits like migration timing and disease resistance, as evidenced by studies showing farm-released birds interbreeding and spreading maladaptive alleles, though the extent remains debated with limited evidence of widespread fitness erosion in core native ranges. In eastern North America, mallard-black duck hybridization dynamics highlight competitive displacement risks, but for mallards themselves, introgression primarily stems from anthropogenic releases rather than natural processes, with data indicating stable or increasing wild populations despite these pressures. Overall, mallard resilience—via broad dietary flexibility and urban adaptation—confers minimal existential threat globally, with declines confined to habitat-specific locales rather than systemic collapse.

Invasiveness and ecological impacts

The mallard (Anas platyrhynchos) has been introduced to numerous regions outside its native Holarctic range, establishing feral populations that exhibit invasive traits in isolated ecosystems such as oceanic islands, where they pose risks primarily through interspecific hybridization rather than wholesale habitat destruction. In Hawaii, introduced mallards hybridize extensively with the endemic koloa maoli (Anas wyvilliana), leading to genetic swamping that threatens the native species with effective extinction despite ongoing management efforts; genetic analyses indicate that pure koloa maoli now comprise less than 10% of duck populations in some wetlands, with hybrids dominating sites like Kanahā and Keālia ponds. Similarly, in New Zealand, mallards introduced in the 19th century have hybridized with the native grey duck (Anas superciliosa superciliosa), resulting in mallard-dominant populations where over 80% of observed ducks exhibit mallard or hybrid phenotypes, contributing to the displacement of pure grey ducks through both genetic introgression and competitive exclusion. Evidence for direct resource competition remains mixed, with high mallard densities correlating with reduced native duck abundance in shared wetlands, but causation unclear due to confounding factors like habitat modification; observational data suggest displacement via numerical dominance rather than superior foraging efficiency. On the positive side, introduced mallards provide ecosystem services through endozoochory, dispersing viable seeds of wetland plants over distances up to 19 km in as little as 48 hours, thereby enhancing connectivity and regeneration in fragmented habitats—a role amplified in human-altered landscapes. Regarding disease dynamics, mallards serve as natural reservoirs for highly pathogenic avian influenza viruses (HPAIV), shedding them into water bodies where transmission occurs environmentally; in dense introduced populations, this may amplify spillover risks to poultry and other wildlife compared to sparse native flocks, though experimental evidence indicates mallards often remain asymptomatic carriers without elevated virulence. Local control measures, such as targeted trapping and culling in sensitive island habitats, have proven effective at reducing mallard numbers and hybridization rates—for instance, programs on Lord Howe Island have curtailed feral mallard expansion through systematic removal—yet broader eradication remains impractical on continental scales, reflecting the species' adaptability and the absence of continent-wide ecological collapse despite introductions. Overall, while hybridization drives localized native declines, mallards do not induce the pervasive havoc seen in some invasives, given their ecological similarity to native congeners elsewhere.

Management practices including hunting

Management of mallard populations in North America primarily occurs through adaptive harvest management (AHM) frameworks administered by the U.S. Fish and Wildlife Service (USFWS), which integrate annual aerial surveys, banding data, and hunter harvest reports to set hunting regulations that account for population status, habitat conditions, and harvest levels. This process aims to maintain sustainable populations by adjusting season lengths, bag limits, and possession limits annually, with models demonstrating that harvest mortality is largely compensatory rather than additive, meaning it replaces natural mortality without depressing overall numbers. Banding programs, such as those deploying nearly 10,000 mallard bands annually in the Atlantic Flyway alone, provide recovery data essential for refining these models and estimating survival rates, enabling flyway-specific adaptive strategies. Hunting regulations include daily bag limits that vary by flyway and zone but typically allow 6 ducks total, with mallard sub-limits of 4 birds (no more than 2 hens) in many areas to protect breeding stock, alongside federal duck stamps that fund habitat conservation. Annual harvest estimates from USFWS surveys indicate around 3-4 million mallards taken across North America, yet post-hunt population indices remain stable, with no evidence of harvest-induced declines when paired with habitat monitoring. These regulated harvests function as an ecological tool for population control, mitigating risks of overabundance such as increased disease transmission in dense flocks, as supported by demographic models showing balanced mortality dynamics. Habitat interventions complement hunting by focusing on restoration through organizations like Ducks Unlimited, which have conserved millions of acres of wetlands critical for mallard nesting and foraging, including projects targeting flooded timber and grassland cover to enhance breeding success. Such efforts, often funded partly by hunting license revenues, underscore a causal link between harvest-generated income and proactive management, with economic analyses estimating waterfowl hunting expenditures exceeding $900 million annually in direct contributions to local economies via gear, travel, and services. Claims for stricter restrictions lack substantiation from long-term trend data, as AHM evaluations consistently affirm harvest sustainability without population depression.

Human relationships

Domestication history

The domestication of ducks derived from the wild mallard (Anas platyrhynchos) began approximately 2,000 years ago in southern China, with archaeological evidence indicating selective breeding for agricultural utility around 1000–2000 BCE. Genetic analyses confirm that major domestic breeds, including the Pekin duck, trace direct descent from mallard ancestors through interbreeding of wild populations and early captives, rather than significant input from other species like the spot-billed duck (Anas zonorhyncha). While some historical records suggest earlier utilization in Egypt dating to 4000 BCE, these likely involved opportunistic capture rather than systematic domestication, with genomic evidence prioritizing Asian origins for mallard-derived lineages. Selective breeding focused on enhancing traits for human provisioning, prioritizing larger body mass—domestic strains reaching 3–4 kg compared to 1–1.5 kg in wild mallards—for improved meat and fat yields, alongside plumage variations such as white feathering in breeds like the Pekin for easier management and processing. Egg production was markedly intensified, with selected lines achieving 150–300 eggs annually per hen versus the wild mallard's typical 10–15 viable eggs per breeding season across 1–2 clutches of 8–13 eggs each, driven by extended laying periods and reduced broodiness. These changes stemmed from practical imperatives for caloric efficiency in agrarian societies, where mallards' adaptability to captivity facilitated rapid genetic fixation of productivity traits under artificial selection. Genome-wide studies from 2021–2025, including high-quality assemblies of mallard and Pekin duck chromosomes, reveal selective sweeps on genes like MITF (for plumage) and those influencing reproduction, underscoring minimal admixture from non-mallard sources and validating the species' role as the progenitor of nearly all non-Muscovy domestic ducks. Escaped domestic stock has since contributed to feral populations worldwide, hybridizing with wild mallards and amplifying genetic diversity in managed lineages, though this reflects post-domestication dispersal rather than initial origins.

Utilization in hunting and sport

Mallards (Anas platyrhynchos) rank as one of the most sought-after species in waterfowl hunting across North America, prized for their abundance, distinctive behaviors, and responsiveness to hunting tactics. Hunters employ decoys arranged in resting or feeding configurations to simulate natural flocks on water, often combined with motion from jerk strings or spinning decoys to enhance realism. Acoustic lures include calls replicating hen mallard quacks for greeting, feeding, and comeback sequences, alongside drake whistles to evoke territorial responses, drawing birds within shotgun range during migration flights. Hunting seasons for mallards in the United States are regulated under the Migratory Bird Treaty Act, with frameworks established annually by the U.S. Fish and Wildlife Service allowing up to 107 days per state, typically split into segments aligned with fall and winter migrations to minimize impacts on breeding populations. Daily bag limits generally permit six ducks total, including no more than four mallards (two hens), varying by flyway and zone to reflect local abundance. These restrictions, informed by aerial surveys and banding data, ensure harvests remain sustainable, as evidenced by stable or rebounding eastern mallard numbers following 2019 adjustments. Revenues from federal duck stamps, required for hunters over 16, and excise taxes via the Pittman-Robertson Act channel billions into conservation, with the duck stamp program alone generating over $1.2 billion since 1934 for wetland acquisition and management benefiting mallard habitats. Waterfowl hunting contributes substantially to the $394 billion annual economic activity from hunting, fishing, and wildlife recreation, funding habitat restoration that supports broader biodiversity. Regulated mallard hunting fosters ecological stewardship among participants, who actively support wetland preservation—such as Ducks Unlimited's efforts in the Prairie Pothole Region—while harvest strategies employ yield models to prevent overpopulation strains on resources, countering ethical concerns with data demonstrating population resilience. The pursuit demands proficiency in camouflage, wind reading, and behavioral mimicry, yielding recreational and therapeutic benefits through outdoor engagement and tradition, without evidence of unsustainable declines attributable to sport harvest.

Culinary and nutritional value

Mallard meat serves as a lean protein source, with raw breast muscle typically containing about 20% protein and 2.0 g of lipid per 100 g, while leg meat averages 4.26 g of lipid per 100 g, making it lower in fat than domestic duck varieties. Compared to farmed ducks, wild mallard exhibits higher iron concentrations in both male and female specimens, alongside elevated lean meat yield exceeding 10-11% relative to intensively reared Pekin ducks. It is also rich in B vitamins, particularly B-12 essential for red blood cell formation, and iron, contributing to its nutritional profile as a nutrient-dense wild game option over factory-farmed poultry. The gamier flavor profile of wild mallard, influenced by its diverse natural diet, distinguishes it from milder domestic counterparts and suits preparation methods like high-heat roasting or pan-searing to medium-rare, preventing toughness from overcooking lean fibers. Historically, mallard has been a hunted staple in European and Asian cuisines since medieval times, featured in roasted preparations with sauces and valued for its availability across temperate regions. For food safety, given potential zoonotic pathogens in wild game birds, mallard should be cooked to an internal temperature of 165°F (74°C), verified with a food thermometer, to eliminate risks like salmonella or avian influenza, outperforming undercooked domestic poultry in pathogen load due to wild exposure but requiring vigilant handling. This practice aligns with USDA guidelines emphasizing thorough cooking for game birds to mitigate bacterial and parasitic hazards absent in controlled farm environments.

Cultural and symbolic roles

In Native American oral traditions, mallards and other ducks often appear as gullible or foolish figures in trickster tales, where they are outwitted by animals like Coyote or Fox due to their predictable foraging behaviors near water. This portrayal reflects observations of the bird's dabbling habits, which make it vulnerable to predation or deception in natural settings. The mallard's prolific breeding and migratory patterns have inspired symbols of fertility and freedom in European folklore, with its iridescent drake plumage evoking renewal tied to seasonal abundance. In literature, Robert McCloskey's Make Way for Ducklings (1941) centers on a female mallard navigating urban Boston with her brood, emphasizing maternal determination and family cohesion based on the species' real-world clutch sizes of 8–13 eggs. Anthropomorphic depictions amplify these traits in media; Disney's Donald Duck, debuting in the 1934 short The Wise Little Hen, derives from mallard morphology, including the green head and waddling gait, to satirize human foibles through exaggerated duck instincts like irritability during molt. The character's global popularity, spanning over 150 films and comics by 2023, stems from this foundation in observable mallard behaviors rather than abstract mysticism. English proverbs like "water off a duck's back," documented since the 19th century, draw from the mallard's preen gland oil that repels water from feathers, symbolizing resilience to criticism or hardship without deeper supernatural connotations.

Conflicts and mitigation

In urban environments, mallards frequently generate conflicts through excessive fouling of ponds, lawns, and recreational areas with feces, elevating health risks from pathogens like Salmonella and contributing to eutrophication of water bodies. Overfeeding by humans, often with nutritionally deficient bread, exacerbates these issues by promoting unnatural population densities, malnutrition (including "angel wing" deformities from protein imbalances), and heightened disease transmission via increased defecation and attraction of pests. Such practices have been documented in regions like Florida, where urban waterfowl concentrations strain local ecosystems and prompt public health advisories against supplemental feeding. Mallards also face and contribute to vehicle collisions, particularly when foraging along roadways near wetlands; a 2024 study found their flight initiation distances inadequate against approaching cars, with successful escapes below 20% at typical speeds, underscoring vulnerability in North American urban-rural interfaces. While property damage from trampling or nest-building remains minimal compared to larger waterfowl, cumulative aesthetic and maintenance costs burden municipalities. Mitigation emphasizes non-lethal hazing techniques, such as pyrotechnics, propane exploders, and visual deterrents, which USDA assessments confirm effectively disperse urban waterfowl flocks when integrated with habitat modifications like vegetation removal or water level adjustments, avoiding relocation that displaces issues elsewhere. These prioritize property protection under federal authorities for nuisance control, with trials showing sustained reductions in site use without habituation when methods rotate. For collision hotspots, infrastructure like underpasses, low fencing, and diversion poles guides waterbirds away from traffic, as recommended by U.S. Fish and Wildlife Service protocols.

References

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