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Mallard

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For other uses, see Mallard (disambiguation).

Mallard
Mallard female (front) and male (rear)
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Aves
Order:
Anseriformes
Family:
Anatidae
Subfamily:
Anatinae
Genus:
Anas
Species:
A. platyrhynchos
Binomial name
Anas platyrhynchos
Subspecies

See Mexican Duck, Anas and below

The Mallard (Anas platyrhynchos[1]), the archetypal "wild duck", is a dabbling duck which breeds throughout the temperate and sub-tropical areas of North America, Europe, Asia, New Zealand, and Australia. Probably the best-known and most recognizable of all ducks. Almost all of the varieties of domesticated ducks are descended from the Mallard (Anas platyrhynchos), apart from the Muscovy Duck[2][3].

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[4]. The Mallard is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies. Introduced into Australia and New Zealand, it is now the most common duck species in the latter country.

Description

Mallard drake in midflight
Female Mallard landing

The dabbling duck is 56–65 cm length, with an 81–98 cm wingspan, and weighs 750–1,000 g. The breeding male is unmistakable with a green head, black rear end and a yellow bill with a black tip (as opposed to the dark brown bill in females). The female Mallard is light brown, like most female dabbling ducks; however, both the female and male Mallards have distinct blue speculum edged with white, prominent in flight or at rest (though temporarily shedded during the annual summer molt). In non-breeding (eclipse) plumage, the drake becomes drab, looking more like the female, but still distinguishable by its bill, which remains yellow and its breast is more reddish.

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.

The size of the Mallard varies clinally, and birds from Greenland, although larger than birds further south, have smaller bills and are stockier. It is sometimes separated as subspecies Greenland Mallard (A. p. conboschas).

In captivity, domestic ducks come in wild-type plumages, white, and other colours. Most of these colour variants are also known in domestic mallards[5]; there they are rare but increasing in availability.

A noisy species, the male has a nasal call, the female the "quack" always associated with ducks. [6]

Ecology

The Mallard inhabits most wetlands, including parks, small ponds and rivers, and usually feeds by dabbling for plant food or grazing; there are reports of it eating frogs.[2] It usually nests on a river bank, but not always near water. It is highly gregarious outside of the breeding season and will form large flocks.

A 29-year-old Mallard has been recorded.[citation needed]

Breeding behaviour

An adult female with a brood of ducklings
A trio of ducklings
The new hatched ducklings are hiding under their mother.
A turtle and a brood of ducklings sharing microhabitat
A male Mallard resting on a log.

Mallards form pairs only until the female lays eggs, at which time she is left by the male. The clutch is 8–13 eggs, which are incubated for 27–28 days to hatching with 50–60 days to fledging. The ducklings are precocial, and can swim and feed themselves on insects as soon as they hatch, although they stay near the female for protection. Young ducklings are not naturally waterproof and rely on the mother to provide waterproofing. Mallards also have rates of male-male sexual activity that are unusually high for birds. In some cases, as many as 19% of pairs in a Mallard population are male-male homosexual[7].

When they pair off with mating partners, often one or several drakes will end up "left out". This group will sometimes target an isolated female duck — chasing, pestering and pecking at her until she weakens (a phenomenon referred to by researchers as rape flight), at which point each male will take turns brutally raping the female. Male Mallards will also occasionally chase other males in the same way. (In one documented case, a male Mallard anal raped another male he was chasing after it had been killed when it flew into a glass window[8].

Ancestor of almost all Domestic Ducks

Mallard (Anas platyrhynchos) is the ancestor of almost all of the varieties of domestic ducks. Domestic duck belong to the subfamily Anatinae of the waterfowl family Anatidae. The wild mallard and Muscovy duck (Cairina moschata) are believed to be the ancestors of all domestic ducks[9][10].

Genetic pollution, hybridization and systematics

Release of feral Mallard Ducks worldwide is creating havoc on indigenous waterfowl, these don't migrate and stay back in the local breeding season and interbreed with indigenous rare wild ducks devastating local populations of closely related species through genetic pollution by producing fertile offspring. Complete hybridization of various species of rare wild duck gene pools could result in the extinction of many indigenous waterfowl. Wild Mallard itself is the ancestor of most domestic ducks and their naturally evolved wild gene pool gets genetically polluted in turn by the domestic and feral populations[11][12][13][14][15].

Mallards frequently interbreed with their closest relatives in the genus Anas, such as the American Black Duck, and also with species more distantly related, for example the Northern Pintail, leading to various hybrids that may be fully fertile. This is quite unusual among different species, and apparently has its reasons in the fact that the Mallard evolved very rapidly and not too long ago, during the Late Pleistocene only. The distinct lineages of this radiation are usually kept separate due to non-overlapping ranges and behavioral cues, but are still not fully genetically incompatible. Mallards and their domesticated conspecifics are, of course, also fully interfertile.

The Mallard is considered an invasive species in New Zealand. There, and elsewhere, Mallards are spreading with increasing urbanization and hybridizing with local relatives[16]. Over time, a continuum of hybrids ranging between almost typical examples of either species will develop; the speciation process beginning to reverse itself[17]. This has created conservation concerns for relatives of the Mallard, such as the Hawaiian Duck[18], the New Zealand Grey Duck[19], the American Black Duck[20], the Florida Duck[21], Meller's Duck[22], the Yellow-billed Duck[17], and the Mexican Duck[23], in the latter case even leading to a dispute whether these birds should be considered a species[24] (and thus entitled to more conservation research and funding) or included in the mallard.

Like elsewhere worldwide the invasive alien mallard ducks are also causing severe “genetic pollution” of South Africa’s biodiversity by breeding with endemic ducks. The hybrids of mallard ducks and the Yellow billed duck are fertile and can produce more hybrid offspring. If this continues, only hybrids will occur and in the long term this will result in the extinction of various indigenous waterfowl worldwide like the yellow billed duck of South Africa. The mallard duck can cross breed with 45 other species and is posing a severe threat to the genetic integrity of indigenous waterfowls. Mallard ducks and their hybrids compete with indigenous birds for resources such as food, nest sites and roosting sites. The drakes (males) also kill the offspring of other waterfowl species by attacking and drowning them[25].

Drake, domestic duck × mallard, Akureyri (Iceland); note stocky body shape.

On the other hand, the Chinese Spotbill is currently introgressing into the mallard populations of the Primorsky Krai, possibly due to habitat changes from global warming[26]. The Mariana Mallard was a resident allopatric population - in most respects a good species - apparently initially derived from Mallard × Pacific Black Duck hybrids[27]; unfortunately, it became extinct in the 1980s. In addition, feral domestic ducks interbreeding with Mallards have led to a size increase - especially in drakes - in most Mallards in urban areas. Rape flights between normal-sized females and such stronger males are liable to end with the female being drowned by the males' combined weight.

It was generally assumed that as the spectacular nuptial plumage of Mallard drakes is obviously the result of sexual selection - most species in the mallard group being sexually monomorphic -, hybrid matings would preferentially take place between females of monomorphic relatives and Mallard drakes instead of the other way around. But this generalization was found to be incorrect.[28]

Note that it is not the hybridization itself that causes most conservation concerns. The Laysan Duck is an insular relative of the mallard with a very small and fluctuating population. Mallards sometimes arrive on its island home during migration, and can be expected to occasionally have remained and hybridized with Laysan Ducks as long as these species exist. But these hybrids are less well adapted to the peculiar ecological conditions of Laysan Island than the local ducks, and thus have lower fitness, and furthermore, there were - apart from a brief time in the early 20th century when the Laysan Duck was almost extinct - always much more Laysan Ducks than stray Mallards. Thus, in this case, the hybrid lineages would rapidly fail.

File:Anas oustaleti last male.gif
The last male Mariana Mallard. This extinct population probably evolved in part from mallards.

In the cases mentioned above, however, ecological changes and hunting have led to a decline of local species; for example, the New Zealand Gray Duck's population declined drastically due to overhunting in the mid-20th century (Williams & Basse 2006). In the Hawaiian Duck, it seems that hybrid offspring are less well-adapted to native habitat and that utilizing them in reintroduction projects makes these less than successful[29]. In conclusion, the crucial point underlying the problems of Mallards "hybridizing away" relatives is far less a consequence of Mallards spreading, but of local ducks declining; allopatric speciation and isolating behavior have produced today's diversity of Mallard-like ducks despite the fact that in most if not all of these populations, hybridization must always have occurred to some extent. Given time and a population of sufficient size exists, natural selection ought to suppress harmful allele combinations to a negligible level.

The aforementioned confounds analysis of the evolution considerably. Analyses of good samples of mtDNA sequences give the confusing picture[30] one expects from a wide-ranging species that has evolved probably not much earlier than the Plio-/Pleistocene boundary, around 2 mya. Mallards appear to be closer to their Indo-Pacific relatives than to their American ones judging from biogeography. Considering mtDNA D-loop sequence data[31], they may have evolved more probably than not 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. The large ice age paleosubspecies which made up at least the European and W Asian populations during the Pleistocene has been named Anas platyrhynchos palaeoboschas.

As expected, haplotypes typical of American mallard relatives and Spotbills can be found in Mallards around the Bering Sea[32]. Interestingly, the Aleutian Islands turned out to hold a population of Mallards that appear to be evolving towards a good subspecies as gene flow with other populations is very limited[33]. This unexpected result suggests that reevaluation of the Greenland, Iceland, and NE Canada populations according to molecular and morphological characters is warranted.

Notes and sources

Footnotes

  1. ^ Etymology: Ancient Greek for "flat-billed duck" [1]
  2. ^ Anas platyrhynchos, Domestic Duck; DigiMorph Staff - The University of Texas at Austin
  3. ^ Mallard; Encyclopædia Britannica
  4. ^ Herrera et al. (2006)
  5. ^ I.e., not bred as livestock, but kept as pets, aviary birds, etc.
  6. ^ Rogers (2001)
  7. ^ Bagemihl (1999)
  8. ^ Moeliker (2001). This paper was awarded with an Ig Nobel Prize in 2003 (MacLeod 2005).
  9. ^ Anas platyrhynchos, Domestic Duck; DigiMorph Staff - The University of Texas at Austin
  10. ^ Mallard; Encyclopædia Britannica
  11. ^ Mottled Ducks : The Problem – Hybridization; Florida Fish and Wildlife Conservation Commission, MyFWC.com
  12. ^ ENVIRONMENTAL ASSESSMENT FOR CONTROL OF FREE-RANGING RESIDENT MALLARDS IN FLORIDA, MAY 2002, Contact: Frank Bowers, U.S. Fish and Wildlife Service
  13. ^ Invasive Alien Bird Species Pose A Threat, Kruger National Park, Siyabona Africa Travel (Pty) Ltd - South Africa Safari Travel Specialist
  14. ^ Anas platyrhynchos, Domestic Duck; DigiMorph Staff - The University of Texas at Austin
  15. ^ Mallard; Encyclopædia Britannica
  16. ^ Rhymer & Simberloff (1996)
  17. ^ a b Rhymer (2006)
  18. ^ Griffin et al. (1989), Rhymer & Simberloff (1996)
  19. ^ Gillespie (1985), Rhymer et al. (1994), Rhymer & Simberloff (1996), Williams & Basse (2006).
  20. ^ Johnsgard (1967), Avise et al. (1990), Rhymer & Simberloff (1996), Mank et al. (2004).
  21. ^ Mazourek & Gray (1994), Rhymer & Simberloff (1996), McCracken et al. (2001).
  22. ^ Young & Rhymer (1998)
  23. ^ Rhymer & Simberloff (1996), McCracken et al. (2001)
  24. ^ See AOU (1983)
  25. ^ Invasive Alien Bird Species Pose A Threat, Kruger National Park, Siyabona Africa Travel (Pty) Ltd - South Africa Safari Travel Specialist
  26. ^ Kulikova et al. (2004)
  27. ^ Yamashina (1948)
  28. ^ Rhymer et al. (1994), Kulikova et al. (2004)
  29. ^ Rhymer & Simberloff (1996), see also Kirby et al. (2004)
  30. ^ See for example Johnson & Sorenson (1999) for a phylogeny suggesting Mallard paraphyly, almost certainly because one of the mere 2 Mallards successfully sampled had an American Black Duck maternal ancestor. Contrary to Avise et al. (1990), the question whether the American haplotypes are an original Mallard lineage is far from resolved[verification needed].
  31. ^ Kulikova et al. (2005)
  32. ^ Kulikova et al. (2004, 2005)
  33. ^ Kulikova et al. (2005)

References

  • American Ornithologists' Union (AOU) (1983): Check-list of North American Birds (6th edition). American Ornithologists' Union, Washington, DC.
  • Avise, John C.; Ankney, C. Davison & Nelson, William S. (1990): Mitochondrial Gene Trees and the Evolutionary Relationship of Mallard and Black Ducks. Evolution 44(4): 1109-1119. doi:10.2307/2409570 (HTML abstract and first page image)
  • Bagemihl, Bruce (1999): Biological Exuberance: Animal Homosexuality and Natural Diversity: 479-481. St. Martin's Press. ISBN 0312192398
  • Template:IUCN2006 Database entry includes justification for why this species is of least concern
  • Gillespie, Grant D. (1985): Hybridization, introgression, and morphometric differentiation between Mallard (Anas platyrhynchos) and Grey Duck (Anas superciliosa) in Otago, New Zealand. Auk 102 (3): 459-469. PDF fulltext
  • Griffin, C.R.; Shallenberger, F.J. & Fefer, S.I. (1989): Hawaii's endangered waterbirds: a resource management challenge. In: Sharitz, R.R. & Gibbons, I.W. (eds.): Proceedings of Freshwater Wetlands and Wildlife Symposium: 155-169. Savannah River Ecology Lab, Aiken, South Carolina.
  • Herrera, Néstor; Rivera, Roberto; Ibarra Portillo, Ricardo & Rodríguez, Wilfredo (2006): Nuevos registros para la avifauna de El Salvador. ["New records for the avifauna of El Salvador"]. Boletín de la Sociedad Antioqueña de Ornitología 16(2): 1-19. [Spanish with English abstract] PDF fulltext
  • Johnsgard, Paul A. (1967): Sympatry Changes and Hybridization Incidence in Mallards and Black Ducks. American Midland Naturalist 77(1): 51-63. doi:10.2307/2423425 (HTML abstract and first page image)
  • Johnson, Kevin P. & Sorenson, Michael D. (1999): Phylogeny and biogeography of dabbling ducks (genus Anas): a comparison of molecular and morphological evidence. Auk 116 (3): 792–805. PDF fulltext
  • Kirby, Ronald E.; Sargeant, Glen A. & Shutler, Dave (2004): Haldane's rule and American black duck × mallard hybridization. Canadian Journal of Zoology 82(11): 1827–1831. doi:10.1139/z04-169 (HTML abstract)
  • Kulikova, Irina V.; Zhuravlev, Yury N. & McCracken, Kevin G. (2004): Asymmetric hybridization and sex-biased gene flow between Eastern Spot-billed Ducks (Anas zonorhyncha) and Mallards (A. platyrhynchos) in the Russian Far East. Auk 121 (3): 930-949. [English with Russian abstract] DOI: 10.1642/0004-8038(2004)121[0930:AHASGF]2.0.CO;2 PDF fulltext
  • Kulikova, Irina V.; Drovetski, S.V.; Gibson, D.D.; Harrigan, R.J.; Rohwer, S.; Sorenson, Michael D.; Winker, K.; Zhuravlev, Yury N. & McCracken, Kevin G. (2005): Phylogeography of the Mallard (Anas platyrhynchos): Hybridization, dispersal, and lineage sorting contribute to complex geographic structure. Auk 122 (3): 949-965. [English with Russian abstract] DOI: 10.1642/0004-8038(2005)122[0949:POTMAP]2.0.CO;2 PDF fulltext. Erratum: Auk 122 (4): 1309. DOI: 10.1642/0004-8038(2005)122[0949:POTMAP]2.0.CO;2
  • MacLeod, Donald (2005): Necrophilia among ducks ruffles research feathers. Education Guardian (March 8). Retrieved 2006-DEC-09.
  • Mank, Judith E.; Carlson, John E. & Brittingham, Margaret C. (2004): A century of hybridization: Decreasing genetic distance between American black ducks and mallards. Conservation Genetics 5(3): 395–403. doi:10.1023/B:COGE.0000031139.55389.b1 (HTML abstract)
  • Mazourek, J.C. & Gray, P.N. (1994): The Florida duck or the mallard? Florida Wildlife 48 (3): 29-31. DOC fulltext
  • McCracken, Kevin G.; Johnson, William P. & Sheldon, Frederick H. (2001): Molecular population genetics, phylogeography, and conservation biology of the mottled duck (Anas fulvigula). Conservation Genetics 2 (2): 87–102. doi:10.1023/A:1011858312115 PDF fulltext
  • Moeliker, C. W. "Kees" (2001): The first case of homosexual necrophilia in the Mallard Anas platyrhynchos (Aves: Anatidae). Deinsea 8: 243-247. PDF fulltext
  • Rhymer, Judith M. (2006): Extinction by hybridization and introgression in anatine ducks. Acta Zoologica Sinica 52(Supplement): 583–585. PDF fulltext
  • Rhymer, Judith M. & Simberloff, Daniel (1996): Extinction by hybridization and introgression. Annu. Rev. Ecol. Syst. 27: 83-109. doi:10.1146/annurev.ecolsys.27.1.83 (HTML abstract)
  • Rhymer, Judith M.; Williams, Murray J. & Braun, Michael J (1994). Mitochondrial analysis of gene flow between New Zealand Mallards (Anas platyrhynchos) and Grey Ducks (A. superciliosa). Auk 111 (4): 970–978. PDF fulltext
  • Rogers, D. (2001): Animal Diversity Web: Anas platyrhynchos. Retrieved 2006-DEC-08.
  • Williams, Murray & Basse, Britta (2006): Indigenous gray ducks, Anas superciliosa, and introduced mallards, A. platyrhynchos, in New Zealand: processes and outcome of a deliberate encounter. Acta Zoologica Sinica 52(Supplement): 579–582. PDF fulltext
  • Yamashina, Y. (1948): Notes on the Marianas mallard. Pacific Science 2: 121-124.
  • Young, H. Glyn & Rhymer, Judith M. (1998): Meller's duck: A threatened species receives recognition at last. Biodiversity and Conservation 7: 1313-1323. doi:10.1023/A:1008843815676
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