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A 29-year-old mallard has been recorded.{{cn}}
A 29-year-old mallard has been recorded.{{cn}}


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==Breeding behaviour==
[[Image:Female mallard nest - natures pics edit2.jpg|thumb|250px|Female with a brood of ducklings]]
:''See also'' [[animal sexuality]]
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 (Bagemihl 1999).

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 copulating with the female. Male Mallards will also occasionally chase other males in the same way. (In one documented case, a male Mallard copulated with another male he was chasing after it had been killed when it flew into a glass window (Moeliker 2001 <ref>
This paper was awarded with an [[Ig Nobel Prize]] in [[2003]] (MacLeod 2005)</ref>).

===Hybridization and systematics===
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 [[hybrid]]s that may be fully fertile. This is quite unusual among different species, and apparently has its reasons in the fact that the mallard group [[evolution|evolved]] vaery 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 [[behavior]]al cues, but are still not fully genetically incompatible. Mallards and their domesticated [[conspecific]]s 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. Over time, a continuum of hybrids ranging between almost typical examples of either species will develop; the [[speciation]] process beginning to reverse itself. This has created [[Conservation biology|conservation]] concerns for relatives of the mallard, such as the [[Hawaiian Duck]], the [[New Zealand Grey Duck]] (Gillespie 1985), the American Black Duck, the [[Florida Duck]] (McCracken ''et al.'' 2001), [[Meller's Duck]] and the [[Mexican Duck]], in the latter case even leading to a dispute whether these birds should be considered a species (and thus entitled to more conservation research and funding) or included in the mallard.

[[Image:Snow crystallization in Akureyri 2005-02-26 15-57-55.jpeg|thumb|250px|left|Hybrid Mallard × Domestic duck drake in [[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]] (Kulikova ''et al.'' 2004). The [[Mariana Mallard]] was a population - in most repects a good species - apparently initially derived from Mallard × [[Pacific Black Duck]] hybrids (Yamashina 1948); 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 frequently end in 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 [[sexual dimorphism|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 has proven to be incorrect (Rhymer ''et al.'' 1994, Kulikova ''et al.'' 2004).

Note that it is not the hybridization itself that causes 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 (biology)|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.

In the cases mentioned above, however, ecological changes and hunting have led to a decline of local species. Thus, 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.

The aforementioned confounds analysis of the evolution considerably. Analyses of good samples of [[mtDNA]] [[DNA sequence|sequence]]s give the confusing picture<ref>
See for example Johnson & Sorenson (1999) for a phylogeny suggesting Mallard [[paraphyly]], almost certainly because one of the 2(!) Mallards successfully sampled had an American Black Duck maternal ancestor.</ref>
one expects from a wide-ranging species that has evolved probably not much earlier than the [[Pliocene|Plio-]]/[[Pleistocene]] boundary, around 2 [[mya (unit)|mya]]. Mallards appear to be closer to their [[Indo-Pacific]] relatives than to their American ones judging from [[biogeography]]. Considering [[mtDNA]] [[control region]] [[DNA sequence|sequence]] data (Kulikova ''et al.'' 2005), 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''.<!-- CRAcadSciIIA327:341 -->

As expected, [[haplotypes]] typical of American mallard relatives and Spotbills can be found in Mallards around the [[Bering Sea]] (Kulikova ''et al.'' 2004, 2005). 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 (Kulikova ''et al.'' 2005). This unexpected result suggests that reevaluation of the Greenland, [[Iceland]], and NE [[Canada]] populations according to molecular and morphological characters is warranted.

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==Photo gallery==
==Photo gallery==

Revision as of 01:41, 11 December 2006

For other uses, see Mallard (disambiguation).

Mallard
Two mallard drakes and one female
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 article text

The mallard (Anas platyrhynchos[1]), also known as the wild duck in North America, is a dabbling duck which breeds throughout the temperate and sub-tropical areas of North America, Europe and Asia. Probably the best-known of all ducks, it gave rise to most domestic ducks, apart from the Muscovy Duck.

It is strongly migratory in the northern parts of its breeding range, and winters farther south; it is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies. It also frequents Central America and the Caribbean, and has been introduced into Australia and New Zealand. It is now the most common duck in New Zealand.

In captivity, mallards come in wild-type plumages, white, and other colours. Most of these colour variants are rare but increasing in domestic collections.

Mallards are hunted and eaten as game. The flesh has a stonger flavour than that of the more commonly eaten domestic ducks. [2]

Description

Mallard drake in midflight

The dabbling duck is 56–65 cm length, with an 81–98 cm wingspan, and weighs 750–1000 g. The breeding male is unmistakable with a green head, black rear end and a blue speculum edged with white, prominent in flight or at rest. Males also possess a yellow bill with a black tip, females dark brown.

The female mallard is light brown like most female dabbling ducks. It can be distinguished from other ducks by the distinctive speculum. In non-breeding (eclipse) plumage, the drake looks more like the female.

Female Mallard landing

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).

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. They are exceptionally fast flyers for their size, reaching speeds of 65 km/h (40 mph).

A noisy species, the male has a nasal call, the female the "quack" always associated with ducks. (Rogers 2001)

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

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Wikimedia Commons has media related to Anas platyrhynchos.

References

  • 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
  • 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
  • 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
  • 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.; 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
  • Yamashina, Y. (1948): Notes on the Marianas mallard. Pacific Science 2: 121-124.

Footnotes

  1. ^ Etymology: Ancient Greek for "flat-billed duck" [1]
  2. ^ "Waitrose.com Food Glossary," Accessed November 8 2006
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