Mexican Duck
Encyclopedia
The Mexican Duck is a dabbling duck in the genus Anas which breeds in Mexico
and the southern USA. Most of the population is resident, but some northern birds migrate
south to Mexico in winter.
It is a bird of most wetlands, including pond
s and rivers, and usually feeds by dabbling for plant food or grazing. It nests usually on a river bank, but not always particularly near water.
Both sexes of this 51–56 cm length bird
resemble a female Mallard
, but with a slightly darker body. The Mexican Duck is mainly brown, with a blue speculum
edged with white, obvious in flight or at rest. The male has a brighter yellow bill than the female.
The male has a nasal call, whereas the female has the very familiar "quack" commonly associated with ducks.
This species was formerly - and sometimes still is - considered a subspecies
of the Mallard, as Anas platyrhynchos diazi (AOU 1983). This may not be correct, however, as careful analysis of mtDNA control region sequence
data - taking into account hybridization events - indicates it is the southwestern relative of the American Black Duck
and shares a fairly recent common ancestry with this species (McCracken et al. 2001).
Including the Mexican Duck in the Mallard is a relict from the usual practice of much of the mid-late 20th century, when all North America
n "mallardines" as well as the Hawaiian
and Laysan Duck
s were included in the Mallard proper as subspecies. This was based on the assumption that hybridization, producing fertile
offsprings, is an indicator of lack of speciation
.
Rather, in these birds it indicates a fairly recent allopatric radiation
, which has not yet established solid barriers against gene flow
on the molecular level; mate choice
is conferred by cues of behavior
and plumage in the mallardine ducks, and this, under natural conditions, has precluded a strong selective
pressure towards establishment of genetic incompatibility.
and overhunting. It hybridizes with Mallards which are better-adapted to utilizing habitat altered by human activity and thus are spreading throughout this range. Concern has been expressed that this combination of factors may ultimately lead to the disappearance of the Mexican Duck as a recognizable taxonomic
entity (Rhymer & Simberloff 1996, McCracken et al. 2001, Rhymer 2006), but fairly limited measures such as wetland preservation and preferential hunting of drake mallards would prevent this. The Mexican Duck was listed as endangered species at the United States Fish and Wildlife Service
in 1967 but was removed in 1978.
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
and the southern USA. Most of the population is resident, but some northern birds migrate
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
south to Mexico in winter.
It is a bird of most wetlands, including pond
Pond
A pond is a body of standing water, either natural or man-made, that is usually smaller than a lake. A wide variety of man-made bodies of water are classified as ponds, including water gardens, water features and koi ponds; all designed for aesthetic ornamentation as landscape or architectural...
s and rivers, and usually feeds by dabbling for plant food or grazing. It nests usually on a river bank, but not always particularly near water.
Both sexes of this 51–56 cm length bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
resemble a female Mallard
Mallard
The Mallard , or Wild Duck , is a dabbling duck which breeds throughout the temperate and subtropical Americas, Europe, Asia, and North Africa, and has been introduced to New Zealand and Australia....
, but with a slightly darker body. The Mexican Duck is mainly brown, with a blue speculum
Speculum feathers
The speculum is a patch, often distinctly coloured, on the inner remiges of some birds.Examples of the colour of the speculum in a number of ducks are:* Common Teal and Green-winged Teal: Iridescent green edged with buff....
edged with white, obvious in flight or at rest. The male has a brighter yellow bill than the female.
The male has a nasal call, whereas the female has the very familiar "quack" commonly associated with ducks.
This species was formerly - and sometimes still is - considered a subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of the Mallard, as Anas platyrhynchos diazi (AOU 1983). This may not be correct, however, as careful analysis of mtDNA control region sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
data - taking into account hybridization events - indicates it is the southwestern relative of the American Black Duck
American Black Duck
The American Black Duck is a large dabbling duck. American Black Ducks are similar to Mallards in size, and resemble the female Mallard in coloration, although the Black Duck's plumage is darker...
and shares a fairly recent common ancestry with this species (McCracken et al. 2001).
Including the Mexican Duck in the Mallard is a relict from the usual practice of much of the mid-late 20th century, when all North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n "mallardines" as well as the Hawaiian
Hawaiian Duck
The Hawaiian Duck is a species of bird in the family Anatidae. It is endemic to the large islands of Hawaii. Some authorities treat it as an island subspecies of the Mallard, based on their capacity to produce fertile hybrids, but it appears well distinct and capability of hybridization is...
and Laysan Duck
Laysan Duck
The Laysan Duck , also known as the Laysan Teal because of its small size, is an endangered dabbling duck endemic to the Hawaiian Islands...
s were included in the Mallard proper as subspecies. This was based on the assumption that hybridization, producing fertile
Fertile
The term fertile describes a condition whereby organisms are able to produce physically healthy offspring.Fertile may also refer to:...
offsprings, is an indicator of lack of speciation
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
.
Rather, in these birds it indicates a fairly recent allopatric radiation
Adaptive radiation
In evolutionary biology, adaptive radiation is the evolution of ecological and phenotypic diversity within a rapidly multiplying lineage. Starting with a recent single ancestor, this process results in the speciation and phenotypic adaptation of an array of species exhibiting different...
, which has not yet established solid barriers against gene flow
Gene flow
In population genetics, gene flow is the transfer of alleles of genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies...
on the molecular level; mate choice
Mate choice
Mate choice, or intersexual selection, is an evolutionary process in which selection of a mate depends on attractiveness of its traits. It is one of two components of sexual selection...
is conferred by cues of behavior
Behavior
Behavior or behaviour refers to the actions and mannerisms made by organisms, systems, or artificial entities in conjunction with its environment, which includes the other systems or organisms around as well as the physical environment...
and plumage in the mallardine ducks, and this, under natural conditions, has precluded a strong selective
Selection
In the context of evolution, certain traits or alleles of genes segregating within a population may be subject to selection. Under selection, individuals with advantageous or "adaptive" traits tend to be more successful than their peers reproductively—meaning they contribute more offspring to the...
pressure towards establishment of genetic incompatibility.
Conservation status
Although a species of least concern, the Mexican Duck is undergoing a slow but marked decline due to destruction of habitatHabitat (ecology)
A habitat is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism...
and overhunting. It hybridizes with Mallards which are better-adapted to utilizing habitat altered by human activity and thus are spreading throughout this range. Concern has been expressed that this combination of factors may ultimately lead to the disappearance of the Mexican Duck as a recognizable taxonomic
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
entity (Rhymer & Simberloff 1996, McCracken et al. 2001, Rhymer 2006), but fairly limited measures such as wetland preservation and preferential hunting of drake mallards would prevent this. The Mexican Duck was listed as endangered species at the United States Fish and Wildlife Service
United States Fish and Wildlife Service
The United States Fish and Wildlife Service is a federal government agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats...
in 1967 but was removed in 1978.