Anatra muta

Identificazione

All Muscovy ducks have long claws on their feet and a wide, flat tail. In the domestic drake (male), length is about 86 cm (34 in) and weight is 4.6–6.8 kg (10–15 lb), while the domestic hen (female) is much smaller, at 64 cm (25 in) in length and 2.7–3.6 kg (6.0–7.9 lb) in weight. Large domesticated males often weigh up to 7 kg (15 lb), and large domesticated females up to 4 kg (8.8 lb).<p>The true wild Muscovy duck, from which all domestic Muscovies originated, is blackish, with large white wing patches. Length can range from 66 to 84 cm (26 to 33 in), wingspan from 137 to 152 cm (54 to 60 in) and weight from 1.1 to 4.1 kg (2.4 to 9.0 lb). On the head, the wild male has a short crest on the nape. The bill is black with a speckling of pale pink. A blackish or dark red knob can be seen at the bill base, which is similar in colour to the bare skin of the face. The eyes are yellowish-brown. The legs and webbed feet are blackish. The wild female is similar in plumage, but much smaller, with a feathered face and lacking the prominent knob. The juvenile is duller overall, with little or no white on the upperwing.<p>Domesticated birds may look similar; most are dark brown or black mixed with white, particularly on the head. Other colors, such as lavender or all-white, are also seen. Both sexes have a nude black-and-red or all-red face; the drake also has pronounced caruncles at the base of the bill and a low erectile crest of feathers. C. moschata ducklings are mostly yellow with buff-brown markings on the tail and wings. For a while after hatching, juveniles lack the distinctive wattles associated with adult individuals, and resemble the offspring of various other ducks, such as mallards. Some domesticated ducklings have a dark head and blue eyes, others a light brown crown and dark markings on their nape. They are agile and speedy precocial birds.<p>The drake has a low breathy call, and the hen a quiet trilling coo.<p>The karyotype of the Muscovy duck is 2n=80, consisting of three pairs of macrochromosomes, 36 pairs of microchromosomes, and a pair of sex chromosomes. The two largest macrochromosome pairs are submetacentric, while all other chromosomes are acrocentric or probably telocentric for the smallest microchromosomes. The submetacentric chromosomes and the Z (female) chromosome show rather little constitutive heterochromatin (C bands), while the W chromosomes are at least two-thirds heterochromatin.<p>Male Muscovy ducks have helical penises that become erect to 19 cm (7 in) in 0.3 s. Females have vaginas that coil in the opposite direction that appear to have evolved to limit forced copulation by males.

Tassonomia

The species was first scientifically described by Carl Linnaeus in his 1758 edition of Systema Naturae as Anas moschata, literally meaning "musk duck". It was later transferred to the genus Cairina, making its current binomial name Cairina moschata.<p>The Muscovy duck was formerly placed into the paraphyletic "perching duck" assemblage, but subsequently moved to the dabbling duck subfamily (Anatinae). Analysis of the mtDNA sequences of the cytochrome b and NADH dehydrogenase subunit 2 genes, however, indicates that it might be closer to the genus Aix and better placed in the shelduck subfamily Tadorninae. In addition, the other species of Cairina, the rare white-winged duck (C. scutulata), seems to belong to a distinct genus (Asarcornis).

Nome scientifico

Cairina moschata

Autorità

(Linnaeus, 1758)

Ordine

Anseriformi

Famiglia

Anatidae

Genere

Cairina

Areale e habitat

Migrazione

Resident species

Comportamento

This non-migratory species normally inhabits forested swamps, lakes, streams and nearby grassland and farm crops, and often roosts in trees at night. The Muscovy duck's diet consists of plant material (such as the roots, stems, leaves, and seeds of aquatic plants and grasses, as well as terrestrial plants, including agricultural crops) obtained by grazing or dabbling in shallow water, and small fish, amphibians, reptiles, crustaceans, spiders, insects, millipedes, and worms. This is an aggressive duck; males often fight over food, territory or mates. The females fight with each other less often. Some adults will peck at the ducklings if they are eating at the same food source.<p>The Muscovy duck has benefited from nest boxes in Mexico, but is somewhat uncommon in much of the eastern part of its range due to excessive hunting. It is not considered a globally threatened species by the IUCN, however, as it is widely distributed.<p>This species, like the mallard, does not form stable pairs. They will mate on land or in water. Domestic Muscovy ducks can breed up to three times each year.<p>The hen lays a clutch of 8–16 white eggs, usually in a tree hole or hollow, which are incubated for 35 days. The sitting hen will leave the nest once a day from 20 minutes to one and a half hours, and will then defecate, drink water, eat and sometimes bathe. Once the eggs begin to hatch, it may take 24 hours for all the chicks to break through their shells. When feral chicks are born, they usually stay with their mother for about 10–12 weeks. Their bodies cannot produce all the heat they need, especially in temperate regions, so they will stay close to the mother, especially at night.<p>Often, the drake will stay in close contact with the brood for several weeks. The male will walk with the young during their normal travels in search for food, providing protection. Anecdotal evidence from East Anglia, U.K. suggests that, in response to different environmental conditions, other adults assist in protecting chicks and providing warmth at night. It has been suggested that this is in response to local efforts to cull the eggs, which has led to an atypical distribution of males and females, as well as young and mature birds.<p>For the first few weeks of their lives, Muscovy chicks feed on grains, corn, grass, insects, and almost anything that moves. Their mother instructs them at an early age how to feed.<p>Feral Muscovy ducks can breed near urban and suburban lakes and on farms, nesting in tree cavities or on the ground, under shrubs in yards, on apartment balconies, or under roof overhangs. Some feral populations, such as that in southern Florida, have a reputation of becoming pests on occasion. At night they often sleep at water, if there is a water source available, to flee quickly from predators if awakened. Small populations of Muscovy ducks can also be found in Ely, Cambridgeshire, Calstock, Cornwall, and Lincoln, Lincolnshire, U.K. Muscovy ducks have also been spotted in the Walsall Arboretum. There has been a small population in the Pavilion Gardens public park in Buxton, Derbyshire for many years.<p>In the U.S., Muscovy ducks are considered a non-native species. An owner may raise them for food production only (not for hunting). Similarly, if the ducks have no owner, 50CFR Part 21 (Migratory Bird Permits) allows the removal or destruction of the ducks, their eggs and their nests anywhere in the United States outside of Hidalgo, Starr and Zapata Counties in Texas, where they are considered indigenous. The population in southern Florida is considered, with numbers in the several thousands, to be established enough to be considered "countable" for bird watchers.<p>Legal methods to restrict breeding include not feeding these ducks, deterring them with noise or chasing them away.<p>Although legislation passed in the U.S. prohibiting trade of Muscovy ducks, Fish and Wildlife Services intend to revise the regulations. They are not currently implementing them, though release of Muscovy ducks to the wild outside their natural range is prohibited.

Conservazione

Tendenza della popolazione

declining