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Nov 12 2011

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Chubut Steamer Duck (Tachyeres leucocephalus)

Chubut Steamer Duck

[order] ANSERIFORMES | [family] Anatidae | [latin] Tachyeres leucocephalus | [authority] Humphrey and Thompson, 1981 | [UK] Chubut Steamer Duck | [FR] Brassemer a tete blanche | [DE] Weisskopf-Dampfschiffente | [ES] Patovapor Cabeciblanco | [NL] Witkopbooteend

Subspecies

Monotypic species

Genus

The steamer ducks are a genus (Tachyeres) of ducks in the family Anatidae. All of the four species occur in South America, and all except the Flying Steamer Duck are flightless; even this one species capable of flight rarely takes to the air. The common name “steamer ducks” derives because, when swimming fast, they flap their wings into the water as well as using their feet, creating an effect like a paddle steamer. They are usually placed in the shelduck subfamily Tadorninae. However, mtDNA sequence analyses of the cytochrome b and NADH dehydrogenase subunit 2 genes indicate that Tachyeres rather belongs into a distinct clade of aberrant South American dabbling ducks, which also includes the Brazilian, the Crested, and the Bronze-winged Ducks.

Physical charateristics

Head mostly white, forehead and crown light gray, becoming paler at the back and slightly mottled with pale cinnamon where wear has exposed the bases of the feathers; lores light gray, mottled with medium dusky brown and pearl gray feathers; upper and lower eyelids white; chin and neck white; small light chestnut patch on throat becomng slightly paler towards the back; mantle, scapulars, back, rump, upper tail coverts, sides, and flanks predominantly medium pearl gray becoming paler on the upper back; most of the mantle feathers and scapulars with paler, silvery gray patches around the dark rachis and darker gray (sometimes dusky) margins, giving a scaled appearance; upper breast medium pearl gray, becoming more dusky brown towards the center, with scattered light to medium chestnut where feather bases show; feathers of upper breast and sides of breast with narrow, pale smoke gray margins; feathers of the sides and flanks with a silvery or slightly metallic pale pearl gray wash, narrowly tipped with medium chestnut or pale smoke gray on the older, more worn feathers. Lower breast, abdomen, and under-tail coverts white.Primaries and greater upper primary coverts dark dusky brown with blackish brown shafts; rest of upper wing medium fuscous, some (newer) feathers darker and others (worn) very pale buffy brown. Secondaries white, the inner vane of the innermost medium blackish-brown; tertials medium dusky brown, paler at the edges; innermost tertials quite worn, their frayed edges being very pale, almost whitish, buffy brown. Axillaries and central part of wing lining white; balance of underwing coverts medium dusky brown, the greater under primary coverts paler. Rectrices dark blackish brown, with black shaft and faint mesial wash of light silvery gray. Iris brown; bill orange, becoming greenish at tomium and yellowish near tip, the nail black; legs and feet bright yellow with claws blackish.


wingspan min.: 0 cm wingspan max.: 0 cm
size min.: 61 cm size max.: 74 cm
incubation min.: 28 days incubation max.: 30 days
fledging min.: 120 days fledging max.: 130 days
broods: 1   eggs min.: 3  
      eggs max.: 6  

Range

South America : Southeast Argentina. Tachyeres leucocephalus was previously considered to be restricted to the south coast of Chubut province, Argentina. It is now known to have a larger range, with occasional signtings along the coastline from the Valdes Peninsula to the Beagle Channel in Tierra del Fuego.

Habitat

It is entirely coastal in rocky areas and sheltered bays, breeding on offshore islands and peninsulas.

Reproduction

Nest is built on the ground near water, on peninsulas or islands, concealed in vegetation, it is well lined with down. Clutch size is 3-6 eggs which are incubated by the female just short of a month. Young fledge after about 120-130 days. Built solitary nests, but dense colonies on offshore islands. Both parents care for the young once hatched. Aggressively defend small territories while breeding.

Feeding habits

Steamer ducks feed on a variety of small marine animals living on the seabed. They will upend to feed in very shallow water, but mainly they dive to secure their prey. They use both wings and feet to propel themselves underwater. When one bird from a large flock dives, often most of the others go down at the same time. They will emerge almost simultaneously 20-40 seconds later, bouncing to the surface like a lot of corks. No detailed studies of the ducks’ diet have been undertaken, but we know that mussels are a favourite item and that they also eat other bivalves, sea-snails, limpets, shrimps and crabs.

Video Chubut Steamer Duck

httpv://www.youtube.com/watch?v=CcqHNo9qJKM

copyright: Anna Motis


Conservation

This species is classified as Near Threatened as it has a small population within which all individuals are restricted to one sub-population. Any evidence of a decline is likely to cause the species to be uplisted to Vulnerable.
There are no known threats at present, but its restricted range, flightlessness and the potential for oil pollution from passing tankers put this species at some risk. Although locally abundant, not described until 1981; old records of occurrence of T. pteneres on Chubut coast presumably refer to present species. Often considered to form superspecies with T. pteneres and T. brachypterus.
Chubut Steamer Duck status Near Threatened

Migration

Sedentary, is a flightless duck but may move in the vicienty of breeding ground.

Distribution map

Chubut Steamer Duck distribution range map

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