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Nov 15 2011

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Falkland Steamer Duck (Tachyeres brachypterus)


Falkland Steamer Duck

[order] ANSERIFORMES | [family] Anatidae | [latin] Tachyeres brachypterus | [authority] Gmelin, 1789 | [UK] Falkland Steamer Duck | [FR] Brassemer des Malouines | [DE] Falkland-Dampfschiffente | [ES] Quetro Malvinero (Arg) | [NL] Falklandbooteend

Subspecies

Genus Species subspecies Region Range
Tachyeres brachypterus SA Falkland Islands

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 characteristics
The male is larger and paler overall. In general, he is grey or white about the head, while the females head is brown with a white eye-ring and a thin while line curving from the eye down the side of the head. Young males and some adult males in moult may also have a white line behind the eye, but this is less clear-cut. The bill of an adult male is bright orange, with a prominent black tip. The female bill is greenish-yellow. The male is large – one of the biggest ducks in the world. An adult drake may weigh around 3½ kg and measure 80cms from the tip of his bill to the end of his tail. Both sexes, when adult, have orange-yellow legs and feet. Those of immature birds, of either sex, are paler and have black marks at the heel and toe joints. All individuals have spurs, bare of feathers, at the angle of the wing. An adult male defending territory will have well-developed, bright orange spurs, which he will use to good effect in violent combat with other males.
Habitat
This species frequents rugged shorelines, being most common on small islands and in sheltered bays. The bulk of its diet is a variety of salt-water molluscs and crustaceans, which it obtains my foraging in shallow water or diving in near shore. Its breeding season is variable, but most breeding occurs between September and December, concealing nests among vegetation or in unoccupied penguin burrows
Other details
The Falkland Steamer Duck is flightless, but it can race speedily over the water, propelling itself with both wings and feet. It does this in a large cloud of spray, as its breast ploughs the water like the prow of a ship. Its wings are perfectly formed but when folded are shorter than its body.
Feeding
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.
Conservation
Although this species may have a restricted range, it is not believed to approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size may be moderately small to large, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern. [conservation status from birdlife.org]

Breeding
It hides its nest in long grass or diddle-dee; occasionally in dry kelp tangles, old penguin burrows or jumbled boulders. The nest itself is a slight hollow in the ground lined with grass and soft down feathers. It is usually within easy sprinting distance of the seashore, but nests have been found up to 400 metres from the sea. Typically, the bird lays 5 – 8 eggs, rarely more. Nests with eggs have been found in most months of the year, but mainly in the period September – December. The female alone does all the incubation, as is usual with duck species. She will leave the nest to bathe and preen for 15 – 30 minutes each day, covering her eggs with nest materials before she goes. It is not known if she feeds at all when on eggs. The incubation period is thought to be 26 – 30 days from when the last egg is laid. While the female remains hidden on the nest, the male patrols the territory and chases away all-comers.
Migration
As would be expected from its name, this flightless duck is endemic to the Falklands.
Distribution map
Falkland Steamer Duck

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