The Falkland steamer duck (Tachyeres brachypterus) is a species of flightless duck found on the Falkland Islands in the South Atlantic Ocean. The steamer ducks get their name from their unconventional swimming behaviour in which they flap their wings and feet on the water in a motion reminiscent of an old paddle steamer. The Falkland steamer duck is one of only two bird species endemic to the Falkland Islands, the other being Cobb's wren.
Taxonomy and systematics
The Falkland steamer duck is part of the order Anseriformes and the family Anatidae, alongside ducks, geese, and swans. It is in the genus Tachyeres with the three other species of steamer ducks, all found in South America. The Falkland steamer duck is most closely related to the flying steamer duck, which can also be found in and around the Falkland Islands. It is believed that they might still be able to interbreed. A study from 2012 established that these two species are genetically indistinguishable. Possible hybridization could account for the genetic similarities between the two species. Some scientists have proposed that the flying steamer duck and the Falkland steamer duck should be a single species, but more evidence is needed to settle that question.
Evolution of flightlessness
Steamer ducks are a young group from an evolutionarily point of view and have a last common ancestor believed to have lived about 2 million years ago. In short, the Falkland steamer duck is a promising model organism to study and understand the process behind the evolution of flightlessness in birds.
Description
thumb|left|Falkland steamer duck pair at Whale Bone Cove, Falkland Islands.
thumb| Tachyeres brachypterus - [[MHNT]]
The Falkland steamer duck measures between 61 and 74 cm in length and has a wingspan of 84 to 94 cm. It is a fairly large species of duck with males weighing between 3300 and 4800 g, and females between 2900 and 4196 g. Finally, as its name implies, the flying steamer duck is capable of flight while the Falkland steamer duck is strictly flightless. This last characteristic is difficult to see in the field because the flying steamer duck seldom flies and is often seen walking or swimming.
Historical description
Charles Darwin devoted two paragraphs to this bird (or the similar flying steamer duck) in The Voyage of the Beagle, having observed them at the Falkland Islands in 1833:
Habitat and distribution
thumb|The Falkland steamer duck is primarily found on rugged coastlines.
The species' distribution is limited to the Falkland Islands in the South Atlantic Ocean. These ducks are year-round residents of the islands and the surrounding archipelago, and can be found mainly on rugged shores and in sheltered bays. Another possible source of concern comes from oil spills. The species has a limited distribution, and its food supply could be severely affected by a large-scale release of oil in and around the Falklands.