They are called "steamer-ducks" because when swimming they look like a paddle steamboat as they splash their wings and feet. . This species is endemic to the Falkland Islands. Flying populations breeding on inland lakes have been assumed to be a different species, the Flying Steamer Duck (T. patachonicus) which also occurs in Southern South America. However a recent study (Fulton et al. 2012) found that the flying birds on the Falklands are “genetically indistinguishable” from the flightless ones. They suggest that all the Steamer-Ducks on the Falklands, flying and flightless may belong to a single species. Plumage-wise, the two types are similar although flightless birds reportedly average a heavier neck, shorter wings and tail, and stouter bill. Males have bright orange bills while females have dull greenish olive yellow bills. IOC and Howard & Moore remove the hyphen in its English name while HBW and Birdlife International compound the specific name resulting in "Falkland Steamerduck." Canon PowerShot SX50 HS
References:
Carboneras, C. & Kirwan, G.M. (2018). Falkland Steamerduck (Tachyeres brachypterus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/52843 on 26 May 2018).
Dickinson, EC, ed. 2014. The Howard and Moore Complete Checklist of the Birds of the World. 4th ed. Princeton: Princeton Univ. Press. ISBN 978-0956861122
Fulton, T.L., Letts, B. & Shapiro, B. (2012) Multiple losses of flight and recent speciation in steamer ducks. Proc. Royal Soc. London (Ser. B Biol. Sci.) 279: 2339–2346.
Gill, F & D Donsker (Eds). 2018. IOC World Bird List (v8.1). doi : 10.14344/IOC.ML.8.1. Available at http://www.worldbirdnames.org/.
Remsen, J. V., Jr., J. I. Areta, C. D. Cadena, S. Claramunt, A. Jaramillo, J. F. Pacheco, M. B. Robbins, F. G. Stiles, D. F. Stotz, and K. J. Zimmer. Version [6 April 2018]. A classification of the bird species of South America. American Ornithologists' Union. http://www.museum.lsu.edu/~Remsen/SACCBaseline.htm