Chiloe Wigeon Mareca sibilatrix Scientific name definitions

A fairly common, range-restricted duck of southern South America, the Chiloe Wigeon is most likely to be found on lakes, lagoons, slow-flowing rivers and other bodies of freshwater.  The Chiloe Wigeon is generally a sedentary species; however, the individuals that breed in the southern most portions of South America do exhibit short-range migratory patterns to central South America. Like other dabbling ducks, the Chiloe Wigeon feeds on aquatic vegetation from the surface of the water by head-dipping and upending; it also will graze from land. Despite having a small global range, the Chiloe Wigeon is not threatened and is generally common throughout its range.

43–54 cm; 720–1085 g (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close , 2 Pagano, L. G., and S. A. Salvador (2017). Datos de pesos de aves Argentinas. Parte 4. Historia Natural 7:21–43. Close ). Compact, heavier than other wigeons, with only slight sexual dimorphism. Flank colour variable. Male has no eclipse plumage: forehead and face  white with small whitish patch behind and below eye, black head and neck with broad iridescent green band from eye to nape, mantle, scapulars and tertials black fringed white or buff, median and greater wing-coverts white, secondaries velvet black lined with white on outer edge, primaries and tail mid brown to black, with white upper- and lower tail-coverts; breast white barred black, sometimes with some rust colour near belly  , which is also white, mottled rusty chestnut at sides , sometimes more or less solidly; bill slate-blue with black nail and mandible, legs silver grey and eyes brown. Female somewhat duller , with less green on head, with less white on face  , and white of wing-coverts and rump, and black of secondaries mottled or dusky. Juvenile duller with little iridescence on head and has barred flanks, while young female has white of coverts tinged dingy or barred brown, and secondaries are more grey than black.

• Eurasian x Chiloe Wigeon (hybrid) Mareca penelope x sibilatrix

South America S of C Argentina and C Chile; Falkland Is. Winters to S Paraguay and SE Brazil.

Shallow freshwater lakes, marshes, lagoons and slow-flowing streams or rivers surrounded by scattered trees not far from grassland and meadows, but also occasionally visits coastal shorelines to feed (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Waterbodies with dense submergents such as Potamogeton, Ruppia, Nitella, Lileopsis and Zanichella, or floating carpets of Myriohyllum, are especially favoured (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ).

Southernmost breeding populations move to lower latitudes in winter, as far N as Uruguay and S Brazil  (Rio Grande do Sul, where recorded in Jan–Feb, Jun–Aug and Oct) (3 Maurício, G.N. and Dias, R.A. (1996). Novos registros e extensões de distribuição de aves palustres e costeiras no litoral sul do Rio Grande do Sul. Ararajuba. 4(1): 47–51. Close ), with an exceptional, undocumented record of vagrancy from C Peru (Junín) (4 Fjeldså, J., and N. Krabbe (1990). Birds of the High Andes: A Manual to the Birds of the Temperate Zone of the Andes and Patagonia, South America. Zoological Museum, University of Copenhagen and Apollo Books, Copenhagen and Svendborg, Denmark. Close ); sedentary in Falkland Is. Has occurred on South Georgia (six records between 1972 and 1985) (5 Prince, P. A., and J. P. Croxall (1996). The birds of South Georgia. Bulletin of the British Ornithologists’ Club 116(2):81–104. Close ), South Shetland Is and South Orkney Is (13 records on the two archipelagos since 1966) (5 Prince, P. A., and J. P. Croxall (1996). The birds of South Georgia. Bulletin of the British Ornithologists’ Club 116(2):81–104. Close ), with a record (in late Sept) 35 km off the coast of Tierra del Fuego, Argentina (6 Seco Pon, J.P. and Bastida, J. (2015). Patos Barcino (Anas flavirostris), Capuchino (Anas versicolor), y Overo (Anas sibilatrix) en el sur del Océano Atlántico. Nuestras Aves. 60: 54–55. Close ).

Essentially vegetarian ; grasses, sedges and greener parts of plants and aquatic vegetation, as well as their seeds, but worms, larvae and small fish also recorded in stomach contents, perhaps especially in summer (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Of 37 stomach contents examined in Chile, composition was 82·9% Potentilla anserina seeds, 5·7% Triglochium montevidense and 3·6% Polygonum avicular, with some grit in the gizzards (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Feeds mainly by grazing on dry land and coastal shorelines, where it grazes kelp (7 Woods, R. W., and A. Woods (1997) Atlas of Breeding Birds of the Falkland Islands. Anthony Nelson, Oswestry, UK. Close ); also by dabbling, head dipping and upending while swimming in open waters. Associates with other ducks such as Lophonetta specularioides and Anas flavirostris (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ).

Very vocal, even at night, with male giving loud, bisyllabic, whistled “rakoo”, which may be preceded by snorts in courtship, when separated from female, post-copulation or during “Triumph Ceremony”, while female utters loud honks during latter display and a rolling “errr” to entice male to copulate, as well as a series of evenly spaced honking notes when nest prospecting (“Persistent Quacks”); both pair-members produce soft chittering calls or honks when foraging or in company of ducklings, while in alarm male employs sharp, rising whistle and female a loud honk, and female has also been heard to give series of two honks on descending pitch when separated from mate (“Decrescendo” call); ducklings utter typical distress and contentment vocalizations, but female develops high-pitched honks and male trills with age (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ).

Starts Aug/Sept, with courtship noted as early as Jul in Argentina and Jun–Jul in Chile; season generally Dec–Feb in Argentina, Oct–Dec in C Chile (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ) and Sept–Dec on Falkland Is (7 Woods, R. W., and A. Woods (1997) Atlas of Breeding Birds of the Falkland Islands. Anthony Nelson, Oswestry, UK. Close ). Monogamous and pair-bonds suspected to be long-term (birds remaining together throughout non-breeding season) (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). In single pairs or loose groups; nests on ground among vegetation, typcially 10–30 m from water (occasionally much further) (7 Woods, R. W., and A. Woods (1997) Atlas of Breeding Birds of the Falkland Islands. Anthony Nelson, Oswestry, UK. Close ), sometimes in lake-fringing reeds, but more usually grass (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Occasionally double-brooded in captivity (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Clutch generally 5–9 ivory-coloured eggs (but larger broods recorded, see below), size 53·8–61 mm × 39·5–42 mm, mass (in captivity) 41–59 g (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ); incubation c. 24–26 days by female alone (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ); chicks have dark brown down above, buffy below, with largely rufous face , large buff or white spots either side of rump, on flanks and scapulars, mean weight 31·2 (day-old captive-bred birds) (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ); fledging period apparently unknown, but both adults care for brood (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Mean brood size on hatching 6·74 in Argentina (range 2–10) or 8·42 in Chile (5–13), with survival to fledging averaging c. 67% in Patagonian Argentina (range 33–100%). Achieves sexual maturity at one year old in captivity (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ).

Not globally threatened (Least Concern). Widely distributed and fairly common in most of range, with an overall population estimated at 100,000–1,000,000 individuals (1 Kear, J., Editor (2005). Ducks, Geese and Swans. Volume 1: General chapters, and Species accounts (Anhima to Salvadorina). Oxford University Press, Oxford, UK. Close ). Important breeding sites in Argentina include Laguna Blanca, Neuquén Province, with 500 individuals recorded in Jan/Feb census in 1982, and, of particular importance, the Meseta de Strobel, Santa Cruz Province, where an estimated 18,900 individuals were counted recently, although the species has not been proven to breed in this region (8 Lancelotti, J.L., Pozzi, L.M., Márquez, F., Yorio, P. and Pascual, M.A. (2009). Waterbird occurrence and abundance in the Strobel Plateau, Patagonia, Argentina. El Hornero. 24(1): 13–20. Close ). In Falkland Is, widely distributed, nowhere very common but locally numerous, with an estimated 500–900 pairs during the 1983–1993 breeding birds census (7 Woods, R. W., and A. Woods (1997) Atlas of Breeding Birds of the Falkland Islands. Anthony Nelson, Oswestry, UK. Close ). Despite hunting pressure (even on Falkland Is) and habitat loss, population does not appear to have declined significantly. Feral populations may exist in some European countries, e.g. in France (9 Dubois, P.J. (2012). Les populations d’oiseaux allochtones en France en 27811 (2e enquête nationale) Ornithos. 19(4): 225–251. Close ).