One of our original #BeakoftheWeek stars, the pink-eared duck is the focus of todays blog.
The pink-eared duck is endemic to Australia and is the only member of the genus Malacorhynchus (meaning ‘soft-beak’) alive today. An extinct species of the genus, the Scarlett’s duck (Malacorhynchys scarletti), has been described from New Zealand (Olson, 1977). It is a rather attractive duck, with striking dark brown and white feathers along its chest and flanks, giving it its alternative name the zebra duck. It has buff-brown feathers underneath its tail, brown wings and back, a white rump, white neck feathers, a white face with grey along the forehead and crown and a dark brown patch surrounding a narrow ring of white feathers around the eye.
As its name suggests, the pink-eared duck also has a small pink patch of feathers behind the eye. This patch of feathers is unusual as it contains carotenoid pigments which are absent from the rest of the order Anseriformes (Thomas et al. 2014). Males and females are almost indistinguishable, with females being slightly smaller than males. Juveniles are duller and browner than the adults.
The large, grey bill of the pink-eared duck has a square tip, soft membranous flaps and spatula-like shape. The highly specialised bill also contains rows of fine, comb-like structures called lamellae. These features make the bill perfectly adapted for sweeping through, and filtering, water and mud for the small crustaceans, insects, algae and seeds on which the bird feeds. Individuals may feed alone, in pairs or in groups (See a video of pink-eared ducks feeding here). When foraging, pink-eared ducks are mostly surface filterers, but have been recorded dabbling, up-ending and vortexing. Vortexing disturbs aquatic organisms as the birds rotate, meaning both individuals benefit from this behaviour.
Pink-eared ducks have a variety of calls, including trilling, twittering, chirruping and a low ‘grunk’ sound.
Breeding pairs are thought to be monogamous and these ducks probably have a long-lasting pair bond. Nests are built in tree hollows, nest boxes or the old-nests of other water birds. The female lays a clutch of 3-11 creamy white eggs and incubates them for around 26 days. The ducklings are covered in brown and white down, with a distinctive brown eyestripe. Their bills already have the membranous flaps of the adult birds. Both adults tend the offspring, and fledging occurs when the ducklings are 45-60 days old.
The pink-eared duck is highly mobile and can be found in temporary, saline or brackish waters, or more permanent waterbodies across inland Australia. Because of its nomadic nature, population size is hard to estimate, but is thought to fall between a few hundred thousand to over one million individuals. The IUCN list the pink-eared duck as least concern. Hunters may shoot a large number of these birds, but only across parts of its range.
Adams, L. 2013. Scarlett’s duck. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz
BirdLife International (2012). Malacorhynchus membranaceus. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 02 July 2015.
BirdLife International (2015). Species factsheet:Malacorhynchus membranaceus. Downloaded fromhttp://www.birdlife.org on 02/07/2015.
Carboneras, C. & Kirwan, G.M. (2014). Pink-eared Duck (Malacorhynchus membranaceus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.) (2014). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/52897 on 2 July 2015).
Griffin, P. 2013. Pink-eared duck. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz
Olson, S.L. (1977). Notes on subfossil Anatidae from New Zealand, including a new species of Pink-eared Duck Malacorhynchus. Emu, 77: 132-135.
Thomas, D.B., McGraw, K.J., Butler, M.W., Carrano, M.T., Madden, O. & James, H.F. (2014). Ancient origins and multiple appearances of carotenoid-pigmented feathers in birds. Proc. R. Soc. B, 281: 20140806. DOI: 10.1098/rspb.2014.0806