Aythya

''Aythya'' is a genus of diving ducks, with twelve species currently accepted. The genus was described in 1822 by the German zoologist Friedrich Boie, with the type species being greater scaup. The name ''Aythya'' comes from the Ancient Greek word (), which referred to an unknown diving-bird.

The species are plump, compact, medium-sized ducks ranging from 37–61 cm long, 60–84 cm wingspan, and weighing 410–1600 g, with canvasback the largest, and ring-necked duck and ferruginous duck marginally the smallest. The body plumage is variably white, grey, red-brown, or black, often with a finely vermiculated pattern; in several species, the flanks are white or pale grey, the back darker grey to black, and the breast and tail black. The heads are strongly coloured in the males, orange-red in some species, and black with a green to purple sheen ( structural colour) in good light; the sheen colour varies with both species and angle of light incidence – in for example greater scaup, the head has a green sheen in direct light, but a purple sheen when backlit. In females, the heads are browner, sometimes with white patterning on the face. The eye colour is also variable in males, from white in ferruginous duck (leading to its archaic name of "white-eyed pochard"), through yellow in most species, to deep red in common pochard and canvasback; in females, the eye is brown in all species. The bills are short, fairly broad, and pale blue-grey to black, usually with a small black 'nail' at the tip; the pattern of blue-grey and black is important in species identification. In flight, the wings are dark grey to black, with a white to pale grey wingbar along the primary and secondary feathers; the pattern of the wingbar (whether all-white, or all-grey, or white on the secondaries and grey on the primaries) is an important identification feature. The webbed feet, used for propulsion in both swimming and diving, are 5–7 cm long, large for the size of the birds, and dark grey to blackish in all the species. Svensson, L., Mullarney, K., & Zetterström, D. (2022) '' Collins Bird Guide'', ed. 3. , pages 30-35

The species occur throughout Asia, Europe, North America, Australia, New Zealand, and Madagascar, and also in the northern half of Africa primarily in winter. Small numbers also reach the far north of South America in winter. In the breeding season, they are restricted to well-vegetated freshwater lakes, while in the winter they use both freshwater lakes and sheltered saltwater bays and inlets.

''Aythya'' species

The genus contains 12 species; all are monotypic except for ''A. marila'', which has two subspecies in the Old and New Worlds, respectively.

Hybrids

The species in the genus are all closely related, and are more prone to hybridisation than most other bird genera. Hybrids regularly seen in Europe include tufted duck × common pochard, tufted duck × ring-necked duck, greater scaup × tufted duck, and common pochard × ferruginous duck; while in North America, ring-necked duck × greater scaup, greater scaup × tufted duck, and canvasback × redhead are frequent. These hybrids can often resemble, and be mistaken for, other species in the genus; for example tufted duck × common pochard hybrids are easily mistaken for lesser scaup. Usually only male hybrids are evident; female hybrids are less obvious and even more difficult to identify.

Diet

The diet, mostly obtained by diving to depths of 0.5–6 m (exceptionally 10 m), but also at times from the surface without diving, consists of a mixture of plant material (including seeds, leaves and roots of water plants) and bottom-dwelling invertebrates (including worms, molluscs, insects). In urban situations, several species have learnt to take bread or birdseed fed to ducks by people.

Breeding

The nests are hidden in dense waterside vegetation, for preference on islets which give greater security from land predators. Incubation of the ––10 ��18eggs takes 3–4 weeks, and is done entirely by the female. The ducklings fledge at around 6–7 weeks old, and are cared for primarily by the female, though the male may assist with guarding the ducklings. 'Dump nesting', where more than one female lays eggs in a nest, is common, and likely accounts for nests containing more than ten eggs.

Prehistory

''Aythya shihuibas'' was described from the Late Miocene of China, but probably belongs outside crown group ''Aythya''. Zelenkov (2016) transferred the species '' Anas denesi'' Kessler (2013), known from the late Miocene of Hungary, to the genus ''Aythya''. An undescribed prehistoric species is known only from Early Pleistocene fossil remains found at Dursunlu, Turkey; it might however be referrable to a paleosubspecies of an extant species considering its age (see also Greater scaup). Subfossils have also been found on Réunion; this Réunion pochard awaits formal description, and may prove to have been a population of the Madagascar pochard.

The Miocene ''"Aythya" arvernensis'' is now placed in '' Mionetta,'' while ''"Aythya" chauvirae'' seems to contain the remains of two species, at least one of which does not seem to be a diving duck. Worthy, Trevor; Tennyson, A.J.D.; Jones, C.; McNamara, J.A. & Douglas, B.J. (2007): Miocene waterfowl and other birds from central Otago, New Zealand. '' J. Syst. Palaeontol.'' 5(1): 1–39. (HTML abstract)

See also

* Late Quaternary prehistoric birds
* List of fossil bird genera

Gallery

File:Canvasback pair2.jpg, Canvasback (''Aythya valisineria'')
File:Aythya ferina (Marek Szczepanek).jpg, Common pochard (''Aythya ferina'')
File:Redhead in Central Park (15369).jpg, Redhead (''Aythya americana'')
File:Aythya-collaris-001.jpg, Ring-necked duck (''Aythya collaris'')
File:Aythya australis female - Hurstville Golf Course.jpg, Female Hardhead (''Aythya australis'')
File:Aythya baeri cropped.jpg, Baer's pochard (''Aythya baeri'')
File:Moretta Tabaccata - Ferruginous Duck - Aythya nyroca.jpg, Ferruginous duck (''Aythya nyroca'')
File:AythyaInnotata.svg, Madagascar pochard (''Aythya innotata'')
File:NZ Scaup 01.jpg, New Zealand scaup (''Aythya novaeseelandiae'')
File:Tufted-Duck-male-female.jpg, Tufted duck (''Aythya fuligula'')
File:2017-03-24 Aythya marila, pair, Killingworth Lake, Northumberland 01.jpg, Greater scaup (''Aythya marila'')
File:AythyaAffins 2109.JPG, Lesser scaup (''Aythya affinis'')

References

{{Taxonbar, from=Q214300

Diving ducks
Bird genera
Taxa named by Friedrich Boie