Aythya

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Aythya is a genus of diving ducks, with twelve species currently accepted.<ref name=ioc>Template:Cite web</ref> The genus was described in 1822 by the German zoologist Friedrich Boie, with the type species being greater scaup.<ref>Template:Cite book</ref><ref>Template:Cite book</ref> The name Aythya comes from the Ancient Greek word Template:Lang (Template:Transliteration), which referred to an unknown diving-bird.<ref>Template:Cite book</ref><ref>Template:Cite web</ref>

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.<ref name=hbw>Template:Cite book</ref><ref name=Collins>Svensson, L., Mullarney, K., & Zetterström, D. (2022) Collins Bird Guide, ed. 3. Template:ISBN, pages 30-35</ref>

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.<ref name=hbw/>

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.<ref name=ioc/>

Male	Female	Scientific name	Common name	Distribution	Conservation status
		A. valisineria	Canvasback	North America	least concern
		A. ferina	Common pochard	Northern Europe into Asia	vulnerable
File:Redhead - Aythya americana, Oakley Street, Cambridge, Maryland.jpg	File:Redhead female RWD2.jpg	A. americana	Redhead	North America, from northern Canada to the lower United States	least concern
File:AythyaCollaris 4951.JPG	File:AythyaCollaris 4953.JPG	A. collaris	Ring-necked duck	North America, from Alaska and northern Canada to the central United States, wintering south to the Caribbean; occasional visitor to Western Europe	least concern
File:Hardhead male drip.jpg	Error creating thumbnail:	A. australis	Hardhead	Australia; occasional visitor to New Guinea, New Zealand, and Vanuatu in the Pacific	least concern
File:Aythya baeri, Ukima Pond, Tokyo, Japan 1a.jpg	File:Aythya baeri female.jpg	A. baeri	Baer's pochard	Southeastern Russia and northeastern China, migrating in winter to southern China, Vietnam, Japan, and India	critically endangered
File:Ferruginous Duck by Tisha Mukherjee 08.jpg	File:Ferruginous Pochard (Aythya nyroca) (49177728373).jpg	A. nyroca	Ferruginous duck	From the Iberian Peninsula and the Maghreb east to western Mongolia, south to Arabia	near threatened
File:Madagascar Pochard, Captive Breeding Program, Madagascar 2.jpg	File:Madagascar Pochard, Captive Breeding Program, Madagascar 1.jpg	A. innotata	Madagascar pochard	Madagascar	critically endangered
Error creating thumbnail:	File:New Zealand Scaup (female) with chicks.jpg	A. novaeseelandiae	New Zealand scaup	New Zealand	least concern
File:Male tufted duck (Aythya fuligula) 01.jpg	File:Aythya fuligula (female) 01.jpg	A. fuligula	Tufted duck	Throughout temperate and northern Eurasia; occasional visitor to the United States and Canada	least concern
File:2017-03-24 Aythya marila, male, Killingworth Lake, Northumberland 22.jpg	File:2014-04-14 Aythya marila, female, Killingworth Lake, Northumberland 04.jpg	A. marila	Greater scaup	Iceland, Northern Europe, Northern Asia except the Far East (A. m. marila); far northeastern Asia, Alaska, northern Canada (A. m. nearctica)	least concern
File:Lesser Scaup (6974701193).jpg	File:Aythya affinis.JPG	A. affinis	Lesser scaup	Alaska through western Canada to western Montana, wintering east to the Atlantic Coast and south to Central America; occasional visitor to Western Europe	least concern

Hybrids

File:2014-04-23 Aythya ferina × Aythya fuligula hybrid, Northumberland 2.jpg

A tufted duck × common pochard hybrid. Note the casual resemblance to a lesser scaup in head shape, but distinguishable by the more uniform (less vermiculated) mantle feathers, and the bill pattern with a pale band and large black tip (uniform bluish in lesser scaup).

The species in the genus are all closely related, and are more prone to hybridisation than most other bird genera.<ref name=Collins/><ref name="Lehmhus">Template:Cite journal</ref> Hybrids regularly seen in Europe include tufted duck × common pochard, tufted duck × ring-necked duck, greater scaup × tufted duck, and common pochard × ferruginous duck;<ref name=Collins/> while in North America, ring-necked duck × greater scaup, greater scaup × tufted duck, and canvasback × redhead are frequent.<ref name=Sibley>Template:Cite book</ref> 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.<ref name=Collins/> Usually only male hybrids are evident; female hybrids are less obvious and even more difficult to identify.<ref name=Collins/><ref name=Sibley/>

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.<ref name=hbw/><ref name=bwp>Template:Cite book</ref>

Breeding

The nests are hidden in dense waterside vegetation, for preference on islets which give greater security from land predators. Incubation of the [2–]6–10[–18] eggs 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.<ref name=hbw/><ref name=bwp/> 'Dump nesting', where more than one female lays eggs in a nest, is common, and likely accounts for nests containing more than ten eggs.<ref name=bwp/>

Prehistory

Aythya shihuibas was described from the Late Miocene of China, but probably belongs outside crown group Aythya.<ref>Template:Cite journal</ref> Zelenkov (2016) transferred the species Anas denesi Kessler (2013), known from the late Miocene of Hungary, to the genus Aythya.<ref>Template:Cite journal</ref> An undescribed prehistoric species is known only from Early Pleistocene fossil remains found at Dursunlu, Turkey;<ref>Louchart, Antoine; Mourer-Chauviré, Cécile; Guleç, Erksin; Howell, Francis Clark & White, Tim D. (1998): L'avifaune de Dursunlu, Turquie, Pléistocène inférieur: climat, environnement et biogéographie. C. R. Acad. Sci. Paris IIA 327(5): 341–346. [French with English abridged version] Template:Doi (HTML abstract) </ref> 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.<ref name = Hume>Template:Cite journal</ref>

The Miocene "Aythya" arvernensis is now placed in Mionetta,Template:Verify source while "Aythya" chauvirae seems to contain the remains of two species, at least one of which does not seem to be a diving duck.<ref>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. Template:Doi (HTML abstract) </ref>