Horned grebe

The horned grebe or Slavonian grebe (Podiceps auritus) is a relatively small and threatened species of waterbird in the family Podicipedidae. There are two subspecies, P. a. auritus (Slavonian grebe), which breeds in Eurasia, and P. a. cornutus (horned grebe), which breeds in North America. The Eurasian subspecies is distributed over most of northern Europe and northern Asia, breeding from Iceland east to the Russian Far East. The North American subspecies spans most of Canada and some of the United States. A small population was cited in Greenland in 1973, but is not mapped or further mentioned by subsequent authors.

The American name 'horned' refers to the orange-yellow crest feathers located above and behind the eyes, called "horns". The English name, originally 'Sclavonian', is first attested by George Montagu in his 1802 Ornithological Dictionary, from Sclavonia, an old name for northern Prussia, referring to the species' main breeding area in Europe; the spelling was emended (without any reason given) to the current 'Slavonian' by Hartert in 1912.

The species can be recognised by its orange-red and black breeding plumage, its black and white non-breeding plumage, and its characteristic "horns". It is 31–38 cm (12–15 in) long, has a wingspan 55–74 cm (22–29 in) wide and weighs 300–570 g (11–20 oz). It has a moderately long neck, flat forehead and a rear crown of black feathers. Its beak is straight and pointed, with a white tip.

The breeding plumage has bright erectable "horns", black fan-shaped cheek feathers and an overall red-and-black colour. The neck, flanks, lores and upper-chest are chestnut brown, while the crown and back are black. The belly is a dull white. Males are slightly larger and brighter than females but are generally indistinguishable.

The non-breeding plumage is overall black and white. The neck, chest and cheeks are white, while the back and crown are a dull black-grey. The border between the crown and the cheeks extend in a straight line behind the eyes. The winter plumage does not have the "horns".

Juveniles appear similar to a non-breeding adult except they are a slightly duller shade of white and their back is tinged with brown. The line separating the cheeks and crown is less distinct and their beak is paler. The chicks are fluffy, with a dull grey back, a white belly and distinct black-and-white facial and neck striping.

Two subspecies are accepted:

The subspecies are physically similar in measurements, but differ subtly in plumage, with P. a. auritus darker, having a blacker back and crown, and orange-yellow lateral crown tufts in breeding plumage; and P. a. cornuta paler, with greyer back and crown, and straw-yellow tufts.

A third subspecies P. a. arcticus Boie, 1822 has sometimes been accepted for the population in coastal Norway, Iceland, and Scotland, but is now treated as synonymous with nominate P. a. auritus.

In winter plumage, it is often confused with the black-necked grebe, which is only slightly smaller in size and has similar colouring but is differentiated by a steeper forehead, a more slender, slightly uptilted bill, duskier cheeks, and a fluffier rump.

Young begin calling for begging purposes in a slightly trilled peeping noise, similar to that of a domestic chick. As they mature, their song changes to a more adult-like chittering. Their typical advertising call is loud and nasally "aaarrh" descending in a pitch and ending in a trill. They use other calls during copulation, alarm and breeding ceremonies that are slightly variable from the advertising call. Horned grebes are extremely vocal during breeding, territory establishment and defence. Their song is subdued during autumn migration and at wintering sites.