Canard à sourcils

Identification

This sociable duck is found in a variety of wetland habitats, and its nesting habits are much like those of the mallard, which is encroaching on its range in New Zealand. It feeds by upending, like other Anas ducks.<p>It has a dark body, and a paler head with a dark crown and facial stripes. In flight, it shows a green speculum and pale underwing. All plumages are similar. The size range is 54–61 cm; males tend to be larger than females, and some island forms are smaller and darker than the main populations. It is not resident on the Marianas islands, but sometimes occurs there during migration. The now-extinct Mariana mallard was probably originally derived from hybrids between this species and the mallard, which came to the islands during migration and settled there.<p>Like its relatives the mallard and American black duck, the Pacific black duck is one of a number of duck species that can quack, with the female producing a sequence of raucous, rapid quacking which decreases in volume.

Taxonomie

The Pacific black duck was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with all the other ducks, geese and swans in the genus Anas and coined the binomial name Anas superciliosa. Gmelin based his description on the "Supercilious duck" that had been described in 1785 by the English ornithologist John Latham in his A General Synopsis of Birds. The naturalist Joseph Banks had provided Latham with a water-colour drawing of the duck by Georg Forster who had accompanied James Cook on his second voyage to the Pacific Ocean. His picture was drawn at Dusky Sound, a fiord on the southwest corner of New Zealand. This picture is the holotype for the species and is now held by the Natural History Museum in London. The genus name Anas is the Latin word for a duck. The specific epithet superciliosa is from Latin meaning "supercilious" or "eye-browed", a reference to the prominent supercilium or eye-stripe.<p>Two subspecies are now recognised:<p>A third subspecies, rogersi from Australia, has sometimes been recognised but it not distinguishable either genetically or phenotypically from the nominate race.

Nom scientifique

Anas superciliosa

Autorité

Gmelin, JF, 1789

Ordre

Ansériformes

Famille

Anatidae

Genre

Anas

Répartition et habitat

Migration

Espèce sédentaire

Comportement

Mode de migration: Espèce sédentaire.

Conservation

Les effectifs du Canard à sourcils ont fortement diminué en Nouvelle-Zélande et sur plusieurs îles australiennes en raison de la concurrence et de l'hybridation avec le Canard colvert introduit. Selon Rhymer et al. (1994), leurs données indiquent que le Canard à sourcils pourrait finir par perdre son identité d'espèce distincte en Nouvelle-Zélande, puis être remplacé par une population d'hybrides comparable à celle du Canard des Mariannes. Des études portant sur ses trois espèces de poux parasites des plumes étayent cette prévision. Le même phénomène touche de nombreuses régions d'Australie, en particulier la Tasmanie et Adélaïde.<p>On supposait que les mâles colverts s'accouplaient avec les femelles de Canard à sourcils beaucoup plus souvent que l'inverse, car la plupart des hybrides présentent un plumage de type colvert. Cette interprétation est toutefois erronée : le phénotype du colvert semble dominant et le plumage ne permet pas de déterminer la contribution de chaque espèce à l'ascendance d'un hybride. Le remplacement du Canard à sourcils paraît surtout lié à la domination physique des colverts, plus grands, conjuguée au déclin marqué du Canard à sourcils causé par la chasse excessive au milieu du XXe siècle.

Tendance de la population

unknown