perdiz de nieve

La perdiz nival ( Lerwa lerwa ) es un ave de caza de la familia Phasianidae , ampliamente distribuida en las regiones de gran altitud del Himalaya , en Pakistán , China , India y Nepal . Es la única especie de su género y se considera el miembro más basal del clado eréctil de la subfamilia Phasianinae . Habita en pastizales alpinos y laderas abiertas por encima del límite arbóreo , pero no en terrenos rocosos tan áridos como el gallo nival del Himalaya , y no es tan esquiva como esta última. Machos y hembras tienen un plumaje similar, pero los machos presentan un espolón en el tarso .

Esta perdiz parece gris arriba y castaña abajo con pico y patas de color rojo brillante y las partes superiores finamente barradas en blanco y negro. En vuelo, el patrón de primarias y secundarias de color marrón oscuro con un estrecho margen blanco posterior las hace algo parecidas al mucho más grande gallo nival tibetano . La cola de 14 plumas es oscura y barrada en blanco. Hay variación en el tono y algunas aves tienen una corona casi negra. ^{[ 3 ]} Las primarias y secundarias son marrones y el pecho es castaño oscuro. El abdomen tiene más blanco y los flancos inferiores y las plumas alrededor de la cloaca están barradas en marrón y blanco. Las coberteras infracaudales son castañas con estrías negras en el raquis y puntas blancas. Las aves jóvenes tienen las partes inferiores moteadas y el barrado menos definido. El tarso está emplumado en la parte delantera de la pata hasta la mitad de los dedos. ^{[ 4 ] [ 5 ] [ 6 ]}

Mide entre 38 y 40  cm de longitud. Las hembras pesan entre 450 y 580 g; los machos, entre 550 y 700 g. Ambos sexos presentan un plumaje similar: la hembra carece de espolones en el tarso, mientras que el macho tiene un espolón romo y, a veces, un segundo espolón incipiente. Los polluelos plumosos se asemejan a los del faisán sangriento . ^{[ 7 ]} Los polluelos nacen con los tarsos emplumados y la abertura nasal cubierta de plumas. ^{[ 8 ]}

This species was first described by Brian Houghton Hodgson in 1833 and given the genus name Lerwa based on the Bhutia name for it in Nepal.^[9][10] Hodgson initially placed it in the genus Perdix calling it Perdix lerwa.^[11] A subspecies, L. l. major was described by Richard Meinertzhagen from Sichuan while L. l. callipygia from south Kansu was noted by Stegmann in 1938, but these are not usually recognized.^[12][13][14] The species has been retained in this monotypic genus due to various peculiarities including the tarsus feathering and the lack of clear sexual dimorphism in plumage.^[7] A species of bird louse, Chelopistes lervicola has been described as an ectoparasite of this species, and other species in this louse genus are known to parasitize the Cracidae, Meleagrididae and Odontophorinae of the New World.^[15]

Snow partridge is found in the Himalayas from Pakistan to Arunachal Pradesh along the higher ranges, mainly 3000 to 5000 m (rarely below 2000 m) altitude. It is found above the tree line but not on as bare and stony terrain as the snowcocks.^[12] Although said to be found in Afghanistan, there is no evidence.^[3] The species is found over a large area is generally considered to be of low conservation concern. It is hunted to some extent, due to its habit of being more approachable than snowcock and has declined in population in some areas.^[7]

The usual habitat is alpine pastures, open grassy hillsides with grass, lichens, moss, ferns and rhododendrons. Is found among small snow-patches but not in as stony or bare ground as the snowcock. The birds however are very local in their distribution.^[3][7][8]

The snow partridge is found is small groups, usually about 6 to 8 but up to 30 during the non-breeding season. When flushed, they usually fly up before scattering away with noisy wing beats. The flight is rapid and stirring. It has a habit of sunning itself on rocks during the midday.^[3] The call in the breeding season is said to resemble that of the grey francolin of the plains.^[7] It has been compared in habit to that of the ptarmigan. It is said to feed on mosses, lichens, berries, and the shoots of plants. It also swallows grit to aid digestion.^[10][16][17]

The breeding season is May to July. The males are believed to be monogynous. The nest is a scrape on a hill-side under some sheltering rock, either scratched out by themselves or already available, and usually hidden with vegetation.^[10] The nest is sometimes lined with moss but well concealed although given away by the male. About 3 to 5 eggs, pale yellow in color and slightly glossy with reddish-brown markings on the rounded end,^[10] are laid, and the female incubates while the male stands sentinel. Parent birds may use distraction displays to draw the attention of predators. They call in a comparatively softer lower note to the young, which respond with chicken-like cheep calls.^{[18][19][20][21]}

Apart from Chelopistes lervicola described as an ectoparasite of this species, an Argasid tick Argas himalayensis has been noted.^[22][23]

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