Rock ptarmigan

Etymology

The ptarmigan's genus name, Lagopus, is derived from Ancient Greek lagos (λαγώς lagṓs), meaning "hare", + pous (πούς poús), "foot", in reference to the bird's feathered legs.

The species name, muta, comes from New Latin and means "mute", referring to the simple croaking song of the male. It was for a long time misspelt mutus, in the erroneous belief that the ending of Lagopus denotes masculine gender. However, as the Ancient Greek term λαγώπους lagṓpous is of feminine gender, and the species name has to agree with that, the feminine muta is correct.

The word ptarmigan comes from the Scottish Gaelic tàrmachan, literally croaker. The silent initial p was added in 1684 by Robert Sibbald through the influence of Greek, especially pteron (πτερόν pterón), "wing", "feather", or "pinion".

Description

The rock ptarmigan is 34–36 cm (13–14 in) long (tail 8 cm (3.1 in)) with a wingspan of 54–60 cm (21–24 in). It is smaller than the willow ptarmigan by about ten percent. The male's "song" is a loud croaking.

The rock ptarmigan is seasonally camouflaged; its feathers moult from white in winter to brown in spring or summer. The breeding male has greyish upper parts with white wings and under parts. In winter, its plumage becomes completely white except for the black tail. It can be distinguished from the winter willow ptarmigan by habitat—the rock ptarmigan prefers higher elevations and more barren habitat; it is also smaller with a more delicate bill.

Distribution and habitat

The rock ptarmigan is a sedentary species which breeds across arctic and subarctic Eurasia and North America (including Greenland) on rocky mountainsides and tundra. It is widespread in the Arctic Cordillera and is found in isolated populations in the mountains of Norway, Scotland, the Pyrenees, the Alps, Bulgaria, the Urals, the Pamir Mountains, the Altay Mountains, and Japan—where it occurs only in the Japan Alps and on Hakusan mountain. Because of the remote habitat in which it lives, it has only a few predators—such as golden eagles—and it can be surprisingly approachable. It has been introduced to New Zealand, South Georgia, the Kerguelen Islands, and the Crozet Islands.

The small population living on Franz Josef Land in the Russian High Arctic overwinters during the polar night and survives by feeding on rich vegetation on and underneath high cliffs where seabird colonies are located in summer.

During the last ice age, the species was far more widespread in continental Europe.

Feeding

The rock ptarmigan feeds primarily on birch and willow buds and catkins when available. It also eats various seeds, leaves, flowers, and berries of other plant species. Insects are eaten by the developing young.

Breeding

Apart from the comb, the male rock ptarmigan has no ornaments or displays that are typical for grouses in temperate regions. Studies on other grouses have shown that much variation in comb size and colour exists between the species, and that the comb is used in courtship display and aggressive interactions between males. Many studies have shown that there is a strong correlation between the comb size and the level of testosterone in males; one report from 1981 showed that the amount of testosterone is correlated to aggressiveness against other males.

The male's comb has been the focus of studies regarding sexual selection. Studies of a population of male rock ptarmigans in Scarpa Lake, Nunavut, have shown that during the first year, mating success among males was influenced by comb size and condition, and bigamous males had larger combs than monogamous males. The correlation to size disappeared after the first year, but the correlation to comb condition remained. This is consistent with another study of the same population of L. muta that showed that mating success overall is correlated to comb condition. Exceptions were first-time breeders, in which the size of the comb influenced mating success.

The rock ptarmigan becomes sexually mature at six months of age and commonly has up to six chicks. Because of this high breeding rate, the size of the population is affected very little by factors such as hunting.