Snow bunting

The snow bunting (''Plectrophenax nivalis'') is a passerine bird in the family Calcariidae. It is an Arctic specialist, with a circumpolar Arctic breeding range throughout the northern hemisphere. There are small isolated populations on a few high mountain tops south of the Arctic region, including the Cairngorms in central Scotland and the Saint Elias Mountains on the southern Alaska-Yukon border, as well as the Cape Breton Highlands. The snow bunting is the most northerly recorded passerine in the world.

Taxonomy

The snow bunting was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his '' Systema Naturae''. He placed it with the buntings in the genus ''Emberiza'' and coined the binomial name ''Emberiza nivalis''. He specified the locality as Lapland. It is now placed in the genus '' Plectrophenax'' that was introduced in 1882 by the Norwegian born zoologist Leonhard Stejneger with the snow bunting as the type species. The genus name ''Plectrophenax'' is from Ancient Greek ''plektron'', "cock’s spur", and ''phenax'' "imposter", and the specific ''nivalis'' is Latin for "snow-white".

The snow bunting was formerly classified in the family Emberizidae, which included American sparrows, buntings, towhees and finches. All these species came into existence after a broad geologically recent radiation of passerine birds. However, it is now part of the narrower family Calcariidae, which also contains the longspurs. Despite the wide distribution of this species there are only very small differences between different phenotypes.

Four subspecies are recognised, which differ slightly in the plumage pattern of breeding males:Byers, C., Olsson, U., & Curson, J. (1995). ''Buntings and Sparrows''. Pica Press .
*''P. n. nivalis'' (Linnaeus, 1758) – Arctic Europe, Arctic North America. Head white, rump mostly black with a small area of white.
*''P. n. insulae'' Salomonsen, 1931 – Iceland, Faroe Islands, Scotland. Head white with a blackish collar, rump black.
*''P. n. vlasowae'' Portenko, 1937 – Arctic Asia. Head white, rump mostly white.
*''P. n. townsendi'' Ridgway, 1887 – Aleutian Islands, Kamchatka, coastal far eastern Siberia. As ''vlasowae'', but slightly larger.

It is very closely related to the Beringian McKay's bunting, which differs in having even more white in the plumage. Hybrids between the two occur in Alaska,Sibley, D. (2000). ''The Sibley Guide to Birds''. National Audubon Society and they have been considered conspecific by some authors, though they are generally treated as separate species. American Ornithologists' Union: ''Checklist of North American Birds''.

The species also mated with a Lapland Longspur creating a hybrid. The first photographs of this hybrid were taken in April 2011, during its spring migration.

Description

The snow bunting is a sexually dimorphic, medium-sized passerine bird. This passerine is a ground-dwelling species that walks, runs and could potentially jump if needed. It is fairly large and long-winged for a bunting. It measures 15 cm with a wingspan of and weights 30 to 40 grams. The bill is yellow with a black tip, and is all black in summer for males. The plumage is white in the underparts and the wings and back have black and white on them. The female and male have a different plumage. During the breeding season, the male is white with black wingtips and a black back, while the female has black wingtips and a rufous back. During the winter, they will both have a rufous colouration in the back. In the spring, the buntings will not go through a moult as other passerines do, instead the breeding colouration comes with the wearing and abrasion of the feathers. Unlike most passerines, it has feathered tarsi, an adaptation to its harsh environment. No other passerine can winter as far north as this species apart from the common raven.

This species is often confused with McKay's bunting (''Plectrophenax hyperboreus'') due to the similar colouration of their plumage. Even more, the challenge of identification becomes harder when these two species hybridize at the boundaries of their territories. Another similar species is the horned lark, although it has a larger black tail and it has a smaller white patch on the wings.

Vocalizations

The call is a distinctive rippling whistle, ''per,r,r,rit'' and the typical ''Plectrophenax'' warble ''hudidi feet feet feew hudidi''.

Snow buntings use vocalizations to communicate among each other and males will have a song to attract the female. The communication calls are done by both the male and the female and they tend to be emitted in flight or in the ground, while the males will often emit the song from a perching position or in a flight display. The males will start singing as soon as they will reach the breeding grounds, and will stop once they find a mate. Studies have shown that the quality and the rate at which a song is emitted affect the reproductive success of a male. The rate of a song measured by the number of strophes per minute is limited by the foraging needs of the male; therefore, a male that is able to sing more frequently shows that he is more successful and effective in his foraging behavior. The song becomes an indicator of the parental care qualities of the male, since having an effective foraging behavior will provide a better probability of survival of the nestlings. Females will then choose their mates based on their song rate.
Within snow buntings, vocalizations in males are unique to each individual, although there is certain syllable sharing between one another. The uniqueness of each song reveals a capacity of recognition between individuals and has an effect in the individual fitness and reproductive success. The songs have duration of 2 seconds and have a frequency of 2 to 6 kHz. Each song is composed of similar and dissimilar figures that create different motifs that will alternate and repeat, resulting in a unique pattern for every male individual.

Distribution and habitat

The snow bunting lives in very high latitudes in the Arctic tundra. There is no apparent limit to its northern range, while the southern range is limited by the duration of daylight, which influences their reproductive activity. This species is found in the high Arctic tundra of North America, Ellesmere Island, Iceland, higher mountains of Scotland, Norway, Russia, North Greenland, Siberia, Novaya Zemlya, and Franz Josef Land. During the winter, this bird migrates to the circumglobal northern temperate zone including the south of Canada, north of the United States, north of Germany, Poland, Ukraine, and east to central Asia. During the last ice age, the snow bunting was widespread throughout continental Europe.


During the breeding period the snow bunting looks for rocky habitats in the Arctic. Since the vegetation in the tundra is low growing, this bird and its nestlings are exposed to predators, and in order to ensure the survival of its offspring, the snow bunting nests in cavities in order to protect the nestlings from any threat. During this period, buntings also look for a habitat rich in vegetation such as wet sedge meadows and areas rich in dryas and lichens. In the winter, they seek open habitats such as farms, barren fields, and lakeshores, where they feed on seeds in the ground.

Migration

The snow buntings migrate to the Arctic to breed and they are the first migrant species that arrives in these territories. They must gain at least 30% of body mass before migration. The males will arrive first at the beginning of April, when the temperature could reach −30 degrees Celsius. This early migration could be explained by the fact that this species is highly territorial and the quality of the nesting area is crucial to their reproductive success. Females will arrive four to six weeks later, when the snow starts to melt. They tend to migrate in small flocks and have an undulating flight at a moderate height.

The birds overwinter in northern temperate zones in open fields and forms moving flocks that can number into the hundreds. They will leave the Arctic at the middle and end of September, although some will start the migration at the beginning of November. The female leaves first and tends to winter in more southern territories than the male, while the juveniles will leave the Arctic even later than the adults.

The migration is nocturnal and the birds are able to detect the geomagnetic field of the earth in order to guide themselves to their breeding and overwinter territory. The orientation of the snow bunting during migration is independent of any type of visual cue. Furthermore, studies have shown that only those individuals with adequate energy storage will be able to select seasonally appropriate directions during their migration.

Behaviour

Food and feeding

From the fall to the spring the snow bunting eats a variety of weeds such as knotweed, ragweed

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