The Snow Bunting (Plectrophenax nivalis), sometimes colloquially called "snowflake", is a passerine bird in the bunting family Emberizidae. 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.

The breeding habitat is on tundra, treeless moors, and bare mountains. It is migratory, wintering a short distance further south in open habitats in northern temperate areas, typically on either sandy coasts, steppes, prairies, or low mountains, more rarely on farmland stubble. In winter, it forms mobile flocks.

It is fairly large and long-winged for a bunting, 15-18 cm long and with a wingspan of 32"?38 cm, and weighing 26"?50 g. In flight, it is easily identified by its large white wing patches. The breeding male is unmistakable, with all white plumage and a black back; the breeding female is grey-black where the male is solid black. In winter plumage, both sexes are mottled pale ginger, blackish and white above, and pale ginger and white below, with the males having more white than the females. The bill is yellow with a black tip, all black in summer males. 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.

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

It builds its bulky nest in rock crevices. The eggs are blue-green, spotted brown, and hatch in 12"?13 days, and the young are already ready to fly after a further 12"?14 days.

There are four subspecies, which differ slightly in the plumage pattern of breeding males:

• Plectrophenax nivalis nivalis. Arctic Europe, Arctic North America. Head white, rump mostly black with a small area of white.
• Plectrophenax nivalis insulae. Iceland, Faroe Islands, Scotland. Head white with a blackish collar, rump black.
• Plectrophenax nivalis vlasowae. Arctic Asia. Head white, rump mostly white.
• Plectrophenax nivalis townsendi. 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, and they have been considered conspecific by some authors, though are generally treated separate species.

The species is not endangered at present, with good populations. It shows little fear of humans, and often nests around buildings in Arctic areas, readily feeding on grain or other scraps put out for it.

During the last ice age, the Snow Bunting was widespread throughout continental Europe.