The Collaborative International Dictionary
Snowbird \Snow"bird\, n. (Zo["o]l.)
An arctic finch ( Plectrophenax nivalis syn. Plectrophanes nivalis) common, in winter, both in Europe and the United States, and often appearing in large flocks during snowstorms. It is partially white, but variously marked with chestnut and brown. Called also snow bunting, snowflake, snowfleck, and snowflight.
Any finch of the genus Junco which appears in flocks in winter time, especially Junco hyemalis in the Eastern United States; -- called also blue snowbird. See Junco.
The fieldfare. [Prov. Eng.]
Wiktionary
n. A finch, (taxlink Plectrophenax nivalis species noshow=1), having white plumage; it is widely distributed in northern latitudes.
WordNet
Wikipedia
The snow bunting (Plectrophenax nivalis), sometimes colloquially called a snowflake, is a passerine bird in the Calcariidae family . 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, and also Cape Breton Highlands. The snow bunting is the most northerly recorded passerine in the world.