willow ptarmigan

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A ptarmigan (Lagopus lagopus) of Arctic regions, having brownish plumage that turns white in winter.

from The Century Dictionary.

• noun The common ptarmigan of North America, Lagopus albus, having in winter white plumage with a black tail, but no black stripe through the eye: distinguished from rock-ptarmigan. Also willow-grouse. The name originally applied to the European bird named L. saliceti. See dalripa and ryper.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A willow grouse, Lagopus lagopus.