a ptarmigan, Lagopus lagopus, of arctic and subarctic regions of the New and Old Worlds, having brown, mottled plumage in summer and white plumage in winter.
Compare red grouse.
Origin of willow ptarmigan
An Americanism dating back to 1870–75
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019