grouse a name which has a fairly wide application, hither and yonder, to various birds in the family Phasianidae, but which usually refers to the species Lagopus lagopus, in which the most important subspecies are L. l. scoticus, the red grouse of Britain, and L. l. lagopus, the willow grouse (or, in N. America, willow ptarmigan). The word is also part of the names black grouse (Tetrao tetrix, Europe to Siberia); hazel grouse (Bonasa bonasia, Scandinavia and C. Europe to the Orient); and ruffed grouse (Bonasa umbellus, important in N. America). See also capercaillie.