Grouse are a group of birds from the order Galliformes, in the family Phasianidae. Grouse are frequently assigned to the subfamily Tetraoninae (sometimes Tetraonidae), a classification supported by mitochondrial DNA sequence studies, and applied by the American Ornithologists' Union, ITIS, and others. Grouse inhabit temperate and subarctic regions of the northern hemisphere, from pine forests to moorland and mountainside, from 83° North (rock ptarmigan in northern Greenland) to 28° North (Attwater's prairie chicken in Texas).