Grouse are a group of birds from the order Galliformes. They are sometimes considered a family Tetraonidae, though the American Ornithologists' Union and many others include grouse as a subfamily Tetraoninae in the family Phasianidae. 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).