Grouse are a group of birds. Grouse inhabit temperate and subarctic regions of the Northern Hemisphere, from pine forests to moorland and mountainside.
Grouse are heavily built, like chickens. Males are larger than females—twice as heavy in the western capercaillie, the largest member of the family. Grouse have feathered nostrils. Their legs covered in feathers down to the toes, and in winter the toes, too, have feathers or small scales on the sides, an adaptation for walking on snow and burrowing into it for shelter.
These birds feed mainly on vegetation—buds, catkins, leaves, and twigs—which typically accounts for over 95% of adults' food by weight. Thus, their diets vary greatly with the seasons. Hatchlings eat mostly insects and other invertebrates, gradually reducing their proportion of animal food to adult levels. Several of the forest-living species are notable for eating large quantities of conifer needles, which most other vertebrates refuse. To digest vegetable food, grouse have big crops and gizzards, eat grit to break up food, and have long intestines with well-developed caeca in which symbiotic bacteria digest cellulose.
Forest species flock only in autumn and winter, though individuals tolerate each other when they meet. Prairie species are more social, and tundra species are the most social, forming flocks of up to 100 in winter. All grouse spend most of their time on the ground, though when alarmed, they may take off in a flurry and go into a long glide.
Most species stay within their breeding range all year, but make short seasonal movements; many individuals of the ptarmigan and willow grouse migrate hundreds of kilometers.
In all but one species, males are polygamous. Many species have elaborate courtship displays on the ground at dawn and dusk. The displays feature males' brightly colored combs and in some species, brightly colored inflatable sacs on the sides of their necks. The males display their plumage, give vocalizations that vary widely between species, and may engage in other activities, such as drumming or fluttering their wings, rattling their tails, and making display flights. Occasionally, males fight.

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