Editing Grouse (section)

==Feeding and habits==
Grouse feed mainly on vegetation—buds, [[catkin]]s, 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 [[invertebrate]]s, 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 [[vertebrate]]s refuse. To digest vegetable food, grouse have big [[crop (anatomy)|crops]] and [[gizzard]]s, eat grit to break up food, and have long [[intestine]]s with well-developed [[caecum|caeca]] in which [[symbiosis|symbiotic]] bacteria digest [[cellulose]].<ref name=Firefly/>

[[Forest]] species flock only in autumn and winter, though individuals tolerate each other when they meet. [[Prairie]] species are more social, and [[tundra]] species (ptarmigans, ''[[Lagopus]]'') 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.<ref name=Firefly/>

Most species stay within their breeding range all year, but make short seasonal movements; many individuals of the [[rock ptarmigan|ptarmigan]] (called rock ptarmigan in the US) and [[willow grouse]] (called willow ptarmigan in the US) [[bird migration|migrate]] hundreds of kilometers.<ref name=Firefly/>