North American species (Bonasa umbellus) of grouse, sometimes incorrectly called a partridge. Ruffed grouse live mainly on berries, fruits, seeds, and buds but also eat much animal food. They are 16–20 in. (40–50 cm) long and have feathered lower legs and a black band on the fan-shaped tail. The male's ruff consists of erectile black feathers on the sides of the neck. Males beat their wings rapidly against the air (called drumming) to proclaim their territory.