The western capercaillie (Tetrao urogallus), also known as the wood grouse, heather cock, or just capercaillie /ˌkæpərˈkeɪli/, is the largest member of the grouse family. The largest known specimen, recorded in captivity, had a weight of 7.2 kg (16 lb). The species shows extreme sexual dimorphism, with the male twice the size of the female.