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. Found across Europe and Asia, this spectacular ground-living forest bird is renowned for its mating display. The United Kingdom population, confined to the pine forests of Scotland, is in rapid decline and threatened with extinction. However, individuals in Northern Europe and Asia number in the millions, and therefore the worldwide population is categorised as "Least concern".