The
western capercaillie (
Tetrao urogallus), also known as the
wood grouse,
heather cock or just
capercaillie , is the largest member of the
grouse family. The largest known specimen, recorded in captivity, had a weight of . 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".