Aggression and Population Regulation in Red Grouse

Abstract

RECENT work on red grouse (Lagopus lagopus scoticus) on a moor at about 300 m altitude in Scotland¹ indicates that the spring breeding stock is largely determined the previous autumn. Each year, cock grouse established a new pattern of territories in August–September, and the number and shape of these territories was maintained with only minor changes till the next breeding season in April–May. Any cocks which did not obtain territories in autumn did not breed the next summer, and mostly died before April. Thus the size of the breeding stock was annually determined through the birds' competition for territories. The chief problem was to find what controls the size of the territories.