Environmental conditions and individual strategies in early life may have a profound effect on fitness. A critical moment in the life of an organism occurs when an individual reaches independence and stops receiving benefits from its relatives. Understanding the consequences of individual strategies at the time of independence requires quantification of their fitness effects. We explored this period in the Red Grouse ( Lagopus...

A central issue in ecology is in understanding the relative influences of intrinsic and extrinsic effects on population regulation. Previous studies on the cyclic population dynamics of red grouse ( Lagopus lagopus scoticus ) have emphasized the destabilizing effects of either nematode parasites or territorial behaviour and aggression. The potential interacting effects of these processes, mediated through density‐dependent, en...

Populations of red grouse ( Lagopus lagopus scoticus ) undergo regular multiannual cycles in abundance. The ‘kinship hypothesis’ posits that such cycles are caused by changes in kin structure among territorial males producing delayed density‐dependent changes in aggressiveness, which in turn influence recruitment and regulate density. The kinship hypothesis makes several specific predictions about the levels of kinship, aggres...