Restrictive mate choice criteria cause age-specific inbreeding in female black grouse, Tetrao tetrix

► We tested whether age-specific inbreeding in female grouse is random with respect to kinship. ► We used random mating models with different mate choice criteria. ► Mating is random with respect to kinship. ► Restrictive mate choice increases inbreeding in old females. ► Mate fidelity reduces inbreeding risk.