The effects of androgen and antiandrogen on dominance and aggressiveness in male red-winged blackbirds

Male red-winged blackbirds were given implants of testosterone or flutamide in order to manipulate the level of androgen reaching receptor sites. Implants of cholesterol were given as controls. Radioimmunoassay showed higher levels of testosterone and DHT in the plasma of testosterone-implanted birds than in the plasma of the pooled flutamide-implanted and cholesterol-implanted birds. Dominance was significantly correlated with effective androgen level. Androgen level was not correlated with rates of supplantations per subordinate but was correlated with rates of escalated attacks per subordinate. Thus androgen level influences dominance in male red-winged blackbirds by influencing one component of aggressiveness.