SINGING IN RELATION TO SOCIAL-DOMINANCE AND TESTOSTERONE IN WHITE-THROATED SPARROWS

Singing by white-throated sparrows Zonotrichia albicollis during the w inter in natural situations occurred most frequently among birds with high rank in a dominance hierarchy. Genetic morph, age and sex had no significant influence on singing during winter. Among testosterone-imp lanted birds in small groups in large aviaries, dominance rank strongl y influenced singing. Testosterone-treated birds with top rank sang mo st frequently, those with second rank less, and those with lower rank never. As a testosterone-treated bird's rank changed in the course of regroupings with new opponents, its frequency of singing also changed. Dominance in a group thus interacted with testosterone to promote sin ging. In addition, grouped birds in May before treatment with testoste rone did not sing. As a consequence, it seems likely that the normal s easonal development of territorial behavior and singing involves casca ding interactions of endocrine states and social circumstances.