Testosterone implants increase song but not aggression in male Lapland longspurs

摘要

Lapland longspurs, Clcarius lapponicus, are tundra-nesting arctic birds with an extremely short breeding season. Males show a pronounced brief peak of plasma testosterone early in the season. We studied the effect of exogenous testosterone on song and aggression in free-lining male Lapland Longspurs. We gave high-testosterone implants to 16 birds, low-testosterone implants to seven birds, And empty or no implants to 33 birds. The implants resulted in significantly different plasma Testosterone levels during incubation (high-testosterone mean=20.79±3.4 ng/ml, low-testosterone Mean=2.54±0.5 ng/ml, control mean=0.53±0.1 ng/ml).