More testosterone...more sex...less life

Ok.. so while I'm on birds, here you go:

Dating and mating are unique for many species, but for dark-eyed junco songbirds, researchers led by North Dakota State University assistant biology professor Wendy Reed, Ph.D., found something new.

Published in the May issue of The American Naturalist, the team’s study found that male birds with extra testosterone were more attractive to females and produced more—but smaller—offspring. Smaller offspring had lower survival rates than larger offspring. The extra testosterone also made the male birds sing more sweetly and fly farther. The testosterone-laden birds proved irresistible to older, more experienced female juncos, but that attractiveness carried some risks. Elevated testosterone levels increased activity—possibly attracting more predators—made the male, dark-eyed juncos more susceptible to disease and shortened their lifespan. “They had lower immune function and paid a cost with lower survival rates,� said Reed.