Badge size, phenotypic quality, and reproductive success in the house sparrow: a study on honest advertisement

Abstract

Honest signaling theory suggests that advertising traits must be costly to their bearer; thus, only individuals of high phenotypic quality can exhibit maximal expression of these traits. Males of the sexually, dichromatic house sparrow Passer domesticus have a black throat patch that functions as a badge of status. Badge size increases with age and decreases with advancing fledging date in yearling males; thus, badge size was larger in older individuals even though age differences were small. Badge size also increased with physical condition independent of age. Badge size functions as an honest signal, possibly because there are costs involved in its production. Males with enlarged badges acquired more nest sites than either control males or males with reduced badges. However, males with enlarged badges possessing a nest site raised fewer fledglings per year than did males with reduced badges, suggesting that cheating has no selective benefit. -from Author