Dyed birds achieve higher social status than controls in Harris' sparrows

The status-signalling hypothesis has been proposed to explain colour variation among individuals in flocking birds. Its fundamental assumption is that colour may affect the determination of an individual's social rank in a flock. Here I show for winter Harris' sparrows (Zonotrichia querula) that birds dyed to resemble adults dominate control birds within experimental flocks of young males and young females. The domination of controls by the dyed birds was achieved by a two-step process in both experiments: immediately after the two groups were combined, the controls avoided the dyed birds; then, shortly thereafter, the dyed birds began actively to displace the control birds.