Seeing red: uncovering coverable badges in red-winged blackbirds

The coverable badge hypothesis predicts that non-territorial floaters should conceal their badges and that territory owners should expose their badges. Evidence is presented that suggests owners also benefit by concealing their badges at certain times. Forty territorial male red-winged blackbirds, Agelaius phoeniceus, were randomly assigned to one of two clipping treatments. The scapular feathers that cover the epaulettes of experimental males were clipped so that the epaulettes were continuously exposed (clipped males). Contour feathers near the epaulettes were clipped on control males. These contour feathers are not used to cover the epaulettes. Clipped males spent more time chasing intruders (particularly neighbours) from their territories than control males. Clipped males also trespassed on the territories ofneighbours less often than control males. These results suggest that owners that conceal their covetable badges enhance their ability to trespass on the territories of other males. Owners may also benefit from being able to conceal their coverable badges while on their own territories because continuous display of aggressive badges may inappropriately signal combativeness, resulting in more aggressive interactions with other males, particularly neighbours.