Male Singing Ability and Territory Integrity in Red-Winged Blackbirds (Ageliaus Phoeniceus)

Abstract

AbstractDuring the breeding seasons of 1974 and 1976 three territorial male Red-winged Blackbirds were devocalized utilizing a technique which involved cutting the membrane of the interclavicular air sac. As a result, males were devocalized or muted for a period ranging between 14 and 21 days, after which time they regained their ability to sing typical song. One sham operated male and 10 "undisturbed" neighbouring residents served as control males. The frequency and length of intrusions by a devocalized male's neighbours increased markedly during a male's mute period. Sidling, a highly visual and apparently aggressive behavior, increased dramatically during the time a male was muted. After the experimental males regained their ability to sing species typical song they were successful in regaining territory boundaries which approached or exceeded the pre-operative dimension. It was concluded that 1) under the conditions of this study muted males were not as effective in excluding potential or actual intruders from their territories as when they could produce song; 2) visual dispalys (sidling) are utilized more frequently by devocalized males because of the persistence of intruding males on devocalized males' territories.