Song Sharing in a Group-Living Songbird, the Australian Magpie, Gymnorhina Tibicen. Part Iii. Sex Specificity and Individual Specificity of Vocal Parts in Communal Chorus and Duet Songs

Abstract

In this paper we continue our study of the role of song in the social behavior of a cooperatively living songbird, the Australian magpie, Gymnorhina tibicen (Cracticidae). In this species, all members of a cooperative group sing and fight together in defense of their territory. Communal chorus songs consist of loud carol syllables; each individual sings a particular vocal role. We sampled the song repertoires of 24 magpies in 12 territorial groups in Queensland, Australia, and of 12 magpies in 4 territorial groups in the Manawatu region of New Zealand. Our results include: 1. Description of duet and chorus song. Carol portions of song are usually preceded by an introductory warble segment. Carol syllables are diverse in physical structure. We grouped 204 distinct carol syllables into 11 general classes. 2. Between-sex differences in syllable repertoires. Some syllable classes were sex-specific, and a few were sung by magpies of both sexes. Female-specific syllables were more complex structurally than those of males. Females had significantly (p 0.5) in the average percentage of the repertoire shared between same-sex birds who were vs were not territorial neighbors at our Queensland study site. 4. Carol song repertoires. The number of duet song types in each group's repertoire varied widely from group to group. Females had significantly (p<0.05) larger song repertoires than their mates. 5. Carol development in young birds. A young magpie seemed to sing variants of the carol syllables of only one parent, perhaps the same-sex parent, and echoed the parent's carol syllables during communal choruses. 6. Geographic variation in carol syllables. Carol syllables of individuals at our New Zealand study site were also sex-specific, and could be grouped into general classes. No syllables were the same as those recorded from the Australian study birds. 7. Song context. We compared the amount of time magpie groups spent warbling, warble-caroling, and not singing, during five commonly occurring types of contexts. Warbles were most frequent in nonaggressive intragroup contexts. Warble-carols were most frequent in aggressive intergroup contexts. We discuss the function of song in social cohesion, and group and individual recognition ; evolution of duet song; singing behavior of females; and mechanisms of vocal learning.