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A Contextual Analysis of Two Song Variants in the Bobolink

1983; Oxford University Press; Volume: 85; Issue: 2 Linguagem: Inglês

10.2307/1367252

1938-5129

James F. Wittenberger,

Avian ecology and behavior

Male Bobolinks (Dolichonyx oryzivorus) sing two variants of primary song, with the shorter beta variant being a derivative of the longer alpha variant. The beta song is sung most frequently during territory boundary disputes and at times of day and season when territory conflicts are most intense. The alpha song is sung most frequently during preterritorial displays, when unmated females are in the area, and during courtship. The proportion of song types given during courtship progressively shifts toward more alpha songs from day 1 to day 4 of the mating process. During circle flights, which are directed specifically toward females, alpha songs are given almost exclusively. Hence, the beta song apparently conveys a more aggressive message than the alpha song. Further analysis shows that length of song sequences (i.e., degree of fragmentation or compounding of songs) is associated with intensity of the signal. Analyses of the structural differences between the two song variants and the patterns of song fragmentation lead to several predictions regarding the meaning of particular song syllables. Present evidence indicates that the introductory notes convey information about individual identity, possibly species identity, and song type identity. The next whistled segment apparently conveys information that serves to attract the attention of females, while the long warbled syllables that comprise much of both song types convey primarily an aggressive signal. Several hypotheses regarding the evolution of multiple song types are discussed in light of the data for Bobolinks. The Beau Geste and status signalling hypotheses do not seem applicable to this species. The significance of aggressive behavior during courtship is also discussed.