Reproductive Behavior by a Female Songbird: Differential Stimulation by Natal and Alien Song Dialects

-The responsiveness of female White-crowned Sparrows (Zonotrichia leucophrys nuttalli) to male songs in their natal dialect (Clear) or in an alien dialect (Buzzy) was evaluated by measuring string-gathering and papershredding in a laboratory experiment. Females hearing Clear dialect songs gathered more strings than did females hearing Buzzy dialect songs. More females hearing Buzzy songs shredded paper than females hearing Clear songs. Both groups placed more strings than paper shreds into nest cups, indicating that strings were regarded as a more suitable nesting material. Taken together, these results suggest that females are reproductively more responsive to the song of males in their natal dialect than to-songs in an alien dialect Female songbirds’ responsiveness to male song has been measured in various ways, including the amount of nest-building, number of eggs laid, and extent of copulatory posturing. Kroodsma (1976) found that female Canaries (Serinus canaria) exposed to playback of large (normal) song repertoires of male Canaries gathered more strings (an index of nest-building activity) and laid more eggs than did females hearing playback of artificially produced small repertoires of male Canaries. Nest-building, or string-gathering, was first used as an assay by Follett et al. (1973) to determine the effect of changing photoperiod on nest-building activities. In a comparison between species, Hinde and Steel (1978) found that female Canaries responded with increased nest-building activity when hearing male Canary song but not when hearing male Budgerigar (Melopsittacus undulatus) songs. from their natal dialect region and to songs of males from alien dialect regions (Baker et al. 198 1). Another method of analyzing the female response to male songs from different dialects is to study the hormone-induced song of a mated female (Baptista and Morton 1982) and determine if the song is similar or dissimilar to that sung by her mate. A different approach to considering female responsiveness to dialects is to ask whether or not a female hearing a natal dialect is physiologically more stimulated than one hearing a non-natal dialect. To broaden the base of empirical evidence on female responsiveness to natal and alien dialects, we conducted a simple laboratory experiment to measure the nest-building activities of females exposed to playback of male songs from either their natal or an alien dialect region. Male White-crowned Sparrows (Zonotrichia leucophrys) of a particular geographical region usually sing a stereotyped song that differs in syllabic content from songs of males in other regions. These differing song populations are called “dialects” (Marler and Tamura 1962). It has been hypothesized (Marler and Tamura 1962) that song dialects in some avian species might induce birds to breed in their natal area because the birds would be attracted to their familiar natal dialect. One behavioral mechanism that might be involved in such an attraction is for the female to select a mate who sings the dialect of her natal area (Konishi