SONG OUTPUT AND STIMULATION OF THE FEMALE IN WHITE-THROATED SPARROWS

We investigated the importance of song length and singing rate in stimulating female white-throated sparrows, Zonotrichia albicollis. In November 1988 ten female and one male white-throated sparrow were captured during the fall migration. To enhance the expression of sexual receptivity, the females were implanted with 17-beta-estradiol silastic pellets. Using the visual stimulus of a non-singing male to further enhance the expression of sexual receptivity in the females, we found that females gave a greater response, in the form of copulation displays, to a five-note versus a two-note version of a typical male white-throated sparrow song. Each version was played back at four songs per minute. In May 1990 birds were captured and treated as before, except that the two-note song was played at ten songs per minute and the five-note song at four songs per minute. Therefore, each female heard twenty notes per minute. In the second experiment, the females did not show a statistical difference in response to the two- and five-note song playbacks. We interpret the results of the second experiment as indicating the song rate as well as song length is important in stimulating female white-throated sparrows because increasing the rate of the two-note song brought the response up to the level of response we obtained to the five-note song played at the slower rate. We conclude that in white-throated sparrows, song output is important for female stimulation.