Variation of repertoire use in the eastern meadowlark, Sturnella magna

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Abstract
The singing behavior of 9 eastern meadowlark (S. magna) males was examined over the 1980 breeding season for changes in versatility (use of different song types and switching between song types). The greatest degree of versatility occurred during territorial defense; the use of 1-song bouts rose from 33.1% during nonchase periods to 64.9% during intraspecific encounters. Versatility also showed a seasonal trend, peaking during courtship and decreasing through the incubation, nestling and fledgling stages. No relationship was evident between versatility characteristic of a male and the number of females obtained. While versatility may have increased during encounters with both sexes, it apparently did not influence mate attraction. These results are consistent with the hypothesis that repertoires reduce habituation in listeners. The data also support a derivative explanation that song variety serves as a graded signal indicating the tendency of a singer to interact with other males and females.