Correlates of Song Organization Among North American Wrens

Abstract

Of the nine North American wrens, the house, winter, Bewick's, Carolina, cactus, and canyon wrens repeat a song type several times before changing to another, that is, AAA... BBB..... The rock, long-billed marsh, and the short-billed marsh wrens use frequently or exclusively song organizations involving more immediate variety, for example, ABCABC... MNOMNO.... These latter three wrens have larger song repertoires and occur in high densities in communities of low avifaunal diversity, where intraspecific interactions are likely to be more frequent and intense. Rates of presentation of new song types to conspecifics are highest in the long-billed marsh wren, a very polygynous species; and, of the six AAA... BBB... songsters, the winter wren is the most polygynous (according to European studies); has by far the longest and most complex songs; and, during a song bout, spends the highest percentage of time actually singing. Such correlations suggest that (1) strong sexual selection in polygynous mating systems and (2) high encounter rates within dense wren populations have been selective forces in the evolution of large song repertoires and complex singing behaviors.