Dissertation Research: Vocal, Morphological, and Genetic Diversification in the North American Red Crossbill (Loxia curvirostra) Complex

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Vocal behavior is important in evolutionary processes in songbirds, yet few studies have attempted to explain morphological and genetic diversification in light of vocal information. This research will integrate vocal, morphological, and genetic data in the highly polytypic North American red crossbill (Loxia curvirostra) complex. This group presents an unsolved evolutionary paradox: the birds are nomadic, suggesting a high rate of gene flow, yet there is extreme diversity in bill size, body size, and plumage coloration within the group. Several testable alternative hypotheses regarding the nature of the variation in North American red crossbills will be tested. The hypothesis currently favored by ornithologists is that different forms of red crossbill are subspecies. This hypothesis, along with alternative hypotheses that the forms may be species, discontinuous morphs within breeding populations, or the result of developmental plasticity will also be examined. Data to be gathered include information on geographic variation in vocalizations, morphology, and allozymes, combined with information on mating behavior and breeding structure in populations.