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Exaggerated Traits and Breeding Success in Widowbirds

A Case of Sexual Selection and Evolution


J. Phil Gibson
Department of Biology and Department of Microbiology & Plant Biology
University of Oklahoma


Sexual selection has led to the evolution of interesting traits and behaviors in many animal species. In widowbirds, males undergo a dramatic change in plumage coloration and produce exceptionally long tail feathers during the breeding season. This change in appearance has facets of both intrasexual and intersexual selection. As students work through this interrupted case, they develop hypotheses and propose corresponding experiments. They are then presented with data from actual experiments on sexual selection in widowbirds that they must analyze and interpret. Developed for introductory-level biology students, the case could be adapted for upper-division ecology and evolution courses.

  • Explain the fundamental features of natural selection.
  • Explain the process of natural selection in terms of sexual selection.
  • Develop hypotheses for experiments testing intrasexual and intersexual selection.
  • Gain experience interpreting data from different experiments and then use those data to evaluate hypotheses and develop ideas for further experiments.
  • Gain an understanding of trait variation among individuals.
  • Develop ideas regarding statistical testing (undergraduate upper-division majors).
Keywords: Widowbirds; bird; natural selection; evolution; sexual selection; intrasexual selection; intersexual selection; sexual dimorphism; handicap hypothesis; experimental design
Topical Area: Scientific method
Educational Level: High school, Undergraduate lower division, Undergraduate upper division
Formats: PDF
Type/Method: Interrupted
Language: English
Subject Headings: Evolutionary Biology   Ecology   Zoology  
Date Posted: 0611/08
Date Modified: N/A
Copyright: Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

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The following video(s) are recommended for use in association with this case study.

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