Date of Award

Spring 5-9-2022

Document Type


Degree Name

Bachelor of Arts



First Advisor

Dr. Natalie A. Wright


Studies on sexual dimorphism in birds are common, but generally focus on dichromatism or, occasionally, overall size dimorphism. However, many studies overlook more subtle forms of dimorphism, such as dimorphism in body shape or specific structures. Because of this, many species that are assumed to be sexually monomorphic based on similarity in plumage or body mass are, in fact, dimorphic. Our previous research indicates that one particularly overlooked aspect of avian sexual dimorphism is differences in relative flight muscle size. We set out to examine how widespread dimorphism in the avian locomotor system is, particularly the flight and leg skeletal complexes, and to determine which aspects of life history and ecology best predict size and shape dimorphism. Using phylogenetic comparative methods and skeletal and ecological data for 189 species from 84 families we show that mating system, parental incubation investment, and parental division of labor in nest construction correlate with dimorphism in flight structures, with greater female parental investment predicting larger male flight structures, and greater male parental investment predicting larger female flight structures.

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honorsthesissuptable.csv (82 kB)
Species dimorphism measurements nad life history data.