CAREER: The evolutionary causes and functional consequences of sexual dimorphism in flight muscle size in birds

This project aims to understand why males and females of many (but not all) types of birds differ in the size of their flight muscles, and how these differences affect their flight. Flight in birds has been and continues to be an inspiration for engineers designing better flying machines, but much is still unknown about how small differences in bird anatomy, like those within a species, influence flight ability. This project also has a strong educational component: undergraduate students will be involved in all aspects of the research, learning to create hypotheses, design studies, collect and analyze data, and write up results. Students in an undergraduate biology course will create play-based vertebrate anatomy teaching materials for use in a local children’s science center and in Head Start preschool classrooms. In doing so, they will gain valuable skills in science communication while improving their understanding of anatomy. Underserved children from a rural community will benefit from new engaging educational materials designed for them. The aims of this project are to understand why many species of birds exhibit sexual dimorphism in flight muscle size, but many others do not, and to understand how this dimorphism in flight muscle size impacts flight performance in wild birds. A team of undergraduate students, a postdoc, and the principal investigator will compile a dataset of skeletal measurements of at least five male and five female specimens each for at least 1,000 species, with a complementary dataset on species life history and ecological traits, to test hypotheses about which ecological traits best predict sexual dimorphism in flight muscle size. To understand how sexual dimorphism in flight muscle size affects flight performance, high-speed video cameras will be used to measure velocity and acceleration of birds engaging in escape-style takeoffs under multiple conditions: natural, vertical, through an obstacle course, and in each of these settings while carrying additional weight. These experiments will be conducted in three different species: one in which males have larger flight muscles than females, one in which females have larger flight muscles, and one that does not exhibit sexual dimorphism in flight muscle size. The project will greatly increase our understanding of the extent and consequences of intraspecific variation, offer insights to engineers regarding the design of small aerial vehicles, and provide opportunities for students in quantitative research to prepare them for STEM careers. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.