How do hormones like testosterone coordinate important activities in an animal’s life, and how might those activities tradeoff with one another? How do the microbial communities living on birds affect the scents they give off, and how do those scents influence the birds’ choices of mates?

In this episode, we talk with Ellen Ketterson, an evolutionary biologist at Indiana University, Bloomington, about her work on juncos in North America. We discuss Ellen’s early research on how testosterone modulates life history characteristics of male juncos. We also discuss her more recent work on bird microbiomes and their roles in bird olfaction and mating, and the physiological underpinnings of migratory behaviors. Finally, we talk about some big ideas about the philosophy of doing biology -- including the value of building scientific efforts around model versus natural systems, paths to integration in biology, and how to mentor students effectively.