Personality and Fitness in Eastern Bluebirds and Tree Swallows


     My post doctoral research focused on understanding the evolutionary significance of personalities in eastern bluebirds and gaining knowledge of and techniques in behavioral endocrinology. I conducted my post doc work under the guidance of Dr. Ellen Ketterson at Indiana University. Differences in personalities similar to those familiar in humans (i.e. assertive, friendly, or aggressive) have been documented in wild animals including two species that I study: Eastern bluebirds and Tree swallows. In these species, my students and I are studying whether personality affects mate-choice decisions, fitness and competition for breeding resources between conspecific and heterospecifics.

     Tree swallows are extending their range southward and have been in the NC study area <40 years. At our field site, bluebirds and tree swallows are extremely aggressive towards one another and often the result of competition between tree swallows and bluebirds is eviction of the bluebird pair from the nest box. Morgan Harris' MS thesis (2014) demonstrated that bluebirds tend to mate with individuals of similar personality type. Further, he showed that interspecific competition between tree swallows and bluebirds influences the fitness benefits of pair similarity in personality (Harris & Siefferman 2014). This research can be used to shed light on how interspecific competition with aggressive invasive species can exert selection pressure on a less-aggressive, resident species and has far-reaching application in how behavior affects the vulnerability of species to invasions. We are trying to get a handle on why tree swallows are undergoing such a fast-paced range expansion. My current graduate student, Alex Albers, is studying how personality types vary across the breeding range and how hormones are associated with aggression and dispersal in tree swallows.

     Kristen Content a current graduate student is focusing on how stress hormones might dictate how individual tree swallows mediate aggression. She is investigating consistency in hormone profiles and aggressive behavior in tree swallows. Tyler Pyle, an undergraduate honors students, is studying the fitness consequences of assortative mating for personality in tree swallows.

     I am also interested in how personality influences maternal effects. Using tree swallows, my former MS student, Alex Bentz found that females breeding in high density environments are more aggressive and deposit more androgens in egg yolks. She showed with an elegant experimental design that those yolk androgens have both short and long term effects on offspring behavior and growth (Bentz et al. 2013).