Teaching Interests

General and Comparative Endocrinology
Animal Behavior
Avian Biology

Research Interests

My main research interests focus on Behavioral Endocrinology, Behavioral Ecology, and Avian Biology. At this time several new research programs are under development in my lab.

• Female ornamentation and its links to maternal effects and influences on male mate choice.

Maternal effects are, typically, non-genetic influences of a female’s phenotype on the quality of the offspring she produces. Maternal effects in birds can be influenced by the amount of steroid hormones and carotenoids deposited in eggs during yolk deposition. Circulating steroid hormones and carotenoids also influence ornament expressions in adults, making it possible that ornaments in females can indicate levels of these same components in eggs that they produce. This, in turn, may influence male mating decisions and, ultimately, the evolution of female ornamentation and egg components. My research into maternal effects female ornamentation uses the northern cardinal (Cardinalis cardinalis) as a focus species. Female cardinals possess multiple ornaments that are indicative of a variety of aspects of condition. Additionally, cardinals mate assortatively by multiple ornaments, and female cardinals perform unique displays of their ornament when being courted by a male. These findings suggest that female ornaments in cardinals are assessed during pair formation and that males may make mate choice decisions based on female ornament expressions.

• Steroid hormone influences on female intrasexual aggression

Studies of intrasexual aggression have typically focused on males and the benefits of behaving aggressively and gaining high dominance status. Testosterone is well known to increase male aggressive behavior in a variety of species. Females are also aggressive however it is unclear whether testosterone is as influential to females as it is to males. Currently, I am investigating other steroid hormones for their potential influence on female intrasexual aggression. In particular, I am interested in changes in progesterone, changes in the ratio of progesterone to testosterone circulating in the body, and neural interactions with steroid hormones and the influences of these factors on aggressive behavior.

• Song control centers in male and female birds; seasonal and sexual differences.

It is well known that birds display seasonal differences in the amount of song produced (much during the breeding season, little or none during the non-breeding season). Additionally, in most species males sing prodigiously while females sing little if at all. These differences in behavior are reflected in strong seasonal and sexual differences in the brain regions that control song. Males typically have larger regions than females, and these regions are smaller during the winter as opposed to the spring/summer. In a recent collaborative research effort I have begun investigating sex and seasonal differences in song control centers in male and female cardinals. Both sexes of cardinal sing, and they are known to sing outside of the breeding season. This research will address whether females differ from males, whether brain regions differ with season in either sex, and will investigate hormone regulation of song in cardinals.

Representative Publications

Jawor, J.M., McGlothlin, J.W., Casto, J.M., Greives, T.J., Snajdr, E.A., Bentley, G.E., & Ketterson, E.D. 2007. Testosterone response to GnRH in a female songbird varies with stage of reproduction: implications for adult behaviour and maternal effects. Functional Ecology 21:767-775.

Jawor, J.M. 2007. Testosterone in Northern Cardinals (Cardinalis cardinalis): Possible influence of prolonged territorial behavior. Auk 124:331-338.

Jawor, J.M., Young, R., & Ketterson, E.D. 2006. Females competing to reproduce: dominance matters but testosterone may not. Hormones and Behavior 49:362-368.

Jawor, J.M., Gray, N., Beall, S.M. & Breitwisch, R. 2004. Multiple ornaments as indicators of individual quality in female northern cardinals (Cardinalis cardinalis). Animal Behaviour 67:875-882.

Jawor, J.M. & Breitwisch, R. 2003. Melanin ornaments, honesty, and sexual selection. Auk 120:249-265.

McGlothlin, J.W., Jawor, J.M. & Ketterson, E.D. 2007. Natural variation in a testosterone-mediated trade-off between mating effort and parental care. American Naturalist 170:864-875.