- Behavioral endocrinology of a residential, long-term territorial songbird: Testosterone is well-studied for its impacts on aggressive and parental care behaviors in birds. Studies with Northern Cardinals (Cardinalis cardinalis) have found that both sexes express testosterone during the whole year (typically testosterone is expressed at measureable levels only during the breeding season in birds) and that testosterone may not impact aggression and parental care in a fashion similar to other species studied (e.g., aggression and testosterone do not co-vary). Studies are on-going to understand how testosterone functions as a behavioral modifier in cardinals.
- Situational behavioral responses in Northern Cardinals: Because cardinals are behaviorally aggressive to intruders, but because testosterone does not always increase during aggressive interactions studies in my lab are now addressing whether behavior and hormone increases are situational. Specifically we are testing whether known neighbors are more threatening than strangers and whether neighbors require a different level of behavioral response when they intrude onto focal territories.
- Disturbance, hormones, and behaviors in Eastern Bluebirds (Sialia sialis): Typically avian species experience human presence and activities as detrimental (e.g., reduction in habitat, introduction of atypical predators and competitors). However some species find human modified habitats useful; for example the preference for short-grass prairie as a forging habitat brings the Eastern Bluebird preferentially into human modified lawns. However human-modified habitats can differ strongly in human presence and activity. We are currently assessing aggressive and reproductive behaviors, and the hormones testosterone and corticosterone in male and female Eastern Bluebirds in human modified habitats that differ in human activity to determine if the presence of humans in modified environments is perceived differently and whether this impacts physiology.
DeVries, M. S. and Jawor, J. M. 2013. Natural variation in circulating testosterone does not predict nestling provisioning rates in the northern cardinal, Cardinalis cardinalis. Animal Behaviour 85:957-965.
DeVries, M.S., Winters, C.P., & Jawor, J.M. 2012. Testosterone elevation and response to gonadotropin-releasing hormone challenge by male Northern Cardinals (Cardinalis cardinalis) following aggressive behavior. Hormones and Behavior 62:99-105.
DeVries, M.S., Holbrook, A.L., Winters, C.P., & Jawor, J.M. 2011. Non-breeding gonadal testosterone production of male and female northern cardinals (Cardinalis cardinalis) following GnRH challenge. General and Comparative Endocrinology 174:370-378.
McGlothlin, J.W., Whittaker, D.J., Schrock, S.E., Gerlach, N.M., Jawor, J.M., Snajdr, E.A. & Ketterson, E.D. 2010 Natural selection on testosterone production in a wild songbird population. American Naturalist 175:687-701.
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.
Jawor, J.M. 2007. Testosterone in Northern Cardinals (Cardinalis cardinalis): Possible influence of prolonged territorial behavior. Auk 124:331-338.