Electronic Theses and Dissertations





Date of Award


Document Type


Degree Name

Doctor of Philosophy



Committee Member

Duane McKenna

Committee Member

Matthew Parris

Committee Member

Christopher Sims


Waterfowl face a multitude of stressors across the fall and winter. These stressors include energetic demands associated with annual cycle stage, weather, habitat availability, and waterfowl hunting seasons. Stressful stimuli elicit a physiologic stress response culminating with the release of corticosterone (CORT). CORT aids in survival and recovery over the short-term, but if elevated over a long period it can lead to decrements in health. To avoid the potential harmful effects of prolonged elevations in CORT, some birds seasonally dampen their response to a predictable stressor. The aim of this study was to examine the changes in stress physiology and body condition of Mallards (Anas platyrhynchos) across the fall and wintering period. Mallards were sampled via netting or lethal take pre-migration in North Dakota and across the fall and winter in eastern Arkansas. Netted Mallards underwent a standard capture and handling protocol with blood samples taken over an hour, whereas shot Mallards had a blood sample taken immediately. Blood samples were used for plasma CORT and triglyceride (TRIG) analysis. Body mass, body condition index (BCI, mass corrected for size), and TRIG were regressed against subcutaneous fat thickness to determine which was the best indicator of fat deposits and therefore condition. While all three measures were significantly correlated with fat, BCI explained the most variation in fat deposits and therefore was used as the primary factor for assessing condition. Baseline CORT levels did not change across seasons, but body condition was reduced in Mallards across the fall into winter, and was lowest during the hunting season. Mallards had a reduced CORT response during fall migration and an increased response during the late winter, when Mallards complete pair formation. These results are similar to other species in which there were no changes in baseline CORT across seasons: a dampened CORT response during the energetically expensive periods of migration and molt, and increased responsiveness associated with breeding behaviors.


Data is provided by the student.

Library Comment

dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.