Date of Award
M.S. in Biological Science
Susan L Balenger
Jason D Hoeksema
University of Mississippi
Climatic conditions are particularly important to breeding birds, especially as recent global change has caused a shift in the timing and length of avian breeding seasons. Nest microclimate has been shown to influence avian development and parental care, however, little work has been done to examine whether increased heat poses a cost to altricial nestlings at different stages of their development. We manipulated the temperature of eastern bluebird (Sialia sialis) nest boxes to examine whether or not nestlings exhibit a heat shock response, and a difference in growth or altered parasite loads at both their early and late developmental stages. We found that heated birds were in poorer body condition over the course of the treatment and gained less mass (i.e. had a decreased growth rate) in their early development relative to control birds. Overall, heat-shock protein expression did not differ between treatments, but it was upregulated with age within heated birds, suggesting that a protective response was mounted as the birds became more developed. Feather-degrading bacterial load of thirteen-day old nestlings was highly variable and unrelated to the growth and body condition of the birds, suggesting that proliferation is influenced by ambient conditions, not individual susceptibility to parasites. Overall, our findings reveal a cost posed by excessive heat as well as a signature of tolerance, expressed when the birds are more developed and nearer to fledging. Together with other literature on cavity-nesters, this study better informs our understanding of how vertebrate animals can respond plastically to unfavorable conditions in their rearing environment and highlights the need for additional examination of behavior as a mediator of development and physiology.
Sykes, Brooke E., "Nest Microclimate Manipulation Affects Growth, Development, And Heat-Shock Protein Production In The Eastern Bluebird (Sialia Sialis)" (2020). Electronic Theses and Dissertations. 1830.
Available for download on Tuesday, August 31, 2021