Year of Award


Document Type


Degree Type

Master of Science (MS)

Degree Name

Organismal Biology, Ecology, and Evolution

Department or School/College

Division of Biological Sciences

Committee Chair

Thomas E Martin

Commitee Members

Bret Tobalske, Joshua Millspaugh


Body temperature, heat dissipation limit hypothesis, life history, long-lived, reproductive effort, tropics


University of Montana

Subject Categories



Heat production relative to dissipation rates have constrained reproductive effort and reduced fitness in short-lived, temperate birds. To determine whether heat constrains reproductive effort in long-lived taxa with low reproductive effort, we experimentally clipped plumage from tropical Gray-throated babblers (Stachyris nigriceps) to increase heat dissipation rates. Contrary to findings in short-lived species, we found no strong evidence of heat dissipation constraints on reproductive effort in our mid-elevation study. Clipped adults did not increase feeding rates compared to controls, but clipped females did spend more time incubating and brooding eggs and young. Increased time in the nest may reduce increased heat loss and energy expenditure following clipping of the belly plumage at our cool, mid-elevation study site. Furthermore, control parents in our study had lower body temperatures than songbirds that previously have been shown to be heat-limited. We suggest that heat production from the low reproductive effort of long-lived tropical songbirds may not generally be sufficient to create major thermal constraints. Ultimately, the degree to which heat limits reproductive effort may strongly depend on the environment and interspecific differences in evolved levels of reproductive effort and parental heat production during breeding.

Included in

Ornithology Commons



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