Year of Award


Document Type

Thesis - Campus Access Only

Degree Type

Master of Science (MS)

Degree Name

Wildlife Biology

Department or School/College

College of Forestry and Conservation

Committee Chair

Thomas E. Martin

Commitee Members

Art Woods, Kerry Foresman


bactericidal activity, immune function, natural antibodies, passerines, trade-offs


University of Montana


Why species differ in rate of development and quality of offspring is a central question in life history theory. A physiological trade-off is thought to occur between the rate of development and enhancement of internal systems, such as immune function, which determine high offspring quality. For example, in birds, slow rate of embryonic development is thought to enhance immune function; however, tests of the trade-off show mixed results for adult and nestling birds. A problematic assumption of previous tests is that the length of the embryonic period represents the intrinsic rate of embryonic development. Evidence indicates that temperature experienced by the avian embryo influences rate of development such that cool temperatures slow development, extend development period and may even compromise offspring quality. We studied coexisting species of passerines to test predictions that species with slower embryonic development have higher measures of immune function. We used the absolute length of embryonic period and temperature-corrected embryonic period as measures of rate of development. We also tested the prediction that species with higher parasite attack evolved stronger immune function. We found that among species, measures of adult immune function are positively related to the absolute length of embryonic period but not to temperature-corrected embryonic period. One measure of adult immune function was explained by intestinal parasite intensity suggesting these parasites may exert a selection pressure on certain components of immune function. Nestling immune function was not related to the absolute length of embryonic period while one component of nestling immune function was positively associated with temperature-corrected embryonic period. The discord between nestling versus adult immune function and their relationship with absolute length of embryonic periods raises questions about the importance of embryonic development in determining adult immune function. Our results suggest that a physiological trade-off may be occurring between rate of development and certain aspects of the immune function.

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