Mechanisms of Habitat Selection in a Specialist and A Generalist Species of Sparrow

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Considerable ecological theory is directed towards the use of habitat by potentially competing species and how this might change with varying resources and community composition. Much less work has been conducted on the basis of habitat responses and the formation of habitat preferences. However, understanding the proximate basis of habitat selection is critical in determining how readily animal species can respond to observed environmental changes. The focus of this project is the determination of factors that influence habitat selection and the differences in ecological plasticity found in two closely-related sparrow species. A series of experiments will be done to determine the differences in intrinsic habitat responses in the Song (Melospiza melodia) and Swamp (M. georgiana) sparrows. The Song Sparrow is one of the most widely distributed North American bird species, occuring in a variety of scrub and marsh havitats. It is well established in human-altered habitats such as agricultural fields and cities and is also a frequent colonizer of small islands. The Swamp Sparrow is relatively specialized occuring mainly in marsh or marsh-like habitats. Based on field observations and experiments, the focus of the laboratory experiments will be on the response of sparrows to water, cover, and novelty. Differences in responses between species in wild- caught immatures will be uncovered and the responses of hand- reared sparrows raised under identical laboratory conditions will be tested. Because neophobia provides a relatively simple mechanism for regulating the degree of ecological plasticity in animals, its study will be emphasized. Experiments will include preliminary work on the use of heart-rate telemetry to measure a physiological correlate of fear-responses of sparrows to novelty. Methods to be perfected during the study could be used for a variety of other topics in vertebrate ecology.