Parasites are important selective factors in evolution, yet studies of their ecology and effects on bird host behavior have concentrated on colonial species. This study will be the first documentation of the importance of a nest parasite to the evolutionary biology of a solitary breeding bird host. Because western bluebirds breed in boxes which permit ready access to nests we can measure experimentally the impact of blood-feeding larvae of a specialist blowfly, Protocalliphora sialia, on its hosts. In general, fly parasites affect nestling blood condition, growth rate and survival. We will study these effects as well as parental feeding behavior and nest-site choice as defenses against parasites. In addition, we will evaluate fly use of forest edge habitats produced by disturbance, such as roadways which provide flight corridors. We will compare the ability of flies to locate nests along the open edges of woodland fragments versus nests within intact sites. The importance of these data in contributing to knowledge of host-parasite interactions in nature is enhanced by the relevance of the effect of habitat disturbance on transmission of parasites and diseases in endangered species and humans.
