Because of the constant threat of nest predation, safe sites for breeding are highly prized by cavity nesting birds. Indeed, successful cavities are often reused repeatedly, even among species that can excavate their own cavities. However, successful nest sites also harbor substantial populations of ectoparasites that have detrimental effects on the growth and health of nestlings. Multiple-brooded secondary cavity nesters could thus minimize parasite loads on subsequent broods by avoiding recently used cavities. By presenting bluebirds with different pair-wise choices of boxes in which to nest, we addressed the following questions: 1) Do bluebirds avoid soiled nests? 2) Do bluebirds prefer successful cavities? 3) Are bluebirds sensitive to predation risk? 4) Do bluebirds weigh parasite and predator avoidance differently?
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