Effects of clutch size on incubation efficiency and nest attentiveness in passerines
Small birds may incur fitness costs associated with incubating a larger clutch that have been largely ignored in previous studies attempting to explain variation in avian clutch size. In this project, we are evaluating these potential limits on clutch size acting during the incubation period. We are examining the effect of clutch size on egg temperature and the number and duration of daily foraging bouts off the nest by conducting clutch-size manipulations in two passerines that commonly breed in the pine-oak and mixed-conifer woodlands of southeastern Arizona: Red-faced Warblers (Cardellina rubrifrons) and Yellow-eyed Juncos (Junco phaeonotus). These species are relatively common breeders in the pine-oak and mixed-conifer woodlands of southeastern Arizona. In addition to clutch manipulations, we propose to test the extent to which common nest predators locate nests through visual observation of adult activity. We are examining this by comparing rates of nest predation between two sets of nests: active nests (nests with eggs and normal adult activity) and nests where we force parents to renest (nests with eggs but no adult activity).
