| Nest site selection and reproductive behaviors have likely evolved responding to diverse selective factors, nest predation and microclimate being major mechanisms. Here I address behavioral responses of breeding song birds to variable ecological and environmental factors. I focus on how nest predation and microclimate, independently or in concert, influence breeding behaviors like nest site selection, incubation and nestling parental care in an open-cup nesting passerine. I analyze fitness consequences of variation in those behaviors and make inferences about their adaptiveness. A Channel Island endemic subspecies of Orange-crowned warbler, which nests at variable heights, and is exposed to contrasting predator communities, provided a model system to address the following questions: -How nest predation risk from different predators types shape nest site selection and nest activity; -Do individuals modify breeding behaviors in the short term in response to different kind of predators? -How does long term exposure to different predator communities shape behavioral responses during various breeding stages on two warbler populations? -How incubation behaviors vary relative to nest site, and which are the consequences of such behaviors in the context of microclimate demands of the selected site? -Which is the influence of past reproductive experience on a bird's site selection process, and which are its consequences?; Results from an experimental manipulation of nest predation risk show that such is a strong factor shaping nest site selection and behavioral activity at nests. Presence of different types of nest predators, aerial vs. terrestrial, favor opposing nesting patterns (ground nesting or above-ground nesting respectively), and contrasting reduction in nest activity. A comparative analysis of warbler populations exposed to different predator communities further support that risk from aerial-visually oriented predators vs. terrestrial predators elicit contrasting behavioral responses, suggesting a sophisticated ability to assess the fitness costs and benefits of different behaviors. Microclimate also appears as an influential factor driving breeding behaviors in birds. Variable ambient temperature at different nest heights resulted in distinct incubation patterns, further influencing incubation period. Past reproductive experience appeared as an important factor shaping nest site selection, yet, fate of previous nest failed to provide accurate cues for future success. |
