Physiological, life history, and behavioral responses of a breeding bird community to experimentally reduced nest predation risk

The role of nest predation in shaping avian life history strategies remains conspicuously untested by broad experiments that alter environmental risk of nest predation; despite the fact that nest predation is a major source of reproductive failure. We examined whether parents preferentially settle in safer nesting environments and adjust their reproductive strategies to local risk. We experimentally reduced nest predation risk and show that 8 species of migratory passerines prefer to nest in areas with reduced risk of nest predation. Parents of 12 species of passerines nesting in these safer environments increased investment in their young through increased egg size, clutch mass, and the rate they fed nestlings, and also increased investment in female condition by increasing the rates that males fed incubating females at the nest, and decreasing the time that females spent incubating. Although nest predation risk decreased with predator reduction, it did not decrease as significantly as predicted. We show that reproductive potential was not limited by the increased expression of risky behaviors as theory may have predicted, and suggest compensatory mortality as a likely alternative. Despite clear changes in reproductive strategies, we failed to find any influence of nest predation risk on baseline corticosterone levels either between treatments or across species that differ in risk. These results demonstrate that birds can assess nest predation risk at large and that nest predation plays a key role in the expression of avian habitat selection and reproductive strategies, but the physiological mechanisms regulating these changes remain unclear. Finally, in hope of imparting our understanding of the natural world to the next generation we designed an innovative lesson plan to teach children about microclimate, an important abiotic influence on natural communities.