Fecal corticosterone levels in California spotted owls exposed to low-intensity chainsaw sound

The California spotted owl (Strix occidentalis occidentalis) is a focal management species in Sierra Nevada national forests. To protect the owl from human activity, the United States Forest Service has proposed guidelines that would prohibit timber harvest and road or trail construction within 400 m of active owl nest sites during the breeding season. To guide these efforts, we tested the physiological stress response of 9 nonbreeding wild male owls to the sound of a chainsaw operated 100 m from their roost site, using change in fecal corticosterone level (ng/g dry feces) as the response variable. We employed a cross-over experimental design to control for differences among individuals. Chainsaw exposure did not result in a detectable increase in fecal corticosterone level (F_1,7=0.01, P=0.94). These findings corroborate results of a field study that suggested spotted owls can tolerate low-intensity human sound in their environment without eliciting a physiological stress response. However, activities producing chronic and intense noise (e.g., timber harvest, road construction), which might elicit such a response, were not simulated in our experiment. The effects of these activities on California spotted owls will require further research.