Barn owls in nest box (IMAGE) University of California - Davis Caption A trio of barn owls peeks out of a nest box in Davis, California. A UC Davis study found the best time to clean nest boxes is in the fall, before the owls' winter breeding season. Credit Ryan Bourbour/UC Davis Usage Restrictions Credit must be given to the creator. Only noncommercial uses of the work are permitted. No derivatives or adaptations of the work are permitted. License CC BY-NC-ND Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.