Anna's Hummingbird Feeding (IMAGE) University of California - Berkeley Caption This Anna's hummingbird is trained to feed while flying in a wind tunnel so that the bird's breath can be collected and analyzed for oxygen content. Credit Christopher Clark/UC Berkeley Usage Restrictions None License Licensed content 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.