Hummingbird Hovering (video) University of California - Riverside Loading video... Caption The video shows that the hummingbird produces two trails of vortices -- one under each wing per stroke -- that help generate the aerodynamic forces it requires to power and control its flight. Credit Altshuler Lab, UC Riverside. Usage Restrictions None 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.