SEM Image of Barbules in a Feather (image) University of California - San Diego Share Print E-Mail Caption Researchers found that barbules-- the smaller, hook-like structures that connect feather barbs-- are spaced within 8 to 16 micrometers of one another in all birds, from the hummingbird to the condor. This suggests that the spacing is an important property for flight. Credit University of California San Diego Usage Restrictions Please credit University of California San Diego Share Print E-Mail 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.