Dark-Eyed Junco (IMAGE) Indiana University Caption Researchers studied the behaviors of free-living dark-eyed juncos during breeding season to measure variations in aggressiveness. Credit Indiana University: Kimberly Rosvall 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.