Dark-Eyed Junco Nestlings (IMAGE) Indiana University Caption How often a dark-eyed junco father feeds his young depends on his tendency toward testosterone-fueled aggression. Credit Joel McGlothlin 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.