Flycatcher egg (IMAGE) University of Turku Caption Flycatcher egg being illuminated in order to inject thyroid hormones specifically into the egg yolk. Credit Tom Sarraude Usage Restrictions Please attribute the photo to Tom Sarraude. 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.