Ledger (IMAGE) Field Museum Caption Dave Willard's ledger of birds added to the museum's collections, with a measuring tool and a Tennessee Warbler specimen. Credit Kate Golembiewski, Field Museum Usage Restrictions Please include credit to Kate Golembiewski, Field Museum 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.