Ledger of Bird Measurements (image) Field Museum Share Print E-Mail Caption One scientist, Dave Willard, took the measurements of the 70,716 bird specimens in this study and recorded them by hand into ledgers like this. This photo shows one of Willard's ledgers, his measuring tools, and a Tennessee Warbler. Credit (c) Field Museum, Kate Golembiewski Usage Restrictions Please include credit: (c) Field Museum, Kate Golembiewski 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.