<i>Science</i> Cover (IMAGE) U.S. National Science Foundation Caption The evolutionary history of birds such as the hoatzin (Opisthocomus hoazin; pictured) has been difficult to resolve. This special issue focuses on the avian phylogenomics project, which sequenced 45 bird species from all major avian clades. Using this data, studies analyzed the phylogenetic relationship of birds and explored aspects of avian biology. See page 1308. Credit Cover - Copyright AAAS 2014. Photo- Copyright Flip De Nooyer/Foto Natura/Minden Pictures/Corbis 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.