To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video Movie S4. Animation showing shape changes along PC2, in a dorsal view. The shapes of bird beaks are highly controlled by nondietary factors Jen A. Bright, Jesús Marugán-Lobón, Samuel N. Cobb, and Emily J. Rayfield PNAS. 2016. DOI: 10.1073/pnas.1602683113 Download Original Video Browse All Videos »