Millions of years ago, scaly, lizard-like dinosaurs ruled the Earth. Over time, some of those dinosaurs sprouted feathers and took to the skies—and while their reptilian cousins died off, those ancient avians survived to become the birds we know and love today. Recent decades have seen an explosion in research uncovering new details about the prehistoric birds that once roamed the planet and the evolutionary journey that brought them into the modern age. Cutting-edge technology has played a crucial role, says Daniel Field, who studies bird evolution at the University of Cambridge. Advanced scanning methods can capture minute details from fossil samples, while large-scale genome sequencing helps dig into the evolutionary relationships that tie together this whole family tree. In many ways, the steady flow of research continues to complicate the picture of bird evolution, says Jingmai O’Connor, a paleontologist and curator at Chicago’s Field Museum. “It was easier for us...