This much we know: Modern birds evolved from some dinosaurs. But when did birds become, well, birds? And how? Scientists have been asking these questions for decades, and now a new study seems to be putting them one step closer to the answer. But first, some background. To find out how certain dinosaurs evolved into birds, scientists study the relationships and connections between the two along the tree of life, a diagram of the evolution of all living things, using a technique called phylogenetics. Although this process has provided valuable information, there are many differences between modern birds and their ancestors that keep scientists puzzled. A big one is reproduction. From egg size to parental care, the way birds reproduce today is dramatically different from the way their ancestors reproduced. Figuring out when the reproductive sysems of dinosaurs began to evolve has long been a goal for researchers. A paper published last week in The Auk: Ornithological...