This nestling blue jay demonstrates how to keep a nest tidy. Like all newborns, baby birds poop. A lot. But if you peer into most species’ nests, there’s little to no evidence of it. So, where does the doo-doo go? It seems diaper duty is one of the most unique, understudied, and, frankly, underappreciated behaviors among birds. Perhaps you’ve glimpsed the process before: A nestling like seen here, turns its rear up and ejects a floppy white bag of poop encased in mucous: a fecal sac. The parent