Editor's Note: The history of community science in this country runs back more than a century, driven by a chain of creative, obsessive thinkers, leading armies of passionate volunteers. Read about two other innovators who have led the charge in studying birds, Chan Robbins and Jessica Zelt. It was a bright, breezy day in late April, the flowering azaleas having finally shrugged off the winter that overstayed its welcome, when Sam Droege sailed onto the grounds of the U.S. National Arboretum in Washington, D.C., behind the wheel of a pterodactyl. It was actually a '98 forest-green Saturn, which Droege had painted with yellow wings and a red-and-yellow beak that tapered to a point down the center of the hood. A piece of wood, lined with a rusty crosscut saw, had been bolted to the roof: the crest. Little jingle bells, inspired by richly adorned buses in Pakistan, dangled from chains screwed into the rear bumper. Droege still had designs for neon undercarriage lights, and...