Somewhere between one and 49: That’s how many adult Stresemann’s Bristlefronts are thought to be left in the world. These figures weren't pulled out of a hat. They’re based on meticulous searches and a decades-long effort to study the bristlefront in its scant Brazilian range. Now, those labors have paid off with an encounter with a chatty female bird, renewing scientists’ hopes that the species—and its extraordinary, endemic-rich habitat—is hanging on. Since the 1800s, the Stresemann’s Bristlefront has been an ornithological mystery. Only a few museum specimens have been collected from the seaside state of Bahia, Brazil, and wild sightings have been erratic, resulting in little information on the species’ behaviors and needs. The reason is twofold: On top of being rare and endemic, the bird is also extremely tough to detect. With its sooty and umber feathers and cryptic habits, the bristlefront is part of the hard-to-see, hard-to-ID tapaculo family...