A book of questions, theories, and answers—all the more intriguing for being partial—Ackerman’s compelling third study of birds could as well be titled “What Humans Don’t Know about Owls But are Determined to Find Out.” Each of the thematic chapters delves into a basic “how” of owl life—from courting, mating, and breeding to migrating, hunting, feeding, nesting, and perceiving the world—and explores how different species have adapted to their particular niches. A burrowing owl will collect (or hoard?) a wide range of colorful, often man-made objects to decorate its underground nest, for instance. A saw-whet owl is so “cryptic” it can stay invisible even as it calls from a tree beside you. And urban owlets practice hunting by raiding clothes lines. But owl behavior is just half of Ackerman’s story. She also introduces the many, equally fascinating humans who study these creatures, reporting on the awe and wonder that drew them to the woods in the first place and that—literally—keeps them up nights listening to calls, searching high and low for elusive nests, counting and banding birds, and solving one mystery with the discovery of several more.