As Stefanie Boss and her husband, Mike Reed, walk down Smoke-town Road on the Antietam National Battlefield property, a bird with bright blue feathers, a rusty-colored breast, and white belly darts from its perch on the wooden fence to the nearby trees.

High up on the Appalachian Trail is a non-descript little hut that is key to helping scientists learn the habits of the elusive saw-whet owl. This tiniest of owls, about the size of a robin except much more stout, migrates south each fall. Saw-whet owls have several migration routes, one following the South Mountain corridor. These nocturnal creatures often fly through rural areas where they can seek cover in evergreen forests.