The morning air smells of balsam and wet duff as Adrienne Leppold sets out on a narrow trail to check the mist nets she set up before dawn to capture birds in a patch of forest in Orono. A great-crested flycatcher cries “wheep, WHEEP,” one of a dozen or so species calling and singing in the trees. Leppold doesn’t pause, however, to scan the branches. She makes a beeline for the nets, followed by three students she’s teaching the precise and delicate art of banding birds.