A drey — or dray — is a nest of a tree squirrel or a flying squirrel. Dreys are usually built of twigs, dry leaves, and grass, and typically assembled in the forks of a tall tree.They are sometimes referred to as “drey nests” to distinguish them from squirrel “cavity nests” (also termed “dens”). drey is almost always at least 20 feet (6.1 m) above the ground, and flying squirrels build much higher. Sometimes squirrels build their own dreys and sometimes they occupy a vacant drey that was previously constructed by another tree squirrel, often of a different species.