The chickadee-dee-dee mobbing alarm calls of black-capped chickadees contain messages—coded in the number of dees at the end of the call—about the size of a predator and hence, the degree of threat it represents. More dees means a smaller, more dangerous predator. A great horned owl, too big and clumsy to pose much of a risk to the tiny chickadee, elicits only a few dees, while a small, agile bird of prey such as a merlin or a northern pygmy owl may draw a long string of up to twelve dees.
