Generally more northern than the closely related yellow-billed, black-billeds can be found in deciduous woodlands where there are caterpillars. During outbreaks of tent caterpillars both species can be locally common. Like the other cuckoos, it has a slow, almost floppy flight as it moves from tree to tree. The black-billed cuckoo is separated from the yellow-billed by its all-black bill, lack of rufous in the wings, and muted undertail pattern, which barely shows contrast between the gray and white spots. The common call is a long soft series of cu notes, all at the same speed and pitch.
Hear the black-billed cuckoo: