Nasal leeches

Bloodsucking leeches of the genus Theromyzon sp. are the only leeches in North America known to feed directly in the nasal passages, trachea, and beneath the nictitating membrane of the eyes of migratory birds. Three species of nasal leeches have been reported from North America, T. rude, T. tessulatum, and T. biannulatum. Other genera of leeches feed on the exposed surfaces of waterfowl.