US Fish & Wildlife Service


Date of this Version

January 1989


Published in Diana H. Cross and Paul Vohs (eds.) Waterfowl Management Handbook. Fort Collins, CO: U.S. Fish and Wildlife Service, 1988. Online at


Avian botulism is a paralytic, often fatal disease of birds resulting from ingestion of toxin produced by the bacterium Clostridium botulinum. Waterfowl die-offs from the botulism are usually caused by type C toxin; sporadic die-offs among fish-eating birds, such as common loons (Gavia immer) and gulls, have been caused by type E toxin.

Not enough is known about avian botulism to precisely identify the factors leading to an outbreak. When an outbreak does occur, it is usually perpetuated by a well-understood bird-maggot cycle (Figure 1).