Preliminary tests have found avian botulism to be the cause of death of waterfowl at Smith and Bybee Wetlands Natural Area.
Metro collaborated with Oregon Department of Fish and Wildlife to collect more than a dozen birds for testing at the Oregon State University Veterinary Diagnostic Lab and the National Wildlife Health Center Lab in Madison, Wis. The center is one of the few labs that can test for avian botulism and their preliminary results found botulism to be the cause of the die-off.
The botulism bacteria is widespread in soil and requires warm temperatures, organic matter and an anaerobic (no oxygen) environment in order to become active and produce toxin. It is typically spread when birds eat maggots that carry the toxin. Also called "limberneck," the birds are unable to lift their neck and many drown. The National Wildlife Health Center has more information on avian botulism.
Metro and Oregon Department of Fish and Wildlife staff have removed more than 1,200 dead or dying birds to date, mostly migrating waterfowl. Several shorebirds and a pelican also died. Portland Audubon has been receiving and rehabilitating live affected birds which will be released when they have recovered and are able to continue their migration. All of these populations are healthy and impacts to overall bird populations from this incident will be minor.
The area has been closed since Friday, Sept.7. There is very low public health risk due to avian botulism; however, the area will remain closed to paddlers until the outbreak ends.