Biologists suspected avian cholera because outbreaks of avian cholera are common among snow geese during spring migrations. At least one bird examined in the field showed symptoms consistent with cholera. 24 birds were randomly selected and sent to the Idaho Fish and Game Wildlife Health Lab for further testing. The rest were incinerated to prevent ingestion by scavengers.
Lab results were inconclusive for avian cholera but indicated some of the tested birds died from zinc phosphide poisoning. Zinc phosphide is a compound used in rodenticides to control voles and other rodents that damage crops. Avian cholera may have played a part in the die off but to what extent is unknown.
Idaho Fish and Game has provided the lab results to the Idaho Department of Agriculture. It is important to stress that while unfortunate, the die off will not affect overall snow goose populations, which number in the millions.