State and federal officials say a fungus infection, not avian influenza, killed 2,500 mallards in Idaho. Symptoms of the birds were not consistent with avian influenza, and samples tested negative for the H5N1 strain of avian influenza.
Officials think the birds were sickened as a result of eating moldy corn, although no specific corn has been found. After becoming infected by aspergillosis spores, which officials believe came from a single contamination source, the birds gathered at a roosting point and died.
Officials said from the beginning of the investigation that bird flu was not likely to have caused the die-off.