One influenza-A virus isolated from domestic turkeys in California [USA] in 1964 and 2 from migrating ducks in Delaware in 1973 were classified as Hav6 and Nav5, i.e., antigenically the same as A/Shearwater/Australia/1/72. The detection of antigenically related viruses in 3 different species over a 10-yr period suggests a broad host range, contributing to continued circulation in nature. The turkeys suffered severe respiratory disease although infected migratory birds did not reveal signs of disease. These results suggest migratory birds, which travel over vast areas, as a source of influenza viruses infecting domestic species.