Green-winged Teal are found across the Northern Hemisphere. Birds in the Old World, Common Teal, breed from Europe through Asia to the Aleutian Islands. New World birds, Green-winged Teal, are found across Alaska and Canada to many parts of the northern United States. The two populations are now considered to be races of the same species. This status may change, because genetic research shows that, although the races share one haplotype, they otherwise have very different mitochondrial DNA.
Since moving to Washington, Erika and I have searched for Common Teal. These ducks are of casual occurrence along both coasts of North America. We have scanned thousands of Green-wing Teal. On 1 March 2022 we met succeeded. Common Teal lack a white, verticle line behind their breasts. They have strong pale lines across the upper sides of their faces and under their eyes. Common Teal heads are slightly paler than those of Green-winged Teal. Perhaps the white patches on the back ends of Common Teal are a brighter white than the yellowish spots on Green-winged Teal. The sides of the Common Teal are more coarsely barred than on the American race. Our duck shows all these field marks. Less obvious is a white, horizontal stripe formed by the scapular feathers that should be obvious on Common Teals. Note that the scapulars on our duck are white-edged, not dark like on a Green-winged Teal. Not having this stripe apparent may indicate that this bird is a hybrid, but hybrids usually show the Green-wing’s vertical side stripe. Because of the preponderance of all the other field marks, we have no trouble calling this individual as a Common Teal.