Eurasian Green-Winged Teal

The green-winged teal or American green-winged teal is treated as the same species as the Eurasian green-winged teal by Birds of the World. They are treated as separate species by iNaturalist and Wikipedia, the two other sources I usually look at. Wikipedia notes that whether they are one or two species is still being reviewed by the American Ornithologists Union while the International Union for the Conservation of Nature and Birdlife International treat them as separate species. 

I saw my first Eurasian green-winged teals in Kaziranga NP in Assam, India in December 2024. They were at some distance from our vehicle in a lake surrounded by other kinds of ducks in the Eastern Range. 

Since I only saw, or at least only photographed the more colorful males, I show illustrations of the male Eurasian green-winged teal from Birds of the World, one standing and one flying. 

Next I show the illustration of a standing green-winged teal or American green-winged teal from Birds of the World. 

The most obvious differences are that the breast of the American is darker than the Eurasian, the American has a vertical white line on the side that the Eurasian does not have, and the Eurasian has a white and black line at the outer edge of the secondary feathers while the American has only a black line. Below are two photos of American green-winged teals I took in Newport Bay. These photos clearly show the vertical white line on the side that they Eurasians do not have and they show the lighter belly which looks like the belly on the Eurasian teal and not the American teal. 

This photo taken at the Leona Turnbill Birding Center in Port Aransas, Texas have a little more colorful chest and breast, but not as dark as the illustration has. So it appears that the vertical line on the side may be the best indicator, other than, of course, geography. Below is the range of the Eurasian green-winged teal from Wikipedia (the range map from Birds of the World includes the American green-winged teal as well). Assam, India is clearly where they are wintering.