Cool! (Just to be clear, I meant the common, or Eurasian, teal whose iridescent green head markings the color’s apparently named after. The NA teals are closely related, although it seems they were assigned to their own genus in 2009 as it was discovered that the then-Anas was not monophyletic.)

Generally colors are named after things in nature and not the other way around, given that the latter would’be had names for a long time, and most color names are comparatively recent inventions, driven by modern dyes and pigments and status, fashion, etc concerns. A West European peasant in the 11th century would’ve known the bird well, possibly trapped them for food, but would’ve had very little need for a separate word for ”blue-green”.

The history of color words is quite interesting. There’s a specific progression that almost all languages have gone through. It’s fairly well known that many East Asian languages don’t have separate names for ”blue” and ”green” at all (except as modern loans). Accordingly, they don’t usually make the distinction mentally, one could think that they simply consider them hues of ”cyan”.