The Green-winged Teal looks very similar to the Eurasian Teal, but the vertical white bars on either side of the breast of the male are the key difference to look out for. It's much harder with the females, sometimes a rust-coloured wing bar is visible at the top of the speculum, but I don't think I'd be confident making the judgement!
|Green-winged Teal, ©David-Mitchell via Flickr Creative Commons.|
|Green-winged Teal sketch.|
This took longer than I had intended, so many spots, so much vermiculation....