I thought I had found a female American Wigeon this morning – I knew there were two types of female Eurasian Wigeon – rufous and grey – but it wasn’t until I got home that I found (courtesy of Steve Madge) that there was an intermediate between the two – now I am not so sure.

Lol, looks like Eurasian to me, but as I’m sure you know the underwing is what you need to see well
As you say Barry – the white auxiliaries are the key separation feature – and getting them to fly is tricky 😉