If it were me, I’d wait a few days to see if it corrects itself. Some wing droopiness is normal, especially when the feathers first start coming in. If not,then I'd tape the wings and hopefully that will correct the issue. But I would not use that particular duck for breeding.
I dealt with angel wing in one of my goslings last year and even with taping the wings (3 times no less) the problem was never fully fixed. When I asked for advice from waterfowl experts I was told this:
It's not necessarily just too much protein, but a combination of too much protein, too much sugar and not enough manganese? (I think. Sorry it's early.) But here's the funny part of the situation- you can have 10 goslings eating the same feed and only 1 ends up with angel wing. So how come only 1 got it and the rest are fine? Why are Africans more prone to it than Toulouses? There is a hypothesis that angel wing is in fact a genetic condition with a dietary trigger. If you believe that then angel wing could be eliminated in geese by selective breeding- culling out any birds with signs of it. If you remove birds with the defective genes it theoretically shouldn't matter what you feed your birds. They will not have the condition.
In the end, without further research nobody truly knows what causes angel wing.
Good luck with your ducky.
