If I remember correctly, it has something to do with nutrition, esp. while growing. Do you use medicated feed or feed the baby feed too long? I think you are only supposed to feed ducks the baby feed for a short time and then switch over or you have this problem... but it's been a few years since I was doing ducks... so my memory could be faulty.
-Bonnie

The tendency toward angel wing can be inherited, but it is generally believed to be caused by too much protein. I know little about ducks, but geese can get it too if fed too rich a diet. For geese, I have heard it recommended to replace the starter or grower with cracked corn and get them on good pasture. Caught early, it often corrects itself. The wing can also be bound into place for a time if necessary. If the diet is not corrected and the duck grows up that way, it will be permanent. It looks funny, but it is not a disease and the duck can still have a good life.

Genny, I suggest you google "treating angel wing ducks" or something like that to learn more.

Thanks Maggie and Megajas

I will read more about it. I fed them baby chicken starter feed as babies (same thing I have fed all my other ducks the last 4-5 yrs.) I don't feed them only that, but every few days I give them some and they love it! I've only ever had one duck to get this and she's a year old now, and like you said Maggie, she's living a normal life like the rest....but since it looks like so many babies are getting it right now I just wondered why. About 4-5 look like they have it :(