Wing Droop Dance?

[alEkat]

Does anyone know what this behavior is called? (Video link to YouTube at bottom) I'm trying to do more research on it but I dont know what to look up.
Their wings drop up and down, usually alternating each side. They've done it while grooming, almost like it is a compulsion.
Most of our flock does it and it doesnt seem to be weather related; I've seen them do it in the winter and the summer.
Our flock mainly consists of Chinese/African but we have some Buffs, Romans, and Sebastopols.
Does anyone know what it is called and/or why they do it?

Thanks

 

[Goosebaby]

I think it’s a way of airing out their under wing feathers to dry out.

 

[Jenbirdee]

yes I agree what @Goosebaby said i think that too I have seen a couple of my ducks doing it

 

[JRies]

There preening and showing off a bit. They can only get there gland oil;s applied to spots they need a way to spread them to be waterproof. So fun to watch. Thank You.