Goose acrobatics

I was at Potteric Carr today watching a party of greylags on one of the lakes. One was up-ending and then appeared to overbalance and thus finish up on its back with its legs waving in the air. After much spalshing, it righted itself.

At first I thought this was just an incompetent bird who had not quite got feeding sorted but, as I watched, it did the same thing a few more times and appeared to be preening - it looked as if the bird was actually having a bath and deliberately doing forward rolls!

Has anyone seen this sort of behaviour before?

There were quite a few greylags about - the photo is of a bird grazing just outside the hide - I was actually trying to photograph some hares in the same field, one of which still had traces of its winter coat, but they were moving far to fast! Great to see them though.