Herds of ducks

There is a creek very close to our house, so we tend to get a lot of creek-loving animals like ducks, herons and raccoons around our place.
Although we've lived here for over 2 years now, I've never seen the ducks do this before:
They come in these big groups of maybe 15 and go all crazy trying to find as many acorns off the ground as they can and swallow them whole. Very weird.

-Andrea