Is this common Raven behaviour, washing the nesting material? The bird would drop the material into the water, poke around at it, lift it out, drop it again and repeat the process a couple of time before flying off with it. The process was then repeated with another new lot of bark. I can only assume it was softening the fibers before using them in the nest. Any other ideas? The image was taken through double glazed glass so is not very good.

Washing Nesting Material by Brigitte D, on Flickr