I'd have to search for the pictures I took but I saw crows roosting in the woods between my house and the campus of Notre Dame. There was a path through the woods and I commuted on foot. It was March so no leaves on the trees but there were so many crows it LOOKED like the trees were completely leafed out. It was really amazing but just a bit creepy when the birds went completely silent as I walked past then started up behind me. Like a typical human idiot I always said hello and that I wasn't a threat to them--I think it just felt rude not to. I've never seen that behavior before of since but that's when my fascination with crows started.