I have, was on my merry way to bleakfalls barrow and as i crossed the bridge the only thing that could describe the noise i heard is if someone detonated a bomb,
a bomb mate out of sparrows..that fractures into smaller sparrows...
Playing with headphones on high volume it kinda freaked me out, so when i was done [censored]ting myself i decided to find the birdbomb and narrowed it down to a small pine tree close by and found this:
http://steamcommunity.com/profiles/76561198052078653/screenshot/595827796553851752
http://steamcommunity.com/profiles/76561198052078653/screenshot/595827796554953699
If you have trouble seeing it, it's a lota' birds stuck in a tree. Nice, made me smile.

I had to switch to a different arrow type to get them back.