The answer is.... Drake.

No doubt about it. Just as annoying as greylings and greydwarf, but they have that horrible shriek. They do no real damage, but they knock you around so, between that and that shriek you can't just ignore them for long.

You can't just swat them like you do greydwarf either. You can to pull out your bow, wait for them to come into view, and then finally shut them up, but not without one last shriek!

Then the next one comes by...