h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

They're really bad.
Either the soft tap-tapping of a branch against a window or the strange creaking they make that sounds like they're going to fall down.....argh. Thank goodness the cacophany of the city means you cannot hear the trees coming for you .

Also - if you're out in the countryside in a farming area (like, say Sligo ) then at about 4am a calf and her mother will suddenly find themsleves on different sides of a hedge or fence. The resultant cries of alarm usually convince you (against the more sensible side of your mind) that there are large cow eating animals on the loose...