We have an owl that sits somewhere in our garden at night. He screeches and "twoo's", but never seems to "twit". From looking at bird books etc I think that it may be a tawny owl, but as my garden has lots of trees for him to hide in I've never seen him. However, I did spot an owl in a tree futher down the road when coming home late one evening and got very excited! OH thought I was mad!