This is the teapot (1.50 €) I bought at the second hand shop. Although I would have preferred a more kitsch one with some gold and flowers this was the only one they had. In the end it did not even turn out to be such a bad choice.
When I finally figured out how to operate my Christmas present Dremel (thanks Tom < 3) I drilled a hole in the bottom with a diamond bit. At first the drilling didn't go so well (it sounded like the dentist), but then I remembered reading somewhere that you should add a little water to the porcelain surface you are drilling, and it flew through.
At around 2.5 m we had a lonely and useless peg in the wall outside that looked perfect for the new birdhouse. With a little wiggling and enlarging the hole it even fit! And look how cute it is (the fake bird (aka geocache) for the pictures was Toms brilliant idea)!!!