Here are a couple of nice-looking useful and smart ways to re-use your old plastic bottles into bird-feeders:
1) For this one, apart from a large plastic bottle, you will also need two wooden spoons that work as actual feeders. The wholes above the spoons will let bird seeds out, but not too much:
2) I fell in love with this one: the roof looks fantastic! And your kids will love the idea of "Welcome home" message. It must really feel at home there: