We used to attract birds into or backyard by feeding them with f.i. peanut butter. The last years however, there is an outbreak of the black rat in our district. So we had to find a way of feeding the birds such that the rats can't reach the food.

The rats can climb in almost anything so there must be an obstacle that they can't pass. A way of doing this is creating a ceiling with edges that can't be reached by the rat. Even a rat has to deal with gravity. The construction should also prevent largers birds like doves or magpies to get into the house. Place it 1 meter away from higher bush/trees, otherwise the rat will be able to jump in.