Observe the sizes given for the entrance holes and use them. While birds may nest in houses with larger holes, competitors or enemies may also be able to enter. For example, if you make the hole in a bluebird house 1% to 2 inches in diameter, starlings will enter and displace or fight with the bluebirds or even usurp the nest. If it is 11/2 inches, these slum-children of the bird-world will be excluded. Similar considerations have brought about the choice of sizes for the entrance holes for all birds.

Some species have more than one nesting each season, and each nesting requires a new nest. If all the old material is cleaned out after the fledglings of the first brood have departed, it is quite possible that the house will be used for the second nesting. The cleanouts spoken of previously will facilitate cleaning. If you have woodpeckers, they will appreciate 2 inches of sawdust placed loosely in the bottom of their box nests. They seem to require it for their nest, probably because they are used to having wood chips or rotting wood in the natural nesting cavities in dead trees in the woods.

As indicated in our plans, entrance holes are placed high so that the mother bird is concealed when she is sitting on the nest. Holes must not be placed lower or higher (this latter will make it difficult for the bird to enter), but at the position indicated. A natural twig or a dowel placed in a hole on the front of the house will give birds an alighting place from which they can hop up into the entrance hole. Some bird observers claim that robins need a good-sized branch extending out and below the shelter, stating that robins like to alight and walk up to the nest. This theory would seem to be borne out by the fact that robins like to nest on flat limbs in orchards.