Recently, I got a call from a woman who said that a 92-year-old member of her church had been keeping himself occupied by building birdhouses. She said he had made - are you ready for this? - 1,000 so far. She wanted to know if I could help find a way to distribute these houses to people who would use them. I went to the church and looked at a sample house. It was made of rustic, unpainted cedar (good), but the holes were too big and not spaced correctly. These houses would be perfect for the two invaders - House Sparrows and Starlings. If a native bird, such as a Tree Swallow or Bluebird, were to find one of these boxes hanging on a post and move in with the intention of starting a family, they would be at high risk of having a sparrow or starling find them, kill them, throw their eggs or babies out, and take over the box. Nesting failure is high enough without us contributing to it by putting up the wrong type of boxes.
A birdhouse has to be made to the correct specifications for whatever bird you are designing it for. Building and putting up a birdhouse can be really fun - especially if you do it with a child, giving you both something to watch and share as the birds move in and nest. But it is wise to do a little figuring first. Do you live beside a big weedy open area, such as a farm or a field? You could make a bluebird or tree swallow box. Do you live in a city in the western US, but have eaves under your roof? Make a Violet-green Swallow box. If you have a woodsy area nearby, you could make a Chickadee or Nuthatch box and nail it to a dead stump.
And about the 1,000 birdhouses? My Audubon group decided to take 100 of them and do a little sawing and repositioning, and make them into Chickadee boxes. It's one of our projects for the summer.
Here are some plans that have all the right dimensions:
More Birdhouse Specs