Fowl seek homes to raise families

When it comes to birdhouses, size matters, especially the size of the entrance hole. If you are trying to attract particular species to your yard, make sure to make the entrance hole just big enough for the desired birds to enter but not too big or else larger species will move in and evict your target bird. If you are looking to attract bluebirds, for instance, the hole should be 1.5 inches in diameter, while the entrance for a house for chickadees should be 1.125 inches and 1.25 inches for wrens.
Proper habitat is also key. If you don’t have a large meadow-like opening in your yard, it is unlikely you will attract bluebirds, which prefer to nest where it is wide open. Chickadees, nuthatches and titmice prefer to nest at the forest edge while wrens are well adapted to suburban yards.
It is vital that your birdhouse have a panel that can be opened. Birdhouses should be cleaned of last year’s nest every winter because many birds will not nest in a house that already has a nest in it. If you can’t open the house to clean out the old nest, then the house is only useful for one nesting season. I clean my birdhouses in late winter just before the nesting season begins. 
One reason for cleaning my houses at that time is that it enables mice, flying squirrels and other creatures to use the house as a winter home. More often than not when I open my birdhouses for cleaning, the box is filled with nesting material, with a mouse or two huddled beneath it. If you wait until spring to clean the houses, the mice will often have begun raising their own litters. If that’s the case, I leave them be even though I know that no bird will nest there that year.
When I maintained a five-mile long trail of 50 bluebird houses along the power line corridors in northern Rhode Island in the 1990s, dozens of mice leaped out at me as I cleaned out the birdhouses each winter. The first time it happened was quite a shock, but after a while I grew to enjoy those encounters, and I learned to appreciate the ability of mice to thrive during chilly winters.
Finally, remember that a birdhouse is an artificial tree cavity, and only cavity-nesting birds will move in to raise a family. Most of our backyard birds -- robins, cardinals, doves, sparrows, warblers and hummingbirds -- build open-cup nests on the branches of trees and shrubs and will never enter a birdhouse or tree cavity. But those that use a cavity will appreciate your effort to provide them with a home.
 
Todd McLeish is a science writer at the University of Rhode Island and a lifelong birdwatcher. Contact him at tmcleish@uri.edu.