Current bat house designs were developed to accommodate bats living in north temperate regions of North America and Europe. Most are intended to appeal to as many species as possible, instead of accommodating the specific needs of any one. Nearly all bat boxes currently used in the U.S. and Canada are designed to accommodate bats that roost in tight crevices, in part because crevice roosters are those most often encountered in urban areas. Other species prefer open ceilings, allowing them to form clusters. Many European bat boxes cater to these, though most such boxes are still quite small.
Bats sometimes use bluebird houses as temporary roosts as well.
On a 73 box trail in Illinois, bats occupied seven of the boxes from early September until mid-October. The use of bluebird boxes by bats may be more frequent than known, since most observers are not trained to identify bat droppings. Learning what bats need Nearly half the bat species in the United States and Canada are of the type that could conceivably occupy artificial roosts. Greater knowledge of their roosting preferences is urgently needed as many bats are rapidly losing their traditional roosts. Old trees that provided bats with loose bark or hollow interiors are being lost to modern forestry practices and urbanization.