Bat House Color Recommendations and
Average Daily High Temperatures in July
Dark blue - less than 85°F. recommend black paint, black roof
Light blue - 85°-95° F. recommend dark shade of paint, black roof
Dark red - 95°-100° F. recommend medium shade of paint, white roof
Light red - 100° F. or greater, recommend light shade of paint, white roof
TEMPERATURE IS A CRITICAL FACTOR in determining bat house use. While northern bats often need considerable heating in their roosts, southern bats, especially in lowland desert areas, may need much less. By taking advantage of solar heating you can significantly alter the temperature in your bat house. The amount of sun exposure needed will vary with local climates.
In middle and northern latitudes bat houses should receive at least six hours of daily sun, preferably 8-12 hours. Additional measures can be taken to enhance the effects of solar heating. Contrary to previously published information, painting or staining the outside of your bat house can actually increase the chances of attracting bats. Once thought to repel bats due to odor, dark brown or black paint or stain on the exterior of bat houses in the North increases the temperature in the house. Carefully caulk all exterior joints before painting.
Similarly, light colors may reflect nearly all solar heat on bat houses in southern latitudes, thus allowing exposure to more sun without overheating. In the South, houses should be painted or stained medium to dark brown or, in exceptionally hot areas, light brown. In all but the hottest desert areas, they should still receive at least six hours of sun, particularly morning sun. It is easier to attract bats in southern areas if two houses are mounted back-to-back on poles, facing north and south, with a 3/4" space between. This way the bats will be able to move back and forth to seek the optimum temperature. In the hottest areas, houses can be partially shaded by an overhanging tin roof that protects them from the day's hottest sun. If you observe bats constantly occupying the lowest portions of the bat box, it is probably too hot or overcrowded.
No matter what part of the country you live in, exposure to sun and proper color are critically important to success.
These installation directions are specifically for attracting little brown and Indiana bats to bat boxes where the average summer daytime temperature is below 95° F. For warmer areas a special white-roof BCM bat house kit can be ordered. Other Pennsylvania species known to have used BCM bat houses are big brown and Northern long-eared bats but their temperature preferences are not well understood. We at BCM suspect our box will be successfull in all parts of the world with any bat species with similar temperature and roost preferences.
Will a bat house in your area attract bats? Bats are constantly on the prowl for suitable alternate roosts. If a bats can be seen occasionally at dusk, then likely the area should support a new bat house. Having a known roost nearby is even better, but be aware that bats will not abandon The box should be placed at least ten feet above the ground in an open area orientated south-southeast (135° azimuth is optimal) where it receives at least seven hours of direct sun. If the box is to be used to help evict bats from a structure, then ideally the box should be placed on the structure itself. It is also ideal to have the box near the bat's entrance into the structure. However, seven hours of direct morning sunlight is of paramount importance and outweighs all other factors. After the second year of occupation, the box may be moved off the structure and onto a pole several hundred feet away. Box disturbance during the inital summer may cause bats to abandon the box.
The box will be more attractive to bats if it is within 1,500 feet of a permanent stream or pond. Bats need a drink on very hot summer days, and the fresh water guarantees a nearby feeding zone.
Habitat diversity will also attract bats. A combination of forests, clearings, and wetlands will produce different types of insect activity at different times throughout the summer, assuring a constant supply of food. The box should be within 10-30 yards of a tree line to provide quick cover from predators, such as owls. If there is an existing roost nearby, the bats may not move into the box unless something happens to the existing roost (i.e. it becomes sealed).