Birds that are looking for a dry, sheltered place to roost and lay eggs occasionally build nests around window air-conditioning units. These appliances appeal to birds because they offer protection from the elements and from predators. If you want to keep the birds out of your unit and away from your home, make your yard and air-conditioner less hospitable to them.
Remove any nesting materials left on or under your unit. Remove bird feeders, birdbaths or birdhouses from the area to avoid encouraging birds to consider your home a good habitat.
Place fake predators, such as plastic or inflatable owls or snakes, on or near the unit to discourage birds from returning to the area.
Wipe the unit down thoroughly with a strong-smelling cleaning product, such as bleach or vinegar, to further discourage birds. You also can spray the unit and the surrounding area with bird repellent.
Turn on the air-conditioning unit's fan and run it nonstop during the spring and summer when birds are nesting. They are less likely to roost on a running unit. In some parts of the country, you may have to run the unit year-round or remove it from your home and store in in a safe location when it is not in use.
Install grates, netting or or wire mesh around the air-conditioning unit to limit the birds' access.