Birds such as sparrows and starlings sometimes build their nests in buildings, including houses. Some of their favorite nesting sites include under niches, such as a building's eaves, and in or near the exterior vents of dryers, stoves and bathroom exhausts. Their nesting material can clog vents, block air flow and result in a buildup of carbon monoxide. The birds can also accidentally puncture the exhaust vent pipe while building their nest. This can cause a building's interior to harbor mold, as moisture from the bathroom escapes into the ceilings and walls. Birds residing in bathroom exhausts also pose a health hazard. They can spread bird mites, lice and diseases such as histoplasmosis and salmonella. To rid bathroom exhausts of birds, combine humane removal measures with "exclusion tactics" -- actions that will prevent future bird nesting.
Examine the bathroom vent for signs of eggs or chicks in the nest. If you observe eggs or chicks, you must leave the nest undisturbed until the baby birds mature and leave the nest. If you don't see or hear the chicks chirping loudly for food during the day, or observe a parent bird entering or exiting the bathroom vent for several hours, you can assume the nest is empty.
Remove nesting material that is within your reach with a wire coat hanger. Use a garden hose to push out excess nesting material. Pass the hose from the inside of your house through the exhaust vent hose until it appears through the exterior vent, pushing out nesting material and debris as the hose moves through the exhaust.
Apply a disinfectant to the exterior vent area after you have removed all the nesting material. Clean the area surrounding the vent thoroughly to prevent the spread of bird-related diseases.
Install exclusion devices such as vent covers, bird netting or bird spikes around the exterior of your exhaust. These devices will prevent birds from entering your bathroom exhaust.