Here is a bat inspection in Weston, CT and it shows evidence of a major bat problem.
Pictured is bat guano. This customer had over 150 brown bats living in her attic.
The presence of bats can be detected in several ways. At dusk, when bats leave roosts to feed, they may be seen exiting through eaves, vents or from behind shutters or siding. Noise from large colonies may also announce their presence. Droppings and dark brown stains may appear near eaves and beneath entrance holes and roosts. Bat droppings (guano) are easily crushed, revealing shiny bits of undigested insects. They are never white or chalky in appearance, as are the droppings of birds.
The 2 most common bats involved in nuisance complaints are the little brown bat and the big brown bat.
When guano is disturbed it can cause health hazards, including histoplasmosis, a fungal disease associated with the droppings of birds and bats, can result from the disturbance of dried droppings. Disturbance causes the fungal spores to become airborne, and spores entering the lungs can cause respiratory problems.
Another reason why a bat inspection is so important to determine how big of a bat issue you may be experiencing.