Visual scare devices must be moved frequently so birds do not become accustomed to them. With scaring sounds, use mobile sound equipment so the location of the sound can be changed. When using automatic gas exploders, elevate them above the vegetation. Birds are more willing to leave a roost they have not been using long. After detecting large numbers of roosting birds, act as quickly as possible.
Some species are easier to move in the fall when they are restless and preparing to migrate.
Sometimes birds move to a new roost nearby and again several times within an urban area before they move to an acceptable site or out of town. In these situations, birds may become desensitized to scaring devices, so use several methods. Birds scare more easily when they are flying and are most difficult to scare when perched in the relative protection of their roost. Do not try to scare any longer because the birds will become accustomed to the sounds. When most of them are perched, play the call continuously until dark.