For Pigeons, first see if someone in the neighborhood is raising or feeding Pigeons. If so, you may be able to talk to the person and persuade him or her to stop.

Roosting is difficult to control. Sometimes models of a predator - rubber snakes and plastic owls - dissuade Pigeons, but often they just get used to them. Nixalite, a metal stripping with upright spikes, may be placed along sills and roof peaks. Information can be obtained from the manufacturer: the Nixalite Co. of America, 417 25th street, Moline, IL 61265.

For gulls, a single strand of wire strung six inches above the roof ridge may discourage them.