The scientific name for the American Crow is Corvus brachyrhynchos. These crows increased in numbers since the implementation of the Migratory Bird Treaty Act, which was modified to include crows in 1972. The treaty makes it illegal to shoot crows. Individuals who have crows congregating on their roofs must find other methods of ridding themselves of these pests.
Mount a plastic owl on the roof where you see crows. This method of scaring the crows away will only work if you move the owl to a different location on your roof every couple of days. Otherwise, the crows will get use to seeing the owl in one spot and will cease to be scared of it.
Position a recorder on the roof and play distress calls. According to the University of Delaware, move the recorder every few days to continue deceiving the crows.
Let your pets loose in the yard. Train your dog to chase the crows that make their way on to your property, or let your cat do it, since cats are natural born hunters. If you don't have a dog or a cat, consider adopting one. The crows will get sick of being chased by the pets and your new dog or cat will by a companion for life..
Remove any food sources attracting the crows. Keep your pet food indoors, remove any bird feeders and keep mice and snakes off of your property.