Keeping birds out of your warehouse is a continuing problem unless you invest in long-term devices that are effective. Otherwise, the birds return once they learn it is "safe" again. Visual and auditory frightening devices can work at solving the immediate problem, but lose effectiveness once the birds get used to them. Scarecrows designed to mimic a bird's natural predator, like owls, snakes and coyotes won't work unless they look real and move. Auditory devices have the same limitations and only work if the sounds are diversified and moved periodically.
Evaluate the problem. Look at where the birds are roosting and building their nests. This helps you to decide which device works the best for that area.
Eliminate any sources of food and water that attract birds.
Block birds and bugs from entering with a flexible wall of 4- to 6-inch plastic or PVC strips. These inexpensive strips won't prevent people and vehicles from moving in and out of doorways. Strips also block out dirt, debris, rain and wind; they also help reduce heating and cooling costs by controlling air flow.
Install bird netting to prevent birds from reaching the rafters. Netting should be strong, lightweight, dark colored and have squares no larger than 3/4-inch square. According to Tom Barnes, an extension professor and extension wildlife specialist at the University of Kentucky, netting is one of the best solutions because it is an inexpensive long-term solution that won't affect ventilation. It also keeps out bats.
Coat roosting areas with a sticky or slippery substance designed to keep birds off. Birds avoid these substances because they don't like the feeling. After six months to a year, these substances no longer work because they have become coated with dirt or dust. Scrape off the old product with a putty knife and reapply for continued effectiveness.
Place porcupine-wire or spike systems on ledges and beams. The steel wires that extend in each direction don't harm the birds. They make it uncomfortable for birds to rest there. Aesthetically, these are one of the best systems because they blend in and are barely noticeable. But they are often expensive and labor-intensive to install.
Hire an electrician to install electrified wires. Electrified wires work the same way as porcupine-wire devices, but are used in very narrow areas. Don't try to install the devices yourself because they can present a fire hazard if not installed correctly.
Place monofilament lines about 1 to 2 feet apart in a grid like pattern. Grid systems are effective at repelling pigeons and sparrows, but may not work for persistent birds.
Poisoning or trapping native birds is prohibited by law.