The mess that the birds leave also is considered a health and sanitation issue for the borough, which has in the past used the fire department to hose the sidewalks down.
"Most towns on the East Coast have experienced the same problem. Every town around goes through this. Noise seems to be the most effective measure of getting rid of the birds," said Paul Cullinane Jr., executive director of Downtown Chambersburg Inc., who purchased the cannons.
The metallic devices connect to standard propane tanks commonly found on back yard gas grills. An electric ignition creates a spark that charges the gas built up in a chamber and lets out a loud, resonating sound, Cullinane explained.
As the birds fly in for the night, the cannons will be set off at both ends of the block on Main Street, between East Queen Street and the town square where the birds seem to be congregating most, and will then be moved up and down the street until the birds are gone, Cullinane said.
The cannons will be fired for about 20 minutes each night for between seven and 10 days.
"Our hope is to cause enough frustration that they just don't come back," Cullinane said. "We're looking for about an 80 percent success rate."
So far, the birds have ignored multiple eviction attempts by Cullinane, other borough officials and police who for the past three years have tried nearly everything to keep the birds out of the downtown trees.
The large trees sheltered by the buildings serve as the perfect protection for the flocks, especially in cold weather, Cullinane said.
Cullinane started out three years ago marching up and down the street for hours every night banging on tin cans with spoons to try to scare the birds away.
When the birds became wise to that tactic, Cullinane began climbing up into the trees, where he suspended plastic owls on poles. Balloons marked with scary faces were also tied to trees and buildings, but the birds were not deterred.
Other attempts to free the downtown of birds included turning on a high-frequency distress sound, thinning the trees and spraying a grape-flavored chemical that is supposed to cause upset stomachs in birds.
All attempts failed.
The latest technique - firing bird bangers and screamer sirens into the trees - works temporarily, but is labor- intensive and expensive, Cullinane said.
Three police officers are pulled from regular duty to fire the small explosives from handguns, while others stop traffic at the square.
Only three people, including one police officer, will operate the new cannons, he said.