That's the plan, Manheim Township manager Jim Martin said, to clear the pesky birds from their roosting areas.

"They're back where they have been the last few years," Martin said. "East of Park City Center, up to Granite Run and the big buildings there and northwest toward East Petersburg."

The township has joined with Wildlife Services, part of the U.S. Department of Agriculture's Animal and Plant Health Inspection Service, to try to disperse the birds.

The effort, which may continue through winter, also includes Lancaster city, East Hempfield Township, and East Petersburg Borough and private businesses.

Martin said Manheim Township's share of the cost is about $500 to $600.

As many as 20,000 crows roost in the area, officials said, causing a host of problems. The birds can cause major property damage by pecking holes in roofs, and their droppings can be a nuisance to passing vehicles.

Crow droppings also can contain salmonella, E. coli and other bacteria.

The first step in combatting the feathered invaders is to locate their main roosting sites.

Once that is accomplished, the township will use effigies of crow predators at sites easily visible to the birds. Cannon blasts and crow distress calls will be sounded in the hopes the birds will disperse.

Some crows will be trapped, banded and released. The tagged crows will be monitored to determine their flight patterns into and out of the roosting areas.

Martin said these techniques have proved effective in the past.

"It was pretty successful last year," he said.

If these efforts fail, the township and Wildlife Services will resort to using a poison known as DRC-1339 concentrate. A selective toxicant, it quickly affects crows and related birds such as pigeons, ravens and magpies, but has a minimal impact on songbirds, hawks and mammals, according to the township.

To minimize the effect on non-targeted birds, Wildlife Services would monitor the baited areas. Bait treated with DRC-1339 would not be left unattended, Martin said, and all unconsumed bait would be removed from the feeding sites each day.

The poison quickly degrades when exposed to moisture and sunlight, posing little threat to wildlife or domestic animals, officials said.

Because the poison is quickly digested by the crows, there is little risk of secondary contamination to scavengers feeding on crow carcasses.

Wildlife Services would collect the carcasses daily and ask the public to report dead crows to the township office for collection.