JAMES WILEY says he doesn't hate pigeons, but that doesn't keep him from waging a full-time war against them.

Mr. Wiley, superintendent of stations for Metro-North Railroad, said that about 60 percent of 100 stations have a pigeon-prevention program. In 2002, the railroad began ''an all-out pigeon blitz'' at about 15 of the stations with the biggest pigeon infestations.

Standing in front of the Tarrytown train station last week, cradling a life-size Styrofoam pigeon covered in feathers that was sent as a demonstration tool from a bird-proofing company, Mr. Wiley was resigned about his continuing battle with pigeons. He pointed to walkways, peeling support beams and rusty trestles that had been newly lined with shiny metal spikes to keep pigeons from roosting on them, directly above areas where customers walk.

Mostly, the new system seems to work. A year ago, he said, pigeons were wriggling into stairwells and roosting above light fixtures that have since been removed. ''The pigeons were so brazen, they'd walk up the steps, right past the customers,'' he said.

Pigeon-related problems in Westchester are especially acute at train stations, shopping centers and tall buildings that have perches or ledges overhanging pedestrian walkways. Pest control companies agree that it is impossible to pigeon-proof a site. Instead, they try to relocate pigeons, persuading them to move over there from here.

Pigeons are sometimes called sky rats, and rightfully so, say pest control experts. Pigeon feces carry at least 36 diseases, some potentially fatal, including histoplasmosis and West Nile virus, and their droppings can accumulate into a dangerous and slippery mess, experts say.

''People are a lot more aware of the hazards of birds as disease carriers, and not as beautiful little creatures who happen to be infesting a building,'' said Greg Baumann, technical director of the National Pest Management Association in Virginia.

Nationwide, bird-control costs could exceed $100 million annually, with pigeons as ''the No.1 bird pest,'' Mr. Baumann said.

Since spring of 2002, Metro-North has spent about $150,000 a year on its pigeon eradication program, said Dan Brucker, a Metro-North spokesman.

Westchester's pigeon population may be nearly as bad as it is in New York City.

''The city's the city, but pigeons are everywhere,'' said Stuart Aust, owner of Bird Doctor, a pest control company headquartered in Paramus, N.J., that tries to curb nuisance birds in six states, including the New York metropolitan region.

Mr. Aust, whose company employs 40 people, said that he has many Westchester stores as clients, including Stop & Shop, BJ's and CVS and that the birds prefer to nest inside lighted signs that keep them warm in winter, particularly within the letters ''O,'' ''C'' and ''U.'' Mr. Aust said that after he treats a building for pigeon prevention -- using a number of things like wire mesh, nets, spikes and electric shocks -- he knows that the birds relocate nearby.

Indeed, many pigeon-proofing specialists are quite fond of the birds they displace.

''I love pigeons; they make me a lot of money,'' said Bruce Donoho, owner of Bird-B-Gone Inc., a company in Mission Viejo, Calif., that manufactures 100 different products used to fend off birds. Mr. Donoho said his bird spikes and other systems are used on the Brooklyn Bridge, at Ellis Island and at Metro-North stations.

''Pigeons are very stubborn birds,'' he said. ''Once they nest in an area, they tend to nest there generation upon generation, and they can multiply two or three times a year.''

Of the 15 or so Westchester train stations with severe pigeon problems, the ones where Metro-North did the most work trying to keep the pigeons out were the stations in Yonkers, White Plains, Croton-Harmon, Tarrytown, Port Chester, Rye and Ossining, Mr. Brucker said. The larger the station, the more severe the problem because there are more places for pigeons to nest.

Mr. Brucker said that getting rid of the birds ''is not easy and it is frustrating, and at best you are relocating them.'' Since 2002, workers have installed ''little metal fingers that stand up,'' to keep birds from roosting, as well as tinglers, a wire that gives perching pigeons a low voltage shock. Early on, he said, the railroad discovered that plastic owls do not work, because ''the pigeons simply roost on top of them.''

Perhaps the most creative method to get rid of pigeons was tried at the Fordham and Ossining train stations.

''We played diurnal recordings of predator birds, like falcons and hawks,'' Mr. Brucker said. The loud shrieks effectively scared off pigeons, he said, but also terrified commuters. ''Customers would hear the excellent high-fidelity recordings and cower down, thinking that a bird was swooping in on them, so we stopped using it in Ossining,'' he said.

INTERESTINGLY enough, at the Fordham station in the Bronx, no one seemed to notice the noise. ''They were more stoic to falcons and hawks,'' Mr. Brucker said.

This year, because of cutbacks, Metro-North's pigeon-proofing budget has been reduced to $50,000, Mr. Brucker said.

That setback is being offset, however, by the railroad's renovation of stations, which requires contractors to have pigeon-proofing plans, Mr. Wiley said. When the Tarrytown station is renovated, beginning in 2007, he said, an elaborate system of mesh netting will prevent pigeons from moving in.

While Metro-North installs all of its own antipigeon devices, other pigeon-plagued businesses in Westchester have hired pest removal services.

BirdMaster, a Woburn, Mass., company specializing in historic preservation, has chased pigeons from the Statue of Liberty, the Metropolitan Museum of Art and the Washington Square Arch in Greenwich Village, and was recently selected to take on the pigeons at the Capitol building in Washington. ''It's a real feather in our cap,'' Mr. Pace said, with no apparent tongue in cheek.

In 2002, the company took on the pigeon-infested Hudson Valley Writers' Center, housed in the Philipse Manor train station. The company covered nearly every square inch of the corners, cornices and niches at the center with plastic mesh netting. The job cost about $8,000, said Maureen Hatch, associate director of the center.

''We had pigeons all over the roof, and they had babies, and there was pigeon poop everywhere,'' Ms. Hatch said. ''They're homing pigeons and they're home and they can't go anywhere else.'' Since BirdMaster completed the job, however, the pigeons have found new homes, she said.

But outspoken pigeon advocates don't blame the birds for the problems. ''Pigeons are persistent, rather like people, and they want to find a place to live,'' said Charles Walcott, a neurobiology professor at Cornell University who was director of the bird laboratories there for 14 years.

Mr. Walcott once kept about 1,000 homing pigeons, which he called ''the athletes of the pigeon world,'' for research purposes, before the university closed his pigeon loft, saying they had to be housed in individual, cages, and not in a large coop. But pigeons would suffer if put in single cages, Mr. Walcott said, so he disbanded his flock.

As for keeping pigeons from roosting where they aren't wanted, ''pigeons do have great site fidelity,'' he said, ''and they return to the same area where they were born. But if you make it impossible, they go somewhere else, and the neighbors will inherit your pigeon problem.''