SAN FRANCISCO – They are as regular as hot dogs, Cracker Jack and the seventh inning stretch, after which they swarm like they're auditioning for a remake of Alfred Hitchcock's "The Birds."

Seagulls, ever-present visitors at AT&T Park, home to the Giants baseball team, are flocking in greater numbers this season. They swoop over the stands and even sometimes strut on the field during the last innings of games. One unfortunate gull collided with a high-speed pitch, a demise posted widely on the Internet.

"Sometimes it's uncomfortable," said Jorge Costa, senior vice president of ballpark operations. "They get too close. They've been somewhat aggressive and scared children and families."

No one is sure why the gulls are more plentiful this year. They present not just an annoyance, but also sanitation and health problems, said Costa, who's been fielding calls from people around the country with suggestions about how to get rid of them.

They've recommended spiking, netting, introducing natural predators and sound mitigation – all for a price. Ballpark officials already have tried what is technically called bioacoustics – broadcasting seagull distress calls – but the birds always come back.

"Birdcalls work for a while, but then they realize it's just a call and they ignore it," said Cheryl Strong, a wildlife biologist with the U.S. Fish and Wildlife Service.

Strong works with a San Francisco Bay restoration project where California gulls have been disturbing other nesting birds. As many as six varieties of gull might scavenge fast food and trash at the ballpark during the year, she said, and the California gull is the most aggressive.

"This is one of the few species of gulls that seems to do really well eating garbage, during the nesting season in particular," Strong said.

It is also a species that preys on the chicks of other birds. At the restoration project in the southern end of San Francisco Bay, wildlife experts braced for an influx of California gulls moving in after a salt pond hosting the Bay Area's largest colony of the hungry gulls was restored to tidal action to make the area more attractive to shorebirds. Not only were the gulls displaced, more shorebirds make more opportunity for the gulls.

Officials at the wildlife refuge, once home to a commercial salt-harvesting pond, have a limited arsenal for deterring gulls from nesting or eating other birds. Their strategies might also discourage the terns, avocets or endangered snowy plovers from taking up residence. Dogs, pyrotechnics and other predatory birds are not options, Strong said.

Instead, biologists relied on a human hazer, who walked into the wetlands twice a day blowing a whistle and waving her arms. It worked, at least temporarily.

Caitlin Robinson-Nilsen, director of the waterbird program at the San Francisco Bay Bird Observatory, who did the hazing, said there were 38,000 California gulls observed nesting in the South Bay this year, about 8,000 fewer than last year.

Some of the birds might have joined other colonies or gone farther inland, Robinson-Nilsen said, but they could be back next year. If so, biologists will be looking for new strategies.

Few entities are as vigilant about gull abatement as those handling sanitation and recycling. San Francisco-based Recology has tried noisemakers, falcons and large plastic windsocks.

"We used blowup things that looked like a 12-foot Gumby with arms that move," said company spokesman Robert Reed, describing attempts to scare gulls away from compost facilities in Solano County.

"It worked for a while, and then they figured out it was a windsock so we had to take it up a notch and go to a falconer," Reed said.

AT&T Park also is considering using a falconer next year, but hiring one is costly. Other methods – like blasting firecracker ammunition or shooting blanks overhead to discourage gulls, methods employed at the Miramar Landfill in San Diego – aren't likely to happen at the ballpark.

"We're continuing to evaluate things," said Costa, later adding, "Unless we go into postseason, (the gull issue) will die – the season will be over."

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Katherine Seligman is a San Francisco-based freelance writer.

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