It is a perennial late-game conversation starter at Giants home games: “How do the gulls know to swarm to the ballpark during the ninth inning?”
But for team administrators, the flocks of trash-seeking birds are less an enigma than a serious nuisance that has been escalating since the waterfront ballpark opened in 2000.
This season, the Western gulls, which nest on Alcatraz and other nearby shorelines, have been swooping into stands even earlier, gobbling up dropped fries, soiling fans and prompting officials to consider using falcons to chase them away.
“We’ve seen an increase in the birds,” said Jorge Costa, the Giants’ operations manager, “and the behavior seems to be more aggressive. They’ve started flying around and trying to go into the stands while the game’s still in progress. That’s unusual for them.”
During some recent games, the avian avalanche has begun during the seventh-inning stretch, according to Costa.
The hefty birds possess keen vision and hearing, said Dan Murphy, a Giants fan and Golden Gate Audubon volunteer.
“They probably see the lights on, or in the afternoon they probably see the crowd,” Murphy said. “As the crowd starts thinning, they just show up.”
Murphy and other bird experts said the Bay Area population of thousands of native Western gulls had not grown recently, which suggests that it is changes in the birds’ behavior that are worsening the Giants’ sea gull predicament.
“Gulls here in the Bay Area are very used to human activity,” Caitlin Robinson-Nilsen, a San Francisco Bay Bird Observatory water-bird expert, said. “They may have learned that if they can put up with the additional human activity of all the people who stay through the ninth, then there is more food available to them.”
The Bay Area’s Western gulls notoriously devour trash as part of a diet that also includes eggs, other birds, fish, small mammals and roadkill.
Recology, the trash hauling and management company, also has a gull problem at its southern San Francisco waste transfer facility, which it has addressed using Wingmaster Falconry Inc.
The Giants are considering hiring the same company to deploy trained falcons or hawks at the ballpark during games, Costa said. He said the team is also investigating whether it can attract a pair of peregrine falcons to nest at the ballpark.
Falconry is a hunting sport that normally involves hungry raptors. Commercial falconers, however, use well-fed hawks and falcons to frighten birds away from airports, dumps and farms, not kill them.
Several falconers could be used at Giants home games, and the team plans to decide in the coming months whether it would be worth spending up to the $100,000 — and perhaps even more — needed annually for the effort.
“There’s a natural predator-prey relationship,” Steven Vasconcellos, Wingmaster Falconry’s president, said. “You can fly your hawk, scare away the pest species and get the job done without there being corpses laying around.”
This article also appears in the Bay Area edition of The New York Times.