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.”