California has a problem: Gulls gone wild

Seagulls fly over AT&T Park during the ninth inning of a semifinal game of the World Baseball Classic between the Netherlands and the Dominican Republic in San Francisco, Monday, March 18, 2013.

An exploding seagull population in California's Bay Area is wreaking havoc, terrorizing airports, landfills and other protected birds.

In the San Francisco Bay Area, not far from where Alfred Hitchcock’s "The Birds" was filmed, the seagull population is exploding, and no one can figure out why, or how to stop it. 

Just a few decades ago, the California gull population was so low it was listed as a California "Species of Special Concern," due to its limited range and dwindling numbers at its historic breeding colony at Mono Lake. But then a few pioneering gulls headed west and established a new colony, in the southern portion of San Francisco Bay. In 1980, there were 24. Today, there are 53,000.

"It's got to plateau at some point," Cheryl Strong, a biologist with the Don Edwards San Francisco Bay National Wildlife Refuge, told the San Jose Mercury News. "Could it double again in the next few years? I don't want to think about that."

The gull boom is wreaking havoc. The birds are colliding with airplanes, aborting takeoffs and landings at Bay Area airports. They're swarming landfills, which use propane cannons and trained falcons to chase them off.

“It’s a constant battle,” said Rick King, general manager of the Newby Island landfill near Milpitas. It spends $300,000 a year to pay for 15 trained falcons, dogs, propane cannons and other tools to keep gulls from eating trash.

Every day in the summer, volunteers stand guard over the nests of endangered shorebirds in the area, blowing air horns at any gulls that approach. The California gull is voracious: it will eat any eggs it can find, including its own.

Getting rid of the gulls is proving tricky. The gull is protected under one of America's oldest environmental laws: the Migratory Bird Treaty Act of 1918, so killing it, or even tampering with its eggs, is illegal. The California gull has a lifespan of 25 years, so the effects of egg-tampering would take years to become visible anyway.

The California gull isn’t the only gull gone wild. Seagulls have taken over southwest England, attacking kids, pets, tourists and mail carriers. Western gulls, which also live in the Bay Area, have started dive-bombing Giants games in the late innings.

One potential gull aid: global warming. A 2006 study of the California gulls that remain at Mono Lake found that the colony’s birth rate varied dramatically from year to year, by more than 45 percent. Two factors seemed to affect the birth rate the most: food and temperature. When the weather was warm, the colony laid more eggs.

In 2007, a group of local park officials, tired of seeing gulls swoop in and eat the eggs of the endangered least tern, banded together and secured a permit to kill up to 45 gulls a year. Out of 53,000, that doesn't seem like many, but for now, it's working.

At Hayward Regional Shoreline Park, wildlife service officials have used shotguns to pick off an average of 20 gulls a year from 2007 to 2011. All those gulls, though, were the worst egg eaters —  or “Charles Manson gulls,” as Dave Riensche, a biologist with the East Bay Regional Park District, described them. "If you remove them," Riensche told the Mercury News, "problem solved."

"It's like in the schoolyard, if you remove the bully, the other kids don't learn that behavior."

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