Hitchhiking seagull takes 150-mile truck ride along California freeways

They say the early bird catches the worm.

But in the case of one adventuresome seagull, it can also catch a ride. On a truck. Zooming 75 miles down Northern California freeways. On two different occasions.

A San Jose State University researcher who uses GPS tags to track Western gulls living on the Farallon Islands off San Francisco made an unusual discovery recently: Data from a tag he attached to the tail feathers of one gull showed it had mysteriously “flown” from San Francisco, directly up Highway 101, across the Bay Bridge, down Interstate 880 near Oakland, and along Interstate 580 through the Altamont Pass to a composting center in the Central Valley, near Modesto.

And rather than the 20 mph that gulls normally fly, the bird made the whole 75-mile journey considerably faster.

“The bird was traveling at 60 mph,” said Scott Shaffer, an associate professor of biology. “That’s clearly not flying speed.”

His conclusion: The intrepid gull rode the whole way on a garbage truck.

The bird’s journey began at a transfer station in South San Francisco near Candlestick Point that is run by Recology, the company that handles San Francisco’s garbage collection. There, garbage trucks bring trash and composting materials like food scraps and grass clippings from San Francisco neighborhoods to be loaded into larger, 18-wheel trucks. Those trucks, which don’t compact the garbage like the smaller trucks do, then haul the composting materials to a Recology composing center Vernalis, 15 miles east of Modesto, and trash to a landfill near Vacaville.

Shaffer thought that the globe-trotting gull might have been scavenging food at the station and gotten trapped in a truck.

But then the baffling part: As he kept reviewing the GPS data from the tag he recovered from the bird at its nest, he saw that two days later, the same thing happened again. Another 75-mile truck ride by the same bird.

This time the bird, a female who goes by the name “#14″ because that’s the number of the tiny metal ID band scientists put on her leg, boarded a truck at the same Recology transfer station in San Francisco, and rode it south on Highway 101, across the San Mateo Bridge, and out Interstate 580 to the same composting facility.

Was that a freak occurrence twice in two days? Wrong place, wrong time for the gull? Or did the bird learn the first time that it got rewarded for riding the truck with lots of food at the composting facility, and then deliberately climbed on a truck the second time?

If so, it might be the only time a San Francisco resident ever drove to Modesto for dinner.

“Gulls are smart,” said Cheryl Strong, a wildlife biologist with the Don Edwards National Wildlife Refuge in Fremont.  “This one might have accidentally learned that. In the bigger picture what else can they learn? Maybe this bird will take its kids there and say if you get in this truck, you can get better food somewhere else.”

Both instances occurred in late May. The gull stayed overnight at the Recology Blossom Valley composting facility near Vernalis both times, then flew back to the Recology transfer station in San Francisco, waited a few hours, and returned to her nest on the Farallon Islands about 27 miles west of San Francisco.

Robert Reed, a spokesman for Recology, said that officials at the transfer station have never heard of gulls riding garbage trucks before. He said that the trucks are 14-feet high. When composting material is loaded into them, the drivers get out and use a metal pole to pull a mesh-like tarp over the contents, to keep it from falling off the truck when it is motion.

“We suspect the gull flew into the truck to try to snatch a food scrap, and got trapped in the brief period from when the truck was loaded and the driver pulled the tarp over the truck,” he said. “The driver can’t see into the top of the truck and would have been unaware this had happened.”

But how did the same bird do it twice in two days?

Reed said he has no idea. The transfer station, like other garbage collection facilities in the Bay Area, deals with the nuisance of gulls all the time. It even pays a falconer to use birds of prey like hawks and falcons to chase them away.

But as every San Francisco Giants fan knows — having watched gulls swarm over the field at AT&T Park in the final innings of every home game, regardless of whether the game starts in the day or night — gulls are determined and clever.

Shaffer said he tracked one riding on a large ship for miles under the Golden Gate Bridge. Others regularly “commute” every day from Año Nuevo Island in San Mateo County to the city landfill in Santa Cruz. When he has checked their stomach contents, he has found everything.

“A whole hot dog. Barbecue ribs. Chicken. Squid. It’s really variable,” Shaffer said.

Shaffer said he wants to go to the Recology facility and learn more, including whether there are more hitchhiking birds. It’s all part of learning about how the species adapts, and how gulls’ diets have changed as human population has grown.

“Is this a regular occurrence?” he said. “Maybe it’s more common than we realize.”

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