Biologists Busy at Remote Bird Sanctuary

Russell Bradley will endure noisy, dive-bombing Western gulls, long days and isolation this spring and summer as he counts seabirds in this wildlife sanctuary about 30 miles off San Francisco.

Bradley is among a group of six researchers who live at the Farallon National Wildlife Refuge during bird breeding season, which began in March.

The refuge, located at the edge of the continental shelf, is the largest seabird breeding site south of Alaska and contains 30% of California’s reproducing seabirds.

Almost 250,000 birds of a dozen species are expected to lay eggs and raise their young at the refuge before departing in August. Colonies of three of the species are the largest in the world.

Bradley, a biologist with the Point Reyes Bird Observatory in Stinson Beach, Calif., which has a contract with the U.S. Fish and Wildlife Service to conduct research at the refuge, studies the seabirds to determine their survival rates, numbers of chicks born and raised, and their diets.

Biologists are heartened because populations of most of the species have increased in recent years due to climate changes that have caused a cooling ocean to produce more food. Still, the refuge has a long way to go before the seabirds fully recover from human exploitation of the past. One species -- the common murre -- numbered an estimated 1 million before harvesting of the birds’ eggs during the Gold Rush era virtually wiped them out. Today, the murre population has climbed back to an estimated 100,000.

In addition to seabirds, the refuge is home to six types of marine mammals: the northern fur seal, Guadalupe fur seal, Steller sea lion, California sea lion, harbor seal and northern elephant seal. Sharks, including great whites, abound in the waters around the refuge.

“The island itself is an unbelievably magical place,” said Bradley, 28. “It changes every day.”

Bradley, another biologist and four interns live in an old light-keeper’s house built in the 1870s on the largest of the rugged and remote islands. They work long days -- up to 14 hours sometimes -- collecting information on such species as Western gulls, common murres, Cassin’s auklets, rhinoceros auklets, pelagic cormorants and ashy storm petrels.

The researchers study individual birds that have been banded. Wooden stakes mark the nesting sites of Western gulls that return to the same spot year after year. Although they try to minimize handling of the birds, they measure and weigh them as well as examine the size of the eggs and numbers of chicks that hatch and fledge.

During a recent visit to Southeast Farallon -- part of the 211-acre refuge made up of four groups of small, rocky islands -- thousands of Western gulls dotted the landscape. From time to time, males would hook beaks to fight for territory.

Once the gulls start laying eggs and chicks begin hatching, they turn their aggression on anyone who comes too close.

At that point, Bradley makes sure to always wear his rain jacket.

“The gulls are actively trying to hit you,” he said.

The researchers have been alarmed this spring by the presence of a burrowing owl that is preying on ashy storm petrels. The petrel, the size of a sparrow, can live for more than 35 years.

To catch the predator, which probably came from the mainland in the fall when the island mouse population was high, the researchers strung a net across the opening of a cave, where they had seen petrel feathers. They had documented the owl’s presence on camera.

The researchers took turns one night hiding behind a blind on a hill below the island’s lighthouse to see if they could snare the marauding owl, but they had no luck.

Joelle Buffa, refuge manager, said Fish and Wildlife was considering trying to rid the island of mice through some type of baiting program, pointing out that the rodents were not native to the area.

She said most of the owls that come to the islands for the mice each fall usually leave on their own when the rodent population declines after the rains start.

Bradley, who helped write a report on the results of last year’s research, said the overall picture for the island’s birds is positive. “Reproductively, we’re seeing, for some species, the highest populations in 20 years,” he said.

That is in sharp contrast to the 1990s, when seabird populations declined markedly, he said. There was a smaller dip in reproduction rates last year, however, due to a “mild El Nino event,” he added.

Bradley said biologists believe that when the ocean is cooler, it produces more plant and sea life. That, in turn, provides more food for the seabirds, allowing their populations to flourish.

William Sydeman, director of marine ecology at the Point Reyes Bird Observatory, said his group has been studying Farallon bird life since 1971, the longest seabird research project in the North Pacific. “The focus of our work is looking at the effect of climate change,” he said. “Our primary interest is in looking at how things change over the decade.”

The cooling of the ocean began in 1999, Sydeman said. He said scientists do not know how long it might last, but it appears to be part of a natural climatic cycle.

For now, though, he and the other biologists are delighted that the seabird populations are growing.

“The news is good,” Sydeman said, “but we’re still a long way from where we could be.”