Killing the Rats to Save the Birds

In a boat anchored near Anacapa Island off the Ventura County coast, biologist Paige Martin holds a tiny baby bird.

It’s easy to see what makes this species rare: It is only a vulnerable bit of fuzz plucked from its chirping mother’s side in the ocean.

And on another boat, biologist Gus van Vliet holds something even more telling: a speckled Xantus’ murrelet egg, serrated, the edges nibbled and cracked by a black rat’s pin-sharp teeth.

On Anacapa, in the grotto where van Vliet found this egg, the black rats are merciless.

“It’s an extinction game,” he said.

In the fall, state Department of Fish and Game biologists plan to kill Anacapa’s entire rat population, the first effort to get rid of up to 3,000 rats living on the three islets that make up the island.

It is a plan that scientists believe could save the Xantus’ murrelet. And they are using the opportunity to study a species they know very little about: this palm-sized, black-and-white bird.

The birds are the innocents, not built for survival on an island where black rats were introduced as predators. And they are like millions of island-nesting birds across the world threatened by these unwanted neighbors.

The black rat eats whatever it can, scurrying up cliffs, stealing eggs from under flustered parents, and sometimes rolling them down bluffs to save for later.

Though efforts to eradicate the rats have worked on some islands around the world, others have failed because rats breed so quickly that a single mating pair could result in a population of 5,000 in a year.

In the 1980s, the Channel Islands National Park Service set rat traps by hand, but found the task impossible because of the island’s rugged slopes.

This time, the Park Service will use helicopters to drop tons of poison pellets on the island. The east end will be targeted first and the rest by next year.

Although a trial run last year succeeded, parks officials said, there is one drawback: The pellets kill some native deer mice. Biologists plan to set aside a group of the mice that will breed later.

The project will cost about $700,000. That money comes from part of a $9.1-million settlement with BP America, stemming from the 1990 American Trader oil spill off Huntington Beach.

The plaintiffs included a number of regulatory agencies such as the state Fish and Game, the California Regional Water Quality Control Board and the state Coastal Conservancy.

The murrelet and other seabirds were among the probable victims of the Orange County spill, so it made sense to pay for their restoration in other Southern California locations where they breed, said Carol Gorbics, a biologist with the U.S. Fish and Wildlife Service.

It is part of an ongoing program to return the park to its native state by removing, alive or dead, such nonnative interlopers as sheep, burros, rabbits, pigs and golden eagles.

The murrelets number about 10,000 in the world and about 3,000 in California, with only about 100 to 200 pairs on Anacapa Island. They are particularly vulnerable because they nest in the same cliffs and grottoes that house the black rat population.

“They’re living right there with the rats,” Gorbics said. “They don’t have a chance.”

Once baby birds are two days old, their parents nudge them down the cliffs, where they join their parents in the water. Biologists still know very little about their habits, but they do know that they spend most of their lives at sea.

Adult birds fly only by night, when they aren’t bound to be food for sea gulls. As for what the murrelets eat, the experts don’t know for sure but suspect it might be anchovy larvae.

One key goal now is to get a baseline of the current bird population. Then, after five years of returning and counting, they will know if the rat kill worked.

The scientists already are petitioning for endangered or threatened species status for the small birds. But, if the rat kill works, that may not be necessary.

“There’s so much bang for the buck,” said van Vliet. “In five years, I think, their populations could double.”