Determined to eradicate mice and protect a rare seabird on the South Farallon Islands, a federal wildlife agency is planning to drop poison pellets from a helicopter all over the rocky islands 30 miles west of San Francisco.
Twenty-one scientists and environmentalists, including members of the Audubon Society and the California Academy of Sciences, are backing the U.S. Fish & Wildlife Service's proposal to wipe out the house mouse, an invasive species that periodically swarms the islands at a "plague-like density" of nearly 500 mice per acre.
The mice eat crickets and salamanders, but their primary harm is attracting to the islands a small number of burrowing owls that prey on mice until the rodent population plummets in midwinter. That prompts the owls to switch to a diet of ashy storm-petrels, a small sooty-brown seabird that depends on Farallones breeding sites for survival.
Expressing "strong support" for the eradication of the mice, the scientists acknowledged in a letter to the Fish & Wildlife agency that widespread poisoning may be necessary.
In an environmental report of more than 700 pages, the agency said that broad application of poisonous bait is "the only available and proven method" of exterminating the mice.
Poisons have been used worldwide to remove mice and rats from islands, including a black-rat eradication on Anacapa Island off Southern California in 2001.
But questions about the wisdom of dispersing lethal toxins in the midst of a federally protected marine preserve are coming from environmentalists, including a Marin County group called WildCare and members of the Gulf of the Farallones National Marine Sanctuary Advisory Council.
"It's like using a Hellfire missile to get rid of a gnat," said Richard Charter of Bodega Bay, the council's vice chairman, at a meeting last week.
Charter, best known for fighting offshore oil drilling on the North Coast, said the poison pellets would wind up in the water, potentially reaching black abalone, an endangered species, and Dungeness crabs at the start of the commercial crab season.
"What they're going to do at the Farallones is not just poison the mouse but the whole ecosystem," he said.