Warmer waters disrupt Pacific food chain

FARALLON NATIONAL WILDLIFE REFUGE, Calif. - On these craggy, remote islands west of San Francisco, the largest seabird colony in the contiguous United States throbs with life. Seagulls swarm so thick that visitors must yell to be heard above their cries. Pelicans glide.

But the steep decline of one bird species for the second straight year has rekindled scientists' fears that global warming could be undermining the coastal food supply, threatening not just the Farallones but entire marine ecosystems.

Tiny Cassin's auklets live much of their lives on the open ocean. But in spring, these gray-and-white relatives of the puffin venture to isolated Pacific outposts like the Farallones to dig deep burrows and lay their eggs.

Adult auklets usually feed their chicks with krill, the minuscule shrimp-like crustaceans that anchor the ocean's complex food web.

But not this year. Almost none of the 20,000 pairs of Cassin's auklets nesting in the Farallones will raise a chick that lives more than a few days, a repeat of last year's "unprecedented" breeding failure, according to Russ Bradley, a seabird biologist with the Point Reyes Bird Observatory who monitors the birds on the islands.

Scientists blame changes in West Coast climate patterns for a delay in the seasonal upwelling of cold, nutrient-rich waters from the ocean's depths for the second year in a row. Weak winds and faltering currents have left the Gulf of the Farallones without krill, on which Cassin's auklets and a variety of other seabirds, fish and mammals depend for food.