A shortage of food is largely to blame for the hundreds of sick or dead brown pelicans that have appeared in recent weeks along California's coastline, wildlife researchers confirmed yesterday.

A series of winter storms since late January has driven anchovies and sardines deeper into the ocean - too deep for the birds to catch, the state Department of Fish and Wildlife said. Some pelicans they studied had little to no body fat and unusual foods in their digestive tracts.

The SeaWorld theme park in San Diego participated in the statewide research project.

Wildlife experts also determined that polluted storm water may be damaging some birds' waterproof feathers, causing them to become soaked and cold. The researchers based their findings on postmortem exams.

They said infectious diseases and waterborne toxins don't seem to be contributing to the problem.

"We are looking primarily at a cyclic event driven largely by weather and oceanographic conditions," said state wildlife veterinarian Melissa Miller in Santa Cruz.