LOS ANGELES -- A mystery is plaguing wildlife experts: Sick, disoriented and bruised California brown pelicans are being found in record numbers from San Francisco to Baja California, Mexico.

The ailing birds, some of them dead, started appearing late last month north of San Pedro in Southern California, then began appearing farther north, said Jay Holcomb, executive director of the Northern California-based International Bird Rescue Research Center.

On Tuesday he said the center's San Pedro center received more than 40 birds in the past seven to 10 days, and the Northern California facility in Fairfield has received about 25 birds.

A man vacationing in Baja California alerted the center about a similar problem there this week after discovering sick pelicans on the beach south of San Felipe.

"There are dead or sick brown's all over the place," Rick Meyer wrote in an e-mail to the research center on Monday. "Normally there are just a couple, but in the last 10 days there is one every 100 feet. And there are the ones that are sick, just standing in the serf (sc) waiting to die. Something's going on."

Holcomb said rescue center researchers have been in contact with Meyer to investigate.

What is unusual is that many of the pelicans have been found far from their homes on roads, farm fields, alleys and backyards.

In the last week, the birds have been reported staggering across Culver Boulevard in Playa del Rey and on a Los Angeles International Airport runway. One bird was reported to have struck a vehicle.

Bird rescuers knew something strange was happening because the increasing numbers of sick pelicans involved adults, 3 years or older, Holcomb said. Typically, this time of year there is a significant die-off of young brown pelicans, but marine biologists say they are seeing a larger-than-normal die-off of adults.

The sick birds are thin, seem confused and disoriented and many have discoloration on their pouches and feet, Holcomb said.

"This type of disorientation in adult pelicans is something we'd see during a domoic acid outbreak, but we have yet to see them exhibiting the other common symptoms," Holcomb said.

Domoic acid, a neurotoxin, is produced by microscopic algae. Birds and sea mammals ingest the acid by eating fish and shellfish that consume the algae.

Birds poisoned by domoic acid generally experience seizures, but the pelicans admitted to the bird rescue centers did not suffer seizures, Holcomb said.

Bird rescuers have sent pelican blood samples and carcasses to state and federal wildlife authorities and laboratories that specialize in detecting potentially fatal algae toxins. Holcomb said results of those laboratory tests are expected in about a week.

Meanwhile, veterinarians and volunteers are nursing the growing numbers of feathered patients with intravenous fluids, medications and a diet of smelt and squid. Holcomb said rescuers have been successful in nursing many of the ailing birds back to health, but the cost is staggering -- about $500 to $1,000 per bird. According to a bird rescue center press release, last year's food bill for pelicans exceeded $60,000 and the center needs donations.

"We will not be able to care for all of these birds unless we receive the financial support to do so," said Holcomb.

The California brown pelican is a subspecies of the common brown pelican. Its habitat stretches from the Sinaloa and Nayarit coast of Mexico to the Channel Islands off the Southern California coast.

Brown pelicans nearly became extinct in the 1960s and 1970s because the pesticide DDT infiltrated their food in nesting grounds such as Southern California's Anacapa Island. The species started to recover in 1972 when DDT was banned in the U.S.