When the oil tanker American Trader ruptured in 1990 and dumped 400,000 gallons of crude into the seas off Huntington Beach, Calif., wildlife experts rescued, cleaned and released 300 oiled seabirds.

A few months later, federal scientists estimated, half of those birds were dead. Many that did survive — brown pelicans, in particular — stopped reproducing.

Today, as international bird rescuers attempt to capture and rehabilitate oiled seabirds after the wreck of a Malaysian-flagged cargo carrier in Alaska, the science of caring for oiled wildlife has improved immensely.

But in recent years, more scientists have questioned whether costly rehabilitation efforts does as much to help animal populations as it does to help humans feel better.

On Dec. 8, the 738-foot freighter Selendang Ayu was ferrying soybeans from Puget Sound to China when it broke apart in a storm off an island in the Aleutian chain. Six crew members died when a Coast Guard helicopter crashed trying to rescue them from the stranded ship.

Since then, more than three-quarters of the vessel's 424,000 gallons of bunker fuel are believed to have poured into the Bering Sea, making it the West Coast's second-largest spill since 1989, behind the American Trader accident. That's the year the Exxon Valdez tanker hit a reef and dumped 11 million gallons of crude into Alaska's Prince William Sound.

As of this weekend, cleanup crews in Alaska have observed at least 726 birds (about 17 different species) and 12 harbor seals oiled by the Selendang Ayu off Unalaska Island. At least two sea otters have died.

Wildlife experts with the International Bird Rescue Research Center have captured 22 live, oiled birds. One is still being cleansed of oil, 12 died or were killed by rescue workers because they were too injured to survive, and nine have been released into the wild.

"Survival depends on a lot of factors," said Jonna Mazet, a zoology professor with the Wildlife Health Center at the University of California, Davis, which coordinates efforts with the rescue center. "Some species are less adaptable and don't do as well. If some get washed too soon, the animals don't make it. If you don't get all the oil off and have to wash them again, that decreases survival."

Oil typically affects birds in two ways: It can poison them if they ingest it, and it can coat their feathers and cause hypothermia. Even rescued birds may suffer dehydration or reduced blood-sugar levels.

A controversial 1996 paper by an Oregon biologist concluded that so few oiled birds survive a spill long enough to be rehabilitated — and so few of those that return to the wild have full lives — that bird rescue should be considered primarily a public-relations effort.

Jim Estes, a biologist with the University of California, Santa Cruz, wrote in 1998 that only 150 of the thousands of sea otters that came in contact with oil during the Exxon Valdez disaster survived, so "it remains unclear whether rehabilitation did any good."

Mazet said techniques have improved significantly since that huge spill so that in many cases, 75 percent or more of rehabilitated birds will survive. She said radio transceivers placed on oiled birds have given new confidence that more birds are surviving than once thought.

But even she recognizes success varies from spill to spill and that the "biological significance" remains unclear.

In 2003, Mazet and others drafted a paper for the journal Marine Ornithology, which concluded that while helpful to individual creatures, it's not clear whether cleaning oiled wildlife does much for entire populations of wildlife. There is also little evidence of how rehabilitation affects reproduction.

But with the cost typically borne by the company responsible for the spill, such efforts will continue, the scientists concluded, because that's what society expects.

Craig Welch: 206-464-2093 or cwelch@seattletimes.com