The first batch of seabirds treated after being coated with a mysterious deadly goo in the Bay Area are scheduled to be released today and the gunk that took a toll on hundreds of them has dissipated. But rescue personnel are still trying to identify what the stuff is and who is responsible for it.

More than 100 birds died after being brought to the International Bird Rescue facility in Fairfield for treatment. They were covered in a sticky goo with rubber cement qualities, which mats their feathers, causing them to lose insulation and suffer from hypothermia.   Another 220 birds are recovering.

The birds first started showing up on January 16 in the East Bay, near Oakland, Hayward and Alameda, along shorelines and trails. They are mostly Surf Scoters, Horned Grebes, Scaups and Common Goldeneyes.

A week later, rescue workers were still pulling birds from San Leandra Marina. They quickly eliminated oil as a culprit and California’s Department of Fish and Wildlife (DFW) said polyisobutylene, a synthetic rubber and fuel additive, was ruled out too.

A department spokesman told the San Francisco Chronicle that they had not eliminated the cause being some form of natural occurrence, like an algae bloom that killed hundreds of birds on the Pacific coast in 2007. But Barbara Callahan, the rescue facility’s interim executive director, told the Associated Press that it’s probably a man-made product.

“The goo appears to be light gray in color and to me looks like rubber cement that's been played with all day and is sort of dirty,” she said. “It has very little smell.” The goo was found to be much harder to remove than oil.

Since the authorities have not yet identified a responsible party, the nonprofit rescue center has absorbed the $9,500-a-day cost of caring for the birds. The center has a full-time staff and about 40 volunteers.

–Ken Broder

To Learn More:

Mystery Deepens: Experts Probing Bay Goo Rule Out Polyisobutylene (by Steve Rubenstein and Peter Fimrite, San Francisco Chronicle)

Toll Increases to 200 Dead Birds from Mystery Goo in San Francisco Bay (by Denis Cuff, Bay Area News Group)

San Francisco Bay: Number of Dead Birds Climbs to 100; 300 Rescued (by Denis Cuff, Bay Area Newsgroup)

San Francisco Bay Area Bird Deaths Blamed on Mysterious Goo (by Kristin J. Bender, Associated Press)

Mystery Goo (not Oil) Kills Bay Area Birds, Baffles State Officials (by Joseph Serna, Los Angeles Times)