Mystery Goo Injuring Hundreds of Seabirds in San Francisco Bay

An as-yet unidentified substance is fouling the feathers of hundreds of birds on the east shores of San Francisco Bay, and at least 25 of the affected birds have died, reports a California bird rescue organization.

As of Sunday night the group International Bird Rescue has reported 179 seabirds contaminated with the unidentified sticky substance, which gums of feathers and can thus interfere with the birds' ability to float and to regulate their body temperature. Twenty of the dead birds died after being transported to the group's rehabilitation facility in Fairfield, which has hosted numerous bird cleanups after oil spills in the Bay.

The unidentified substance seems not to be petroleum based. Initial suspicions are that it may be polyisobutylene, a synthetic rubber that caused the deaths of thousands of seabirds in the United Kingdom in 2013, though laboratory tests of the substance are not yet available.

Polyisobutylene is used in a wide range of industrial applications from inflatable tires to chewing gum, but the chemical's use most likely to be relevant to seabird deaths -- if the rubber does turn out to be the culprit in the birds' injuries -- is as a lubricant in ship engines.

Contaminated birds have been found up and down the eastern shoreline of San Francisco Bay from Alameda, near the Oakland Airport, to shoreline parks in San Leandro and Hayward. International Bird Rescue's interim executive director Barbara Callahan says that the unknown substance posed a challenge for the group's trained rehab workers.

"The good news is that we have modified our wash protocol and it appears to be working on healthier birds," Callahan said. "However, some of the birds that have recently arrived are in much poorer condition, likely because they've had this substance on their feathers for several days now."

As many as 60 soiled birds were expected to be brought into the rehab center on Monday. Among the injured birds are surf scoters, buffleheads, and horned grebes. So far many fewer birds have been reported injured in this mystery spill than were harmed during the 2007 Cosco Busan spill in the Bay, which killed thousands of seabirds, but the unknown nature and source of this sticky goo has wildlife workers worried.

As the substance befouling the birds' feathers is as yet unidentified, it's hard to determine who might be responsible for its presence in the Bay. If a source is found, that source can be held liable for expenses involved in cleaning the seabirds. In the meantime, International Bird Rescue has set up a crowdfunding site to pay the initial costs of the cleanup.