PRBO Conservation Science
Quarterly Journal of PRBO Conservation Science, Number 151, Winter 2008: The Science of Oil Spill Assessment

Perspectives on the 2007 Cosco Busan spill in San Francisco Bay


The Science of Oil Spill Assessment

Diana Humple

Securing Oil Spill Data
CEO's Column
Cosco Busan Damage Assessment
PRBO's Oil Spill Expertise
Assessing Population Impacts
Protecting the Farallon Islands
Western Grebe Genetic Study
Schoolchildren Take Action
Focus: A Birder's Library
Views of a Planned Giving Expert
PRBO's New Chief Science Officer
The Grand List
Bird-A-Thon Update

Surf Scoter (here, two males in flight) is a diving, salt-water duck—and the species most commonly recovered after the 2007 Cosco Busan oil spill in San Francisco Bay. Photo © Peter Latourrette,

Surf Scoter, Western Grebe, Greater Scaup, Eared Grebe, Common Murre, Brandt's Cormorant. These are among the diving waterbirds that abound in San Francisco Bay and the nearshore ocean during fall and winter. They were the species most commonly collected after the cargo vessel Cosco Busan struck the Bay Bridge on November 7th, spilling 58,000 gallons of crude fuel oil. Throughout the response that followed, PRBO's focus has been the rigorous collection of scientific information—crucial for understanding an oil spill's full impacts on birds and supporting their recovery.

Securing Data and Evidence

During the Cosco Busan oil spill, a team of PRBO biologists worked intensively for two months at the San Francisco Bay Oiled Wildlife Care and Education Center in Cordelia, California (just northeast of the bay). As part of the state's Oiled Wildlife Care Network (OWCN), PRBO was involved in "wildlife processing"—documenting all birds brought to the center and helping collect data and evidence from each one. Such information is crucial, both for monitoring impacts during the response and for assessing the spill's large-scale effects on populations. Data is potential evidence in legal determinations of impacts on wildlife (see the articles that follow by Nadav Nur and Gary Page).
Western Grebe is abundant at the coast in winter and vulnerable to the impacts of floating oil slicks. Photo © Tom Grey

Gathering information is a high priority of OWCN—and is very demanding. Early in the Cosco Busan response, our days were a blur of non-stop, high-pressure activity for up to 16 hours (many members of the PRBO team suspended normal routines to relocate near the wildlife center). We were often inundated with hundreds of new birds arriving in large batches, both live and dead. Though collecting data and evidence from carcasses was a critical part of our role, it could wait, as live birds had to take precedence. So, when large plastic bags full of dead birds came in, we would log them in, assign them numbers, and set them in the increasingly crowded freezer. Live birds—arriving in need of medical attention, at risk of hypothermia, and dehydrated—had to be assessed immediately so that skilled personnel could begin their rehabilitation.

Cautiously opening one live-animal carrier box at a time, we would peer inside to note the species and assess the bird's condition. Some had plumage completely obscured by oil, requiring close examination just to identify. As with the dead birds, we assigned each a log number: this would track the bird throughout its stay, along with all the associated data and evidence. We worked closely with the rehabilitation staff when they conducted medical examinations: we helped collect oiling data, an oiled feather sample for potential chemical analysis, and a photograph of each bird for evidence.
PRBO's Renée Cormier and a batch of oiled birds in live-animal carrier boxes. Photo by Diana Humple/PRBO

Following the OWCN protocols (which PRBO helped develop), we sometimes needed hours to get through a batch of birds. Then, just when we thought we might get some respite from the emergency room intensity, someone would announce another delivery. We would rush out to help bring box after box of birds inside, where warm "tropical" conditions made them safer from hypothermia—and start the exacting process again.

Once the activity calmed down a bit, more team members could focus on collecting data from the carcasses. Pairs of us worked together, one person examining the bird and the other, wearing gloves not coated in oil, recording information. Along with species identification (challenging if the dead bird was very oiled or was missing body parts, having been scavenged), the examiner's job was to assess the carcass—whether oiled, what percentage, where on the body, and how deeply oil penetrated the feathers. Along with a feather sample and photograph for each bird, the carcass itself was evidence, so we wrapped and labeled and stored it in a numbered box.

With a total of 1,864 dead birds and 1,084 live ones collected, the Cosco Busan event was significant in California's unfortunately rich history of oil spills. It remains to be determined how much of the total impact these numbers represent (see note by Steve Hampton), but the state's oil spill response protocols recognize the importance of data collection—recognition that is lacking in many other regions. PRBO, with our scientific credentials and bird expertise, fits into California's official response structure, and we remain on call to respond to future spills in the region.

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