Dying Cormorants: Unique Partnership Monitoring Die-Off

Brandt's Cormorant

By Mary Jane Schramm

In mid-April, Farallones Beach Watch volunteers, along with numerous other wildlife agencies and organizations, began to note an increase in dead Brandt’s Cormorants along beaches from Marin to Monterey counties. As of May 25, 2009, Beach Watch surveyors have documented 380 dead Brandt’s Cormorants during the months of April and May. Increased numbers of dead grebes (also diving seabirds) have also been found on beaches.

Gulf of the Farallones National Marine Sanctuary is working to determine the extent of the event and find the cause with a large number of seabird management and research groups: FMSA, U.S. Fish and Wildlife Service, National Wildlife Refuge System for California and Oregon, National Park Service, California Department of Fish and Game/Office of Spill Prevention and Response, PRBO Conservation Science, Audubon Society, Oiled Wildlife Care Network, International Bird Rescue Research Center, University of Washington. NOAA's Cordell Bank, Monterey Bay, Olympic Coast and Channel Islands national marine sanctuaries, NOAA Fisheries, and many local rescue and rehabilitation centers throughout the Monterey and San Francisco Bay areas are also involved.

Farallones science staff are tracking oceanic and atmospheric conditions back to mid-April, the time when the spike in dead seabirds began, looking for unusual wind and wave patterns, and for possible connections to the feeding habits of the cormorants. Until a complete analysis of these conditions and fish distribution is conducted, scientists can only speculate on the cause of the die-off. According to NOAA records, April 2009 had the highest upwelling index – the most intense sustained upwelling forces in a decade.

However, cormorants and grebes pursue small fish such as anchovies, flatfish and sardines in nearshore coastal waters. Unusually cold water conditions, often referred to as La Nina, may force fish to other areas outside our region. Also, April’s unusually strong and sustained winds may be physically pushing the fish out of the region. If the birds don’t move offshore along with the fish, or switch to other nearshore prey, starvation could result. Animals that are slow to adapt to changes in the location and type of prey will be more susceptible to starvation than species that can switch quickly among various kinds of food.

Sanctuary Research Coordinator Jan Roletto states, “If ocean and atmospheric conditions return to moderate levels, the cormorants will be able to rebound next breeding season without much decline in their population. Ocean productivity depends on a certain combination of windy days, then periods of wind relaxation, followed by more windy days.” She continues, "This is a significant event. Beach Watch’s preliminary data show mortality at least 4.5 times as high as anything we've seen in the past 15 years, including the normally occurrence of peak mortality during post-breeding months."

In the meantime, agencies request that the public leave dead birds alone, to ensure they are recorded during beach surveys conducted by the Gulf of the Farallones and Monterey Bay national marine sanctuaries who will document numbers and locations.

Live, sick birds can be reported to local animal control or wildlife rehabilitation groups. If wildlife appears oiled or otherwise contaminated report it to the Oiled Wildlife Care Network at 1-877-UCD-OWCN (1-877-823-6926). If there is a large concentration of dead birds in one area, call (831) 469-1745 to the Marine Wildlife Veterinary Care and Research Center.