From the Disease Investigation Archives
Large mortality of Brandt’s cormorants around San Francisco (CA)
Beginning in mid-April 2009, natural resource agencies, including National Oceanic and Atmospheric Administration (NOAA), California Department of Fish and Game (DFG), and U.S. Fish and Wildlife Service (USFWS) began receiving reports of dead and dying cormorants and other coastal birds in the Bay area. Dead Brandt’s cormorants were found at a nesting colony on Alcatraz Island, and more were recovered on the coast from San Francisco Bay south to Monterey. In addition, dozens of sick cormorants were recovered by several local wildlife rehabilitation centers. Sick birds were found to be extremely emaciated.
Brandt’s cormorants and Western grebes were the primary species affected. Necropsy results from Brant’s Cormorants sent to the USGS National Wildlife Center showed severe emaciation. Tests for domoic acid, a natural marine algae toxin fatal to birds, were negative, as were tests for Newcastle disease, avian influenza and West Nile virus. Researchers speculate that a strong upwelling may have displaced a large amount of water and prey offshore. Since cormorants are near-shore feeders their prey base, including anchovies and juvenile sardines, may have been placed beyond their feeding range. Common murres, another near-shore feeder, were observed to have declined nesting success. Other seabirds that feed further off-shore did not appear to be affected. The die-off ended by late June and a final mortality estimate is being generated, but thousands of birds were thought to be affected. Local USFWS biologists have noted that this pattern is similar to those observed during past El Niño events.
Source: USGS National Wildlife Health Center Quarterly Wildlife Mortality Report, April 2009 to June 2009
View More Disease Cases in California on a Map
The Epizoo Data Viewer summarizes information on mortality events (epizootics) in wildlife gathered by members of the Field Investigations Team at the USGS National Wildlife Health Center in Madison, Wisconsin. Complete data from 1975 to 2003 are included, as well as some data from earlier years.
To explore the Epizoo map begin by:
- Follow the link to the map here
- Click the 'Query' button in the top navigation bar
- In the 'State' drop-down box select California to view case reports
If you know about an interesting past disease investigation, please consider forwarding a brief description with supporting web links to where readers can learn about the case details. Email this information to us at wdin@usgs.gov and we'll share it here on the Digest with your colleagues.
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Last week, we asked readers to share known wildlife photo galleries sites that we missed. A member shared this online gallery, which can be found here.
