In the Spotlight: Investigation of Mysterious Brown Pelican Die-offs from WDA’s Reading Assignment Corner

Investigation of Mysterious Brown Pelican Die-offs along the California and Oregon Coasts in the United States

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From their Reading Assignment corner, the Wildlife Disease Association (WDA) has recommended the report, Summary of unusual stranding events affecting Brown Pelican along the US Pacific Coast during two winters, 2008-2009 and 2009-2010. This 30-page report offers detailed information about this investigation. Topics covered include: 1) Live and Dead Bird Observations; 2) Live Recoveries and Findings at Rehabilitation Centers; and 3) Findings from necropsy, histopathology and diagnostic testing.

Excerpt from Executive Summary: Scientists from the California Department of Fish and Game Marine, Office of Spill Prevention and Response - Wildlife Veterinary Care & Research Center (MWVCRC), the National Wildlife Health Center (NWHC), Sea World San Diego (Sea World), California Animal Health and Food Safety Laboratory (CAHFS) and Los Angeles Oiled Bird Care and Education Center (LAOBCEC) rehabilitation center worked collaboratively to investigate the mysterious die-offs of Brown Pelican (Pelecanus occidentalis californicus) along the California and Oregon coasts in the winters of 2008-2009 and 2009-2010 (hereafter “2009 and 2010 events” respectively).

During these events, rehabilitation facilities in CA,OR and WA were overwhelmed by the magnitude of bird strandings. Live-stranded pelicans responded quickly to nutritional supplementation while in care and many were released.

Beach surveys in CA, OR and WA also indicated above normal baseline rates of dead birds deposited on beaches. Postmortem examinations revealed starvation/malnutrition and anemia were major factors contributing to deaths of examined birds.

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A small number of birds died due to trauma or bacterial infections. Some dead stranded birds had atypical prey items in their digestive tracts, such as sea urchins, Docidicus squid, and marine worms (Urechis caupo), indicative of a shortage of more preferred foods such as Northern Anchovy (Engraulis mordax) or Pacific Sardine (Sardinops sagax).

Laboratory analyses indicated no evidence of infectious disease or marine toxins as major underlying causes of these events, although individual animals may have been killed by these causes.

Source Citation: H. Nevins, M. Miller, L. Henkel, D. Jessup, N. Carion, C. Meteyer, K. Schuler, J. St. Leger, L. Woods, J. Skoglund and D. Jaques. 2011. Summary of unusual stranding events affecting Brown Pelican along the US Pacific Coast during two winters, 2008-09 and 2009-10. Unpublished Report, Marine Wildlife Veterinary Care and Research Center, Santa Cruz, CA. 30 pp.

Figure 1: Particularly during the 2009 event, which was associated with very cold weather at the northern edge of the range, some birds had regions of tissue necrosis on non-feathered areas like the pouch and feet. Credit: MWVCRC

Figure 2: Many stranded birds were moderately to severely emaciated, which is characterized by indicated by severe wasting of thepectoralis (breast) muscles and depletion of internal and external fat stores. Credit: MWVCRC

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