Research Technical Report

BeachCOMBERS: Monitoring Changes in Oiling Rates of Beached Marine Birds in the Monterey Bay National Marine Sanctuary

Nevins, H., K. Newton, J.T. Harvey, S.T. Benson, and A. DeVogelaere (March 2003)

Poster presentation at the Sanctuary Currents Symposium, Seaside, CA

ABSTRACT

In 1997, we initiated the Coastal Ocean Mammal and Bird Education and Research Survey (Beach COMBERS) to monitor deposition rates of marine birds within the Monterey Bay National Marine Sanctuary (MBNMS). Chronic oil pollution, originating from leaking shipwrecks, urban runoff, and additional nonpoint sources, continues to affect seabirds in the MBNMS. The average oiling rate (percent oiled carcasses km -1 month-1) during 1997-2002 (2 %) was less than recorded during 1971—1985 (8 %) by Pt. Reyes Bird Observatory. During 1997-2002, the greatest percentage of oiled birds occurred during November to May (2.2—9.8 %), and the least oiling rate occurred during June to October (0.2—2.1 %). Beach COMBERS recorded the greatest numbers of oiled birds during the 1997-98 Pt. Reyes Tarball Incidents. Species composition of oiled birds was similar among surveys, affecting mainly alcids (17- 20 %), and wintering loons (9 %), and grebes (7 %). Our comparison with past data indicates that oil pollution prevention measures implemented during the past 20 years have likely reduced oiling rates. However, the persistent occurrence of oiling (71 % of surveys have at least 1 oiled bird) indicates that chronic oiling is still a major problem for both resident and migratory seabirds in the MBNMS. Continued efforts to monitor oiling rates and document species-specific deposition patterns will aid sanctuary managers and help to identify those seabirds most vulnerable to oil pollution.