The San Francisco Bay Bird Observatory (SFBBO) requested funding to build on over 20 years of monitoring the reproductive success of Forster’s and Caspian terns by this organization. During the past two years, they have expanded our breeding season fieldwork to include an analysis of contamination levels in tern eggs and an examination of possible sources of exposure. The staff (and Volunteers???) collected eggs and surveyed tern colonies for reproductive success to determine the effects of contamination on reproductive patterns in these birds.

With their research partner, the U.S. Fish and Wildlife Service, SFBBO planned colony visits in Santa Clara, Alameda and Solano Counties and collection schedules to all the major tern colonies in San Francisco Bay.

Results of their two main objectives:
1) determining levels of contaminants, and
2) establishing reproductive success rates, are summarized below.

The high concentrations of mercury and PCB's combined with patterns in tern reproductive success indicate that there may be adverse effects occurring in these species that may have population level consequences. Initial patterns of mortality indicate that a sensitive stage for effects of contaminants and consequences on population parameters in breeding terns may be the nestling stage. Information on nestling and juvenile survival rates is lacking for the San Francisco Bay. These are important future parameters to estimate in assessing the health of a breeding population and to successfully manage these species.

San Francisco Bay Bird Observatory "Tern Contaminants" Study
Contamination and Hatching Success in Forster's and Caspian Terns in the Bay.