San Francisco Bay Bird Observatory - Project Summary

Title of the project: Heavy metal accumulation, foraging patterns and breeding success in an indicator species on San Francisco Bay: Terns & Cormorants

Related education program title: "Birds & Bioaccumulation in the Bay"

The San Francisco Bay Bird Observatory is a not-for-profit research organization dedicated to the conservation of birds and their habitats through research, monitoring and educational activities. Scientific information is provided to governmental agencies, industry, and the public to support informed resource management decisions for the San Francisco Bay area.

The San Francisco Bay has seen massive changes in the last 150 years. Over 90% of the Bay's wetlands have been lost to fill or degradation. Wildlife species and their habitat are threatened by development, pollution, human disturbance, and introduced species. Despite the loss of natural habitat, San Francisco Bay's remaining ponds, marshes, sloughs and uplands are critically important to our resident and migratory bird populations, and home to several endangered species.

Major changes are being proposed for San Francisco Bay. The Bay already is known to carry a variety of contaminants, including heavy metals. The proposed airport runway expansion and its mitigation scenarios may greatly alter the hydrology of the San Francisco Bay. This project, along with proposed port and ferry service expansions, will require extensive dredging, which stirs up the bay's mud and releases even more contaminants into the water column. We need to continue our 18 years of monitoring the waterbirds that nest and forage in south San Francisco Bay and to measure the heavy metals already present in these fish-eating birds.

We received funding to conduct research to obtain baseline data on heavy metal contamination (selenium, mercury, nickel, cadmium) in terns and cormorants and relate it to these birds' fish prey base, foraging patterns, breeding success and population trajectory in San Francisco Bay. Given its relatively high position in the trophic food chain, the Forster's Tern, for example, has been identified as a community indicator species in San Francisco Bay (Goals Project 1999). This project will:

• Determine heavy metal contamination in the terns and cormorants. Because this bird feeds on a wide variety of fish in the bay, the results will have direct relevance to the communities of the bay and to the people relying on Bay-caught seafood.
• Determine population trajectory of terns and cormorants breeding in San Francisco Bay.
• Determine the foraging patterns of the terns and cormorants on San Francisco Bay to ascertain the most likely areas where terns are acquiring heavy metals from their prey.
• Provide hands-on experience in environmental monitoring and research to 40-60 volunteers.
• Provide results to the public through a final report and scientific publication.

This will be the first comprehensive data of its kind on heavy metal contamination in higher trophic level birds, such as the Forster's Tern, in the SF Bay environment. This unique research will involve the public in an entirely new approach to measuring environmental health in the San Francisco estuary.

We are currently acquiring the last of lab work results and will be analyzing the rest of this year's data. Further, we are gearing up for next season to carry out the third year of this project. Look for more soon…
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Basic Project Info:

Study Questions:

• Are eggs of terns and cormorants contaminated?
• Do high levels of contaminants in sample eggs correlate with adverse effects on nest success?

Process:

Contaminant levels in bird eggs represent levels in the prey items of the foraging female, generally from the breeding grounds because terns and cormorants are high trophic level feeders. Eggs were tested to determine environmental contaminant levels.

• We collected eggs from tern and cormorant colonies during the nesting seasons, 2000-2002
• Tested eggs for levels of PCBs and mercury
• Most of the data presented here is 2000 and some 2001
• The rest is still in the lab...

We also returned to tern colonies at approximately one-week intervals during the 2002 nesting season to determine hatching success at each colony where eggs were collected to see if contamination levels in eggs correlated with nest success within a colony.

Graph Info:

Preliminary Results:

X axis: three regions of the Bay
Y Axis: average percent success rate of chicks to about one week, for all eggs in colony with known fate (fledge at about 30 days for Caspian tern's)

One site each for Forster's terns and Caspian terns in North Bay - huge discrepancy between the two species: hatch rate for Caspian terns was at its highest in the Bay overall at about 47%, while Forster's terns were at their lowest at only 8% located only about 1/2 km apart

Central Bay: again one site each, Forster's tern's much lower again

South Bay: one site for Caspian tern's with the lowest hatch rate success of all three regions (about 23%) two sites here for Forster's tern's- one of these sites had a 48% success rate, the other site was similar to the north and central bay sites single colony of Forster's tern's in entire Bay doing well is this one in the south (note: this site also had a higher average clutch size than the other Forster's tern sites, more nests with3-4 eggs as opposed to 2-3 eggs)

A second year of hatch success data is to be collected during the 2003 nesting season. Note that this is chick success data, up to one week of age, for 2002 only. No fledgling data. Will continue to collect data in 2003 season.
(Comparison: Columbia River hatch success: ranges from 5-40% for Caspian tern's; 1997/1998)
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