California Gull Research
California Gulls are the most common gull species in the South San Francisco Bay, especially during the breeding season. Since the early 1980s, our biologists and citizen scientists have monitored California Gull populations in the South Bay, and documented a dramatic increase from less than 50 breeding birds to over 50,000 breeding gulls in 2014. California Gulls may have negative effects on other ground-nesting birds and have been found to be significant predators of American Avocet, Black-necked Stilt, and Western Snowy Plover eggs and chicks.
However, recently, gull numbers have been decreasing in the Bay Area. The former South San Francisco Bay salt pond where 23,000 California Gulls nested until 2010 (Pond A6) was restored to tidal action in December 2010. Many of the gulls, presumably displaced by the restoration, moved to new nesting colonies in Alviso. This survey helps us determine if and where displaced California Gulls establish new colonies. We've also banded over 10,400 California Gulls since 1983 (over 1,000 of these at Pond A6 before the levee was breached) in order to track their movements.