Spatial and temporal trends of contaminants in eggs of wading birds from San Francisco Bay, California

Environmental Toxicology and Chemistry
By: , and 



Between 1989 and 1991, reproduction by black-crowned night-herons (Nycticorax nycticorax) and snowy egrets (Egretta thula) was studied at sites in San Francisco Bay. Eggs were collected from these and other bay sites and from South Wilbur Flood Area, a reference site in California's San Joaquin Valley. Eggs were analyzed for inorganic trace elements, organochlorine pesticides, and polychlorinated biphenyls (PCBs). Results were compared among sites and years and with results of previous studies. There was some evidence of impaired reproduction, but concentrations of contaminants were generally lower than threshold levels for such effects. Egg hatchability was generally good, with predation being the factor that most limited reproductive success. Mean PCB concentrations were generally higher in eggs from the south end of San Francisco Bay than from the north, but the only temporal change, an increase, was observed at Alcatraz Island. There were spatial differences for p,p'-DDE in night-heron eggs in 1990, but the highest mean concentration of DDE was in night-heron eggs from South Wilbur in 1991. Temporal declines in maximum concentrations of DDE in eggs were observed in the bay, but means did not change significantly over time, At Bair Island in the southern end of the bay, mean concentrations of mercury decreased while selenium increased in night-heron eggs over time, but there were no clear bay-wide spatial or temporal trends for either element.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Spatial and temporal trends of contaminants in eggs of wading birds from San Francisco Bay, California
Series title Environmental Toxicology and Chemistry
Volume 14
Issue 8
Year Published 1995
Language English
Contributing office(s) California Water Science Center, Patuxent Wildlife Research Center
Description 1319-1331
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Environmental Toxicology and Chemistry
First page 1319
Last page 1331
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