Trends in Caspian Tern Nesting and Diet in San Francisco Bay: Conservation Implications for Terns and Salmonids

• Main Authors: Collis, Ken, Roby, Daniel D., Larson, Keith W., Adrean, Lindsay J., Nelson, S. Kim, Evans, Allen F., Hostetter, Nathan, Battaglia, Dan, Lyons, Donald E., Marcella, Tim, Patterson, Allison
• Other Authors: Fisheries and Wildlife
• Format: Article in Journal/Newspaper
• Language: English; unknown
• Published: The Waterbird Society
• Subjects: South Bay; North Bay; Knight Island; Brooks Island
• Online Access: https://ir.library.oregonstate.edu/concern/articles/1n79h470d

Colony size, nesting ecology and diet of Caspian Terns (Hydroprogne caspia) were investigated in the San Francisco Bay area (SFBA) during 2003-2009 to assess the potential for conservation of the tern breeding population and possible negative effects of predation on survival of juvenile salmonids (Oncorhynchus spp.). Numbers of breeding Caspian Terns declined 36% from 2003 to 2009, mostly due to abandonment of the Knight Island colony and decline of the Brooks Island colony, the two largest colonies in the SFBA. Concurrently, nesting success declined 69% associated with colony site characteristics such as (a) quality and quantity of nesting substrate, (b) vulnerability to nest predators, (c) displacement by other colonial waterbirds and (d) human disturbance. Marine fishes were the predominant prey in tern diets from the SFBA; however, diet composition varied among colonies. Juvenile salmonids comprised 22.9% of the diet of terns nesting in the North Bay, 5.3% of diet of terns nesting in the Central Bay, and 0.1% in the South Bay. Construction or restoration of nesting islands in the South Bay may help maintain and restore breeding Caspian Terns without enhancing mortality of salmonid stocks of conservation concern. This is the publisher’s final pdf. The published article is copyrighted by The Waterbird Society and can be found at: http://www.waterbirds.org/journal Keywords: diet composition, productivity, colony size, Hydroprogne caspia, Caspian Tern, colony restoration, Oncorhynchus, salmonids, limiting factors, San Francisco Bay