The relationship between plankton-feeding Bonaparte's and Mew Gulls and tidal upwelling at Active Pass, British Columbia

• Published in: Journal of Plankton Research
• Main Authors: Vermeer, Kees, Szabo, Ildy, Greisman, Paul
• Format: Text
• Language: English
• Published: Oxford University Press 1987
• Subjects: Articles; Thysanoessa raschii
• Online Access: http://plankt.oxfordjournals.org/cgi/content/short/9/3/483; https://doi.org/10.1093/plankt/9.3.483

The food habits of Bonaparte's ( Larus Philadelphia ) and Mew Gulls ( L. canus ) were studied at Active Pass, British Columbia, in relation to upwelling of zooplankton. Bonaparte's Gulls fed mostly on planktonic crustaceans during September-November and again during April-May, while Mew Gulls foraged there chiefly in February and March. Both species ate predominantly the euphausiid, Thysanoessa raschii , in spring, while Bonaparte's Gulls fed mainly on the amphipods, Parathemisto pacifica and Calliopius laeviusculus , in fall. Year-round sampling of zooplankton and collection of temperature and salinity data showed gull numbers to correlate with times of maximum upwelling and abundance of zooplankton prey in surface waters. Outside the upwelling zone in Active Pass, Bonaparte's and Mew Gulls fed mostly on fishes and intertidal organisms, but also on zooplankton along tidelines.