Multispecies Seabird Feeding Flocks in the Galápagos Islands

Abstract

I examined the species composition, frequency, distance offshore, and duration of multispecies seabird feeding flocks in the Galâpagos Islands, Ecuador. Flocks were comprised of Galâpagos Penguins (Spheniscus mendiculus), Flightless Cormorants (Campsohaelius [Nannopterum] harrisi), Brown Pelicans (Pelecanus occidentalis), Brown Noddies (Anous stolidus), Blue-footed (Sula nebouxii) and Masked Boobies (Sula dactylatra), Magnificent Frigatebirds (Fregata magnificens), and Audubon Shearwaters (Puffinus Iherminieri). Pursuit-divers, such as Galâpagos Penguins and Flightless Cormorants, increase the longevity of flocks. Species such as boobies may tend to dissipate flocks. This study provides field evidence that the presence of pursuit-diving seabirds has a positive effect on the duration of feeding flocks and that the mechanisms that keep prey close to the surface near shore may differ from those in the open ocean.