The foraging ecology of Peruvian seabirds.

Most feeding by seabirds in the Peruvian Coastal Current, an upwelling of high productivity off the west coast of South America, takes place in groups. The major prey is an anchovy Engraulis ringens, which occurs in large shoals and is exploited mainly by Peruvian booby Sula variegata, Peruvian brown pelican Pelecanus occidentalis thagus and Guanay cormorant Phalacrocorax bougainvillii. Other foraging situations have different species' compositions; these appear to be related to the size, depth, and duration of availability of prey. Dominance interactions between species may be important in structuring flocks that are scavenging or feeding on plankton swarms. Interspecific piracy seems unimportant in flocks foraging on fish shoals. Certain species usually arrive first at new feeding situations. These species may be used as guides by other species or merely may be faster and thus reach food sources first.-from Author