Food of three sympatric gadfly petrels (Pterodroma spp.) breeding on the Pitcairn Islands

IMBER, M.J.; JOLLY, J.N.; BROOKE, M. de L.

Food of three sympatric gadfly petrels (Pterodroma spp.) breeding on the Pitcairn Islands

1995

IMBER, M.J. | JOLLY, J.N. | BROOKE, M. de L.

Food samples were collected from 29 Herald petrels Pterodroma heraldica, 27 Kermadec petrels P. neglecta and 37 Murphy's petrels P. ultima, on the Pitcairn Islands during 1991. 92% of samples were from chicks. Food items comprised cephalopods (in 86-92% of samples) of 22 species, fish (in 24-41% of samples) of at least four families, crustaceans (in 10-38% of samples) including mysids, an amphipod, an isopod and unidentified decapods, insects- marine water striders Halobates (in 59-66% of samples), coelenterates (in 0-8% of samples), tunicates (in 0-7% of samples), and traces of offal (cetacean or shark), plastics and pumice. Only cephalopods were sufficiendy numerous and identifiable to enable a comparison of the three petrels' diets. Herald petrels mainly fed on juvenile ommastrephids, whereas Murphy's petrels mainly ate vertically-migrating, bioluminescent cranchiids, histioteuthids and onychoteuthids; Kermadec petrels were intermediate between them. Such differences might have resulted from the different dates when, or different islands where, most samples were collected from each species; or differences in feeding ranges or times of feeding between species; or to species' preferences.

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