Stable Isotopes Confirm Community Patterns in Foraging Among Hawaiian Procellariiformes

Stable isotope analysis of whole blood was used to examine the feeding of adults and chicks of five seabirds (Wedge tailed Puffinus pacificus and Christmas Shearwiters P nativitatus Bonin Pterodroma hypoleuca and Bulwers Petrels Bulweria bulwerii and Tristram s Storm petrel Oceanodroma tristrami) in the northwestern Hawaiian Islands The goal was to compare community foraging patterns as determined by stable isotope analysis with traditional studies conducted in the early 1980s Furthermore chick rearing Procellariformes have been hypothesized to practice a bimodal food provisioning strategy a behavior yet to be documented in any of the northwestern Hawrian Islands species outside the albatrosses Except for Christmas Shearwaters adults and chicks had significantly different isotope ratios suggesting differential self and chick provisioning by adults Wedge tailed Shearwaters for aged opportunistically for themselves while providing prey of higher trophic position to their chicks Bulwer s Petrel and Tristram s Storm petrel adults likely brought prey of mote uniform trophic position to their chicks while relying on more permanent prey patches differing in composition for themselves during the bleeding season Re suits suggested little overlap in stable Isotope ratios among species and were likely a result of behavioral and morphological differences in feeding Received 12 February 2009 accepted 1 October 2009