Fatty acid signatures of stomach contents reflect inter- and intra-annual changes in diet of a small pelagic seabird, the Thin-billed prion Pachyptila belcheri

In diet analyses of seabirds, fatty acid signatures (FAS) can be used to overcome biases due to differential digestion of prey and enable the analysis of very digested diet samples. We applied FAS analysis to stomach contents of a small sub-Antarctic seabird, the Thin-billed Prion Pachyptila belcheri, which feeds mainly on squid during incubation and on crustacea during chick rearing . This seasonal dietary switch of Thin-billed prions was reflected in differences in FAS in regurgitates, as were inter-annual differences in diet composition. A discriminant function analysis correctly classified 93.4% of cases with respect to year (2006 2008) and stage of the breeding cycle (incubation versus chick rearing). The dominant types of crustacea in the diet of Thin-billed prions (amphipods Themisto gaudichaudii, euphausiids, decapods Munida gregaria, and calanoid copepods) were distinguished well by characteristic FAS patterns. However, the FAS of the two main types of prey by volume, amphipods T. gaudichaudii and squid Communicated by S. Garthe. Electronic supplementary material The online version of this atticle (doi : 10.1007/s00227 Oil 16938) contains supplementary material, which is available to authorized users. P. Quillfeldt (121) . J. F. Masella Max Planck Institut fUr Ornithologie, Vogelwarte Radolfzell, Radolfzell, Germany email: [email protected] P. Brickle Fisheries Department, Falkland Islands Government, Directorate of Natural Resources, P.O. Box 598, Stanley, Falkland Islands D. Martin Creuzburg Limnologisches Institllt, Universitat Konstanz, Konstanz, Baden WUrttemberg, Germany Gonatus antarcticus, were similar to each other. Although FAS were successfully applied in the analysis of prey in stomach contents of prions, FAS of some prey species were similar and may not be distinguishable from each other if used in quantitative diet analyses.