Some procellariiform seabirds use a dual strategy for provisioning their chicks by alternating short and long (LT) foraging trips. One of the characteristics of breeders returning from LT is the storage of oil from dietary origin in their stomach. Therefore, the objectives of our study were: (i) to characterise the stomach oil lipids of one procellariiform species breeding in Tasmania (short-tailed shearwater) and four procellariiform species breeding in the Southern Ocean (white-chinned and blue petrels, thin-billed and Antarctic prions), and (ii) to determine the potential use of these oils in studies on the feeding ecology of Procellariiformes.

Three neutral lipid classes, i.e. wax-esters, triglycerides and diacylglycerol-ethers, dominated in the 135 oil samples recovered from the five species. The use of stomach oil lipids as trophic markers was first tested with Tasmanian short-tailed shearwater, and then applied to the four other bird species. A reference collection was created gathering the majority of published lipid profiles of sub-Antarctic and Antarctic potential prey species, and the lipid profiles of five myctophid species analysed during this study. Linear discriminant analyses were subsequently performed to classify prey species, and to detect similarities between potential prey- and avian stomach oil- lipid signatures. More than 92 % of the fatty -acid and -alcohol profiles of oils showed strong associations with the lipid structure of myctophid fish, highlighting the energising importance of this fish family for the nutrition of the investigated bird species.

Stomach oil profiles also demonstrated a partial trophic segregation during LT between thin-billed prion, Antarctic prion and blue petrel (Kerguelen archipelago). The first species had mainly fed wax-ester-rich myctophid fish, the second one triglyceride-rich myctophid fish and the third one being in the middle of these two extremes. Finally, an interannual study of the blue petrel diet (combination of stomach oil and stomach content analyses) highlighted a variation of trophic relations in 2002, variation most likely related to higher sea surface temperatures which has been recorded within the same year.

We concluded that the use of stomach oil is a good tool to study the food and the feeding ecology of adult Procellariiformes during LT.