Mémoire
| Résumé : | Polar environments are particularly vulnerable to ongoing climate changes. It is essential togain a comprehensive understanding of the communities within this environment to preventsignificant population declines that could potentially lead to extinction or disruptions in thefunction or structure of ecosystem networks. Polar seabirds, being apex predators, are oftenused as bioindicators of the lower trophic levels populations dynamic. They contend with ahigh degree of environmental variability due to their extreme habitat conditions.Consequently, they have developed specific adaptations and frequently exhibit a high degreeof specialization. Alterations in resources availability or habitat could result in substantialimpacts on the biodiversity of high-latitude regions.The snow petrel (Pagodroma nivea (Forster, 1977)), a pagophilic species endemic toAntarctica, is highly reliant on sea ice dynamics. As with other seabirds, the interbreedingseason ecology of the snow petrel is understudied due to challenges in accessing them outsideof the nesting period. Stable isotope analysis is an effective ecological tool that can beemployed to investigate trophic relationships and foraging habitats across various temporalscales, depending on the tissue being analysed. The stable carbon and nitrogen isotope ratioshave been established as parameters for characterising the trophic niche of consumers. Sinceadults primary feathers are replaced during the interbreeding season (March to May) andremain metabolically inert after synthesis, their stable isotope ratios serve as a record of thetrophic niche during the molt period.In this study, we conducted sequential analyses of primary feathers from 10 adult and 13 chicksnow petrel carcasses collected at the Sør Rondane colony near the Princess ElisabethAntarctica station in the Dronning Maud Land region (Antarctica). Our findings indicate thatboth during breeding and interbreeding seasons, snow petrels forage south of the Polar Front.Adults appear to exhibit more specialized foraging behaviour during their molt, anddemonstrate more foraging flexibility during the chick-rearing period. We also identified aconsistent pattern in the sequential analysis of adult primary feathers, with more enrichedcarbon stable isotope ratios during the early phase of the molt, suggesting a foraging locationin neritic waters, and depleted ratios during the later phase of the molt indicating oceanicforaging location. This pattern aligns well with the timing of winter sea ice expansion, implyingthat snow petrels would molt in their typical foraging habitat, the pack ice area, by followingthe extension of the sea ice. |
