Individual variability in habitat, migration routes and niche used by Trindade petrels, Pterodroma arminjoniana

Individual variability within a population and the eventual repeatability across time and space may provide stability in a population facing environmental changes, by affecting individuals differently. Thus, the variability and repeatability of behaviours, habitats used, niches and migratory pathways could play an important role. Trindade petrels (Pterodroma arminjoniana) are threatened seabirds that breed year round on Trindade Island in the South Atlantic Ocean, migrate to North Atlantic Ocean in the non-breeding periods, and use wide oceanic areas. This study investigated the timing, at-sea distribution, and trophic niche throughout the annual cycle of the austral fall/winter breeding group of Trindade petrel and examined consistency in distribution and trophic niche used by the Trindade petrel at the individual level, in different breeding seasons, using geolocator tracking and stable isotope analysis. Results demonstrated that petrels breed annually, maintaining their breeding schedules. Petrels share a common, vast oligotrophic oceanic area during both breeding and non-breeding periods inside the South Atlantic and North Atlantic Subtropical Gyres, respectively. Two migratory patterns were identified and used repeatedly by individuals. Although petrels overlapped at-sea distributions in consecutive breeding seasons, consistency in parameters tested was not found. Breeding in two schedules along the year, in addition to the use of different migratory pathways and flexibility in their isotopic niche can be an advantage for Trindade petrel population to cope with environmental changes. Causes and consequences of variable niche and pathways used, and the existence of consistency and variability among birds breeding later on the year remain poorly-known.