114 3.3 Environmental and anthropogenic drivers of nesting site selection Geographical characteristics, exposures to anthropogenic disturbance and geomorphological profiles of the surveyed islets were inferred from available sources or reported from field observations to test their respective influence over the number of nests at the scale of the GLS. Two distinct but complementary spatial frameworks of nesting site selection were considered. First to the inter-islet scale, by characterizing the impact of general geographic features and levels of exposure to human activities upon the predicted seasonal number of nests (‘nest_islet_median’). Second to the habitat scale, through the assessment of geomorphological characteristics’ influence upon the predicted sector number of nests (‘nest_sector_median’). 3.3.1 Islet geographical features and exposure to anthropogenic disturbances The geographical extent and features of each surveyed islet were calculated from analytical algorithms provided by QGIS (version 3.34.3) and the New Caledonian Government public satellite data, freely available at https://data.gouv.nc/explore/dataset/limites-administrativesterrestres/information/. For each islet, we characterized the total perimeter length (‘perimeter_tot’), the perimeter length of accessible coastline segments to sea turtles (thus excluding rocky cliffs and outcrops) (‘perimeter_fav’), the total surface area (‘surface’), and its distance to the closest reef-pass (‘dist_reefpass’). Moreover, an index of the erosion dynamic (‘erosion_index’) was defined based on the methodology used by Garcin et al. (2016), ranging from 1= growth stage to 5= decay stage, and implemented through the reconstruction of shoreline changes in the islet over the last decades (Table 14 SI Appendix). As direct data on the nature and level of anthropogenic disturbances were lacking, especially the seasonal number of visitors, indicators were approximated based on the islets’ distance to human settlements and observed evidence of human use reported during our field surveys. For each surveyed islet, we assessed the distance to the capital city of Nouméa (‘dist_noumea’) and the distance to the closest harbor (‘dist_harbor’), based on the New Caledonian Government public satellite data. During field surveys, we also recorded the number of boats anchored around the islets (‘boats_index’), the number of fire camp remains (‘firecamps_index’), and the number of visitors encountered on the perimeter of the islet (‘visitor_index’). As the survey of these parameters only occurred from the 2020-21 to the 2022-23 nesting seasons, and considering that the distribution and intensity of the islets human
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