Phenology, variation in habitat use, and daily activity patterns of Eleonora's falcon overwintering in Madagascar

Context The vast majority of the global population of Eleonora's falcon overwinters in Madagascar, where the natural environment is threatened by human-induced habitat changes, particularly intensive forest degradation. Objectives We described Eleonora's falcon phenology and habitat use based on fine-scale telemetry data and field surveys, and investigated which environmental parameters shape the observed patterns, to obtain a better insight into the species' ecological requirements during the wintering season. Methods We used high resolution GPS telemetry and remotely sensed data to establish bird-habitat associations and investigate spatiotemporal activity. We also verified habitat composition through ground surveys. Results Eleonora's falcon exploits a variety of habitats, exhibiting a distinct phenological pattern in their use. The species exhibits high site fidelity, moving progressively from more open areas towards landscapes with denser tree cover, possibly as a response to spatiotemporal patterns in food abundance. Time budget analysis revealed that Eleonora's falcon dedicates just about 15% of its daily activity to foraging, which is performed almost exclusively during daylight hours, with a greater tendency to forage at higher elevations with denser tree cover. On-site assessment of habitat composition revealed that existing habitat maps overlook small fragments of habitat and land use. However, the species' overall preference for humid forest suggests ongoing deforestation would adversely affect the availability of preferred habitat. Conclusions Our findings suggest that GPS logger technology, when combined with ground surveys, can enhance our understanding of long-distance migratory bird species' ecology at finer and more ecologically relevant scales.