First records of migration route, phenology, and nonbreeding locations of the Desert Purple Martin (Progne subis hesperia)

Abstract Purple Martins ( Progne subis ) are long-distance migratory, aerial insectivores facing population declines, yet critical gaps remain in our understanding of the full annual cycle for all recognized subspecies. Whereas the migratory routes of the eastern ( P. s. subis ) and western ( P. s. arboricola ) subspecies have been documented, the Desert Purple Martin ( P. s. hesperia ) migratory pathway remains unknown. This study presents the first migratory records for the Desert Purple Martin, providing insights into its migratory phenology, stopover ecology, and nonbreeding range. During the 2022 and 2024 breeding seasons in Arizona, USA, we captured and equipped eleven individuals with light-level geolocators and satellite transmitters. Here, we report the migratory movements for three individuals. Two individuals migrated approximately 9000 km to the São Francisco Basin, occupying a nonbreeding region in northeastern Brazil that is spatially segregated from those reported for the other subspecies. The southbound migration was prolonged (ca. 60 days, SD ± 5) and featured multiple stopovers, particularly an extended around a 35 days (SD ± 1) stopover in western Mexico; the northbound migration was accelerated (20 days, SD ± 7). These data suggest that the desert subspecies may be geographically isolated from eastern and western lineages on its nonbreeding grounds, with its nonbreeding range centered in the semi-arid Caatinga and Cerrado biomes, regions increasingly threatened by agricultural conversion. Our findings provide essential baseline movement, habitat use, and phenological data for the Desert Purple Martin and underscore the need for subspecies-specific conservation strategies that address threats across the annual cycle.