Light-level geolocators and species distribution modeling reveal that the Vulnerable Sporophila cinnamomea (Chestnut Seedeater) migrates through the Paraná-Paraguay system to Central Brazil.

This article focuses on elucidating the migratory routes, stopover sites, and nonbreeding areas of the Chestnut Seedeater (Sporophila cinnamomea), a vulnerable Neotropical grassland bird species breeding in southern South America. Using light-level geolocators deployed on adult males over three breeding seasons, the study identified that these birds migrate along the Paraná-Paraguay River valleys via the Central Brazil corridor to nonbreeding areas primarily within the Cerrado biome, with autumn migration involving more stopovers than spring. Species distribution modeling revealed distinct but overlapping ecological niches between breeding and nonbreeding periods, highlighting key habitat variables such as elevation, temperature, precipitation, and the presence of specific grass species important for seed availability. The findings provide critical data to inform conservation planning, emphasizing the protection of both breeding and nonbreeding habitats to support this and other threatened grassland bird species in South America.