Tracking tiny migrants: first description of the annual cycle of Sporophila seedeaters

Neotropical seedeaters are an emblematic and threatened grassland species of South America. The tropeiro seedeater (Sporophila beltoni) is a newly described migrant species that breeds at temperate latitudes and overwinters at tropical latitudes in South America. We still know very little about its annual cycle, including its winter range, migratory timing, and routes. To address this, we tracked two males, a first-year and an adult, throughout one complete migration cycle, using light-level geolocators. The adult and first-year male departed from the breeding site region in southern Brazil in early March, migrating northwards on fall migration for 25 and 26 days, respectively. The overwintering period lasted 195 (adult) and 225 days (first-year) during which they used four winter sites each, in the Cerrado biome. Both males started spring migration the following October to early November, which lasted about 40 days, with the younger male making four stops during spring migration. The adult and first-year males we tracked made a round-trip of 3560 and 3170 km, respectively. Our findings provide the first description of migratory routes of a Neotropical seedeater throughout its full annual cycle and highlight the importance of understanding the annual cycle of tiny migratory songbirds, which will help improve conservation planning for these species.