Seasonal migration patterns of the Rufous-thighed Kite ( Harpagus diodon )

The Rufous-thighed Kite (Harpagus diodon) is an insectivorous migratory raptor that breeds in the Atlantic Forest, Cerrado, Chiquitanía, and Southern Andean Yungas and primarily overwinters in the Amazon Basin. However, the abundance and distribution in the western portion of its range—Southern Andean Yungas and Chiquitanía—remain poorly known, as well as the role of the Guianan Shield as a breeding or overwintering site. Therefore, this study integrates fieldwork, citizen science, and literature databases to clarify its seasonal patterns in these regions. I conducted foot surveys and fixed-point observations (616 h; 1,276 km) at a Southern Andean Yungas site in Argentina during the breeding and non-breeding seasons, along with large-scale road surveys in the breeding season across Bolivia’s Southern Andean Yungas, Chiquitanía, and dry Gran Chaco (75 h; 2,355 km) and Brazil’s Amazon Basin and Cerrado (249 h; 7,210 km). I found that the Rufous-thighed Kite: (1) Occurs only during the breeding season in the Southern Andean Yungas from October to March and is a complete migrant within this region, likely in the Chiquitanía as well; (2) Exhibits a low abundance during the breeding season across the Southern Andean Yungas, Chiquitanía, and dry Gran Chaco; (3) Is a widely distributed overwintering species across the western Amazon Basin from April to September; and (4) Is a rare overwintering species in the Guianan Shield, following the same annual phenology as in the western Amazon Basin. This study refines our understanding of the Rufous-thighed Kite’s annual cycle by strengthening evidence of its seasonal patterns, distribution, and abundance in the western range and the Guianan Shield.