South America is home to the highest diversity of birds on the planet, yet we still understand relatively little about their seasonal movements, or even which species are migratory. During two consecutive years, we used satellite transmitters to study the movement ecology of 10 individual Snail Kites (Rostrhamus sociabilis) captured in southern Brazil. We detected highly variable movement patterns among Snail Kites, with some migrating between two well-defined sites, migrating up to 4000 km to the mouth of the Amazon River. Others exhibited nomadic/facultative movements, moving different distances and to different sites between seasons and years. Overall, Snail Kites spent most of the migration period at stopover sites, moved at a higher speed, and used fewer stopovers in austral spring than in fall. These results provide the first evidence that Snail Kites in South America move across large distances, effectively connecting major watersheds, and suggest that individual Snail Kites are highly flexible in how they track resources over time and space. The complex movements and highly variable migratory behavior we detected among Snail Kites points to the need for more detailed research on the behavioral ecology and risks to survival across the annual cycle and broad range of this enigmatic and poorly understood species.

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