Annual movements of four South American tyrant flycatchers: uncovering intratropical migration patterns

Abstract

ABSTRACT Capsule Resident populations, and great variation in annual abundance, distance moved, and orientation of movements, were observed in four species of tyrant flycatcher. Aims To investigate the seasonal movement of four tyrant flycatcher species, classified as migrants, and to provide information on the timing of migration, migration routes, and possible environmental drivers of migration. Methods We used data from the eBird citizen science database to explore the spatial and temporal variation in the records of four tyrant flycatchers: the Lesser Elaenia Elaenia chiriquensis, Cattle Tyrant Machetornis rixosa, Swainson's Flycatcher Myiarchus swainsoni, and Rufous Casiornis Casiornis rufus. Results The Lesser Elaenia, Cattle Tyrant, and Swainson's Flycatcher showed clear seasonal movements over the year. Despite that, year-round populations were observed for the studied species throughout their distribution range. Data for the Rufous Casornis suggest a mostly resident population. Conclusions These data highlight the enormous variation in the annual movement patterns of intratropical migrants. Moreover, environmental attributes at different scales may have a strong impact on migratory behaviour in the Southern Hemisphere.