LONGITUDINAL AND CYCLIC POLEWARD MIGRATION OF A SOUTH AMERICAN INTRATROPICAL MIGRANT FLYCATCHER, THE LESSER ELAENIA (ELAENIA CHIRIQUENSIS)

Abstract

· Research on terrestrial migratory birds is incipient in Brazil. Geolocators have recently allowed tracking of small migratory passerines and such data, combined with intrinsic markers such as stable isotopes, have become invaluable in revealing migratory behavior. Here, we used data from a long-term banding program in a cerrado reserve in central Brazil, where we also deployed geolocators to track adults of a 15 g flycatcher, the Lesser Elaenia (Elaenia chiriquensis). The literature defines it as a resident or migrant that may overwinter in the Amazon or central Brazil. We combined newly collected tracking data from geolocators with long term banding data to assess the migratory connectivity of the studied population by documenting the breeding site fidelity, migratory behavior, and wintering grounds of tracked individuals. Recapture data showed that individuals lived for at least 12 years and that ~15% of all marked birds returned to a ~200 ± 185 m radius from where they were recorded in a previous breeding season. Tracking data revealed low migratory connectivity of the studied population. One individual remained resident and the other two individuals migrated through distinct routes: one made a longitudinal northeast-southwest route and the other a cyclic migration consisting of a poleward section to south Brazil, a NW flight to the Pantanal surroundings and ending with a longitudinal NE spring migration. These are the first detailed data of the migratory movements of individual Lesser Elaenias, supporting its partial rather than obligatory migration in central Brazil. Moreover, we found that migrants overwintered in savanna-like areas, as indicated by previous studies. We end by discussing a list of hypotheses we expect to guide further studies on this and other intratropical migrant species, thus contributing to improve knowledge on this complex and understudied migratory system within South America.