Understanding altitudinal migration in the Atlantic Forest: a bioacoustics approach

The intratropical altitudinal migration system is the least considered in studies on bird migration in the Americas. Turdus flavipes (Turdidae) has a complex pattern of partial altitudinal migration in the Atlantic Forest, where populations that breed separately at the top and base of cliffs seem to exist, but jointly wintering at mid-altitudes. In this study, we explored the complex vocal repertoire of this species, which also mimics others, to identify a vocal identity unique to the populations from the top and base of cliffs. Once confirmed, such fact shall serve as additional evidence to confirm the existence of different breeding populations at both altitude extremes in the region. We recorded vocalizations of individuals at ~35 and ~1,100m a.s.l. We identified each note in the repertoires of each individual and classified them as exclusive or shared among individuals from each altitude. Note diversity in each area was described by the Shannon diversity index (H’). Individuals (n=6) from both sampled areas shared only 25 notes, but presented similar vocal diversity (35m: H’=3.60±0.41; 1,100m: H’=3.75±0.35). Individuals from lowland areas had 70 exclusive notes and the other 101 exclusive notes made up the repertoire of birds from the highland area. Results show apparent vocal segregation between individuals from both altitudes. Therefore, we expect that proceeding with this study we shall produce more evidences of spatial segregation of breeding populations of T. flavipes, thus allowing a more detailed understanding of the complex altitudinal migratory pattern that this species performs in the Atlantic Forest mountain range.