Unlocking the mystery of Bearded Tachuri's Polystictus pectoralis migration

AGUIAR, C. A.; ROSONI, J. R. R.; SANCHEZ, A. B.; FONTOURA, N. F.; FONTANA, C. S.

Gramado

Congreso; II Ornithological Congress of the Americas; 2023

Sociedade Brasileira de Ornitologia/Sociedad de Ornitología Neotropical/Association of Field Ornithologists

Many animals undertake regular and seasonal long-distance movements in search of optimal conditions for breeding or to find more abundant resources. Authors have suggested that the Bearded Tachuri undertakes local movements to the south of its distribution, but nothing has ever been confirmed. Here, we tested the hypothesis that the Bearded Tachuri executes migratory movements and provide evidence to support it. We searched for documented records of the species between 2001 and 2020, including scientific and citizen science data, and partitioned these records into two distinct time periods: the breeding season (November–February, n=153) and the non-breeding season (June–July, n=52). We utilized these records and relevant environmental variables for the same time period to generate environmental suitability models using the Maxent algorithm. From this set, two models were selected based on their performance as evaluated using partial ROC, AIC, and omission rate metrics and both selected models demonstrated consistency in visual analysis. In both seasons, the most important environmental variable was temperature. The selected models showed distinct environmental suitability between the reproductive and non-reproductive periods of the Bearded Tachuri, suggesting the influence of the migratory movement. Our results suggest that the species can execute latitudinal migration. Additionally, we found new evidence suggesting occurrence of altitudinal migration in populations that breed in the South Brazilian highland grasslands and spend the non-reproductive period on the southern coast of Brazil. Species distribution modeling supports migratory behavior in Bearded Tachuri, which is crucial to suggest and implementing conservation strategies.