Citizen science data uncovers migratory movements of the Common Potoo, Nyctibius griseus, in Brazil

Far more complex and way less studied than the North American migratory system, Austral migratory movements are still poorly known. Part of this lack of knowledge is due the contrast between the richest world bird fauna with a few number of ornithologists in activity in the Neotropics, when compared to the northern hemisphere countries. Here we used citizen science data to detect seasonal patterns of distribution of the Common Potoo (Nyctibius griseus). This is the most widespread species of the family Nyctibiidae, and it is described as sedentary, in spite of the the absence of records in some areas during winter. We used data available from WikiAves and eBird to evaluate the seasonality in the occurrence patterns of N. griseus in distinct areas of Brazil. We removed duplicated records based on date and time, and used records of other, more abundant species as a proxy for sampling effort. We fitted 100 km side hexagons over all points and determined if they had only summer, only winter, or both summer and winter records. The results show that the southern population migrates during the winter, to places still unknown. The same seems to be true for the populations of the mountains of Minas Gerais. Our analysis shows, beyond doubt, that this species performs partial migration in Brazil, and highlights the potential of citizen science data to understand migration patterns ate broad scale.