Distribution and migration phenology of Purple Martins (Progne subis) in Brazil

Purple Martins (Progne subis) are Neotropical migratory birds that breed across North America and spend their nonbreeding season in South America, primarily Brazil. They have been in a long-term population decline over the last five decades. There are several suggested causes for the decline, but to begin understanding the conservation needs of this species, it is necessary first to fill existing knowledge gaps about migration timing, distribution, and habitat use in Brazil. The presence of this species across most of Brazil makes it difficult to keep track of seasonal or long-term changes in its distribution without careful, widespread data collection. Citizen science offers an emerging opportunity to address knowledge gaps of roost distribution and phenology. Here, we compiled Purple Martin records from citizen science platforms, scientific collections, and bibliography to produce an overview of the distribution and phenology of the species in Brazil. It is present in most Brazilian states, but records are concentrated in the Amazon region. Previously known large roosts in southeast Brazil, especially in the state of Sao Paulo, have decreased in number of individuals over the last decade. Most records are from September to April, although phenology varies with latitude. In the equatorial region (5°N–5°S), which is crossed by all populations that come to Brazil, the number of reports shows strong temporal variation, probably related to the timing of migration in different populations.