Sternula antillarum (MPR):breeds from April to July on the east coast of the USA, it migrates to the Caribbean and South America, and overwinters mainly in Brazil (Gochfeld & Burger, 1996) according to data from two individuals banded in the USA and recovered in AL in January (Olmos, 2002a). However, there is a breeding colony on Curupu Island/MA monitored between May and July (Rodrigues et al., 2010) that suggests that there are possibly two populations in Brazil and their limits are not yet known. This way, occurrence data in Brazil may include birds both from the Brazilian populations and migrants from the Northern Hemisphere. There are records for AP between October and April (Xavier & Boss, 2011; WikiAves, 2016) that are probably individuals from North America, and for PA between May and October (Valente, 2011; WikiAves, 2016; MPEG) that would belong to the Brazilian population. In the Northeast region, there are records or BA (Lima, 2006), PE (Azevedo-Júnior & Larrazábal, 2011a), SE and AL (Azevedo-Júnior & Larrazábal, 2011b), from September to May (WikiAves, 2016; MZUSP), which suggests that these are records of the north population. Records for CE, RN (Girão et al., 2008; Albano & Girão, 2011; Girão & Albano, 2011a) and MA are distributed in all months of the year (WikiAves, 2016), which suggests that there is an overlap of migratory and resident individuals. In RS, records are probably of migrants and from November to April (WikiAves, 2016).