This species breeds on the coasts of southern Peru and Espírito Santo, east-central Brazil south to Tierra del Fuego, Argentina and Chile, and the Falkland Islands (Malvinas) (Duffy et al. 1984, Schlatter 1984, Woods 1988, De Tarso Zuquim Antas 1991). In the austral winter, most birds breeding in the extreme south move north to Uruguay (where breeding remains unconfirmed), and the species also winters north to Ecuador and Bahia, Brazil (Antas 1991). There are also large colonies on inshore islands in Guanabara Bay and off the Espírito Santo coast, Brazil (Antas 1991). The population on the Falkland Islands was recently estimated at 6,000-12,000 pairs (Woods and Woods 1997), and a colony exceeding 1,000 pairs was discovered in south Peru in 1995 (del Hoyo et al. 1996), where it is fairly common (Clements and Shany 2001). However, although formerly locally common in Chile, only two breeding sites are now known (Damas Island and Inutil Bay near Porvenir), and extensive searches to locate former colonies between 1994 and 1997 were unsuccessful (Mickstein in litt. 1998).
: International Union for Conservation of Nature and Natural ResourcesBibliographic Citation
: BirdLife International 2012. Sterna hirundinacea
. In: IUCN 2014 . IUCN Red List of Threatened Species. Version 2014.1 . <www.iucnredlist.org