WatchList Species Account for Least Tern (Sterna antillarum)

Qualifies for the list as a Red List Species


Least Terns by Greg Lavaty
Photo: Greg Lavaty

The widespread and locally common Least Tern breeds along coastal beaches and on major interior rivers in North America, where it feeds mostly on small fishes and invertebrates. The Interior and California races of Least Tern are listed as endangered.


The species winters on marine coastlines in Central and South America. For successful breeding it requires open beaches and islands where tidal or river action keeps the sites free of vegetation. It often breeds in colony sites used year after year, but can respond quickly in response to the emergence of new suitable habitat or the disappearance of old.


Least Terns will sometimes nest on flat gravel rooftops of buildings, primarily near beaches. Population sizes and colony sites can fluctuate dramatically. Its favored sites on the coast are also favored by human recreationists and developers, but it sometimes uses human-made habitats such as spoil banks, impoundments, and even bare land associated with airports.


Least Terns are vulnerable to predation by many animals, including Fish Crow, Ruddy Turnstone, grackles, herons, Great Horned Owl, Peregrine Falcon, red fox, coyote, raccoon, ghost crab, rats, and domestic cats and dogs. Predators can take up to 80% of the eggs and chicks at a colony. In the past, the bird was exploited for the millinery trade; populations also suffered from channelization and flooding behind dams and pesticides. In recent years it has rebounded due to conservation efforts. Both numbers and reproductive success should be monitored. Wherever possible, human interference should be controlled at beaches during the nesting season.