The snowy-crowned tern (Sterna trudeaui), also known as Trudeau's tern, is a species of tern in the family Laridae. It is found in Argentina, south-east Brazil, Chile, Paraguay and Uruguay, and as a vagrant in the Falkland Islands. The tern's natural habitats are swamps, shallow seas, and intertidal marshes. The species was first described by the American ornithologist John James Audubon in 1838. He had been sent a specimen by his friend Dr James de Berty