High Quality Content by WIKIPEDIA articles! The Caspian Tern (Hydroprogne caspia, formerly Sterna caspia;syn. Hydroprogne tschegrava) is a species of tern, with a subcosmopolitan but scattered distribution. Despite its extensive range, it is monotypic of its genus, and has no subspecies accepted either. In New Zealand it is also known by the Maori name Taranui.