Sternula
Sternula is a genus of small white terns. It is often subsumed into the larger genus Sterna, although the most recent changes to the AOU checklist considers it a separate genus. The genus name is a diminutive of Sterna, "tern". Species
Listed alphabetically. Saunders's and least terns were both formerly considered to be subspecies of little tern. References

 
Bird genera
Taxa named by Friedrich Boie