Sternula

{{Short description|Genus of birds}}

{{Italic title}}

{{Automatic taxobox

| name = Sternula

| image = Sternula albifrons 2 - Little Swanport.jpg

| image_caption = Little tern

| taxon = Sternula

| authority = F. Boie, 1822

| type_species = Sterna minuta{{cite web |url= https://www.aviansystematics.org/4th-edition-checklist?viewfamilies=61 |title= Laridae |author= |date= |website= aviansystematics.org |publisher= The Trust for Avian Systematics |access-date= 2023-07-26}}

| type_species_authority = Linnaeus, 1766

| subdivision_ranks = Species

| subdivision = 7, see text

}}

Sternula is a genus of small white terns, with a global distribution along sheltered sandy coasts and large rivers.

The seven species are all closely related, with similar plumage and size, all are between 22–28 cm long and 39–63 g weight. All are pale grey above, and white or very pale grey below; in all the outer primaries are darker grey (to nearly blackish), but the number of primaries that are dark varies slightly between the species. Most have a distinctive head pattern in the breeding season, with a black crown and eyeline, and a white forehead; one (fairy tern) differs in lacking the black eye line, and one (Damara tern) has a fully black crown with no white forehead in the breeding season. The legs and bill are mostly yellow (with or without a black tip) in the breeding season, but black in Damara tern. In all species the winter plumage has a more extensive white forehead, the bill is black, and the legs darker red-brown to blackish.{{cite book | last=Hoyo | first=Josep del | last2=Elliott | first2=Andrew | last3=Sargatal | first3=Jordi | title=Handbook of the Birds of the World: Hoatzin to auks | publisher=Lynx edicions | publication-place=Barcelona | date=1992 | isbn=84-87334-20-2 | page=656–659}}

Although the genus was first described in 1822 by Friedrich Boie, the species in the genus were generally retained within the larger genus Sterna, the genus that holds most terns, until a study in 2005 showed that this treatment was paraphyletic, with these seven species less closely related to typical Sterna terns, than several other terns long treated in other genera like Chlidonias and Larosterna.Bridge, E. S.; Jones, A. W. & Baker, A. J. (2005). [http://www2.hawaii.edu/~khayes/Journal_Club/summer2006/Bridge_et_al_2005_MPE.pdf A phylogenetic framework for the terns (Sternini) inferred from mtDNA sequences: implications for taxonomy and plumage evolution] {{webarchive|url=https://web.archive.org/web/20060720204025/http://www2.hawaii.edu/~khayes/Journal_Club/summer2006/Bridge_et_al_2005_MPE.pdf |date=2006-07-20 }}. Molecular Phylogenetics and Evolution 35: 459–469.

Sternula diverged early from other terns about 16 million years ago, with only the very different noddies (Anous and Gygis), and the 'brown-backed' Onychoprion terns diverging earlier.{{cite journal | last=Černý | first=David | last2=Natale | first2=Rossy | title=Comprehensive taxon sampling and vetted fossils help clarify the time tree of shorebirds (Aves, Charadriiformes) | journal=Molecular Phylogenetics and Evolution | volume=177 | date=2022 | doi=10.1016/j.ympev.2022.107620 | doi-access=free | page=107620 | url=https://www.biorxiv.org/content/biorxiv/early/2021/07/16/2021.07.15.452585.full.pdf | access-date=2025-02-22}} Despite the early origin of the genus, the current diversity within the genus is much more recent, with the species having a common ancestor around 4 million years ago. Saunders's and least terns were both formerly considered to be subspecies of little tern.

The genus name is a diminutive of Sterna, "tern".{{cite book | last= Jobling | first= James A | year= 2010| title= The Helm Dictionary of Scientific Bird Names | url= https://archive.org/details/Helm_Dictionary_of_Scientific_Bird_Names_by_James_A._Jobling | publisher= Christopher Helm | location = London | isbn = 978-1-4081-2501-4 | page = [https://archive.org/details/Helm_Dictionary_of_Scientific_Bird_Names_by_James_A._Jobling/page/n365 365]}}