Sandwich Tern - Taxonomy

Taxonomy

The terns, family Sternidae, are small to medium-sized seabirds, gull-like in appearance, but usually with a more delicate, lighter build and shorter, weaker legs. They have long, pointed wings, which gives them a fast buoyant flight, and often a deeply forked tail. Most species are grey above and white below, and have a black cap which is reduced or flecked with white in the winter.

The Sandwich Tern was originally described by ornithologist John Latham in 1787 as Sterna sandvicensis, but was recently moved to its current genus Thalasseus (Boie, 1822) following mitochondrial DNA studies which confirmed that the three types of head pattern (white crown, black cap, and black cap with a white blaze on the forehead) found amongst the terns corresponded to distinct clades. The current genus name is derived from Greek Thalassa, "sea", and sandvicensis refers to Sandwich, Kent, Latham's type locality. In birds, the specific name sandvicensis usually denotes that the species was first described from Hawaii, formerly known as the "Sandwich Islands", but the Sandwich Tern does not occur there.

This bird has three subspecies:

• T. s. sandvicensis (Latham, 1787) breeds on the Atlantic and Mediterranean coasts of Europe, and winters off western Africa and Arabia.
• The marginally smaller T. s. acuflavida (Cabot, 1847) breeds on Atlantic coasts of North America, wintering in the Caribbean and further south, and has wandered to Western Europe.
• Yellow-billed T. s. eurygnatha (Saunders 1876) (sometimes treated as a separate species, Cayenne Tern, T. eurygnatha) breeds on the Atlantic coast of South America from Argentina north to the Caribbean, intergrading with T. s. acuflavida in the north of its range.

The DNA analysis showed that Cayenne Tern differed genetically from T. s. acuflavida, but the difference not sufficient to confirm it as a definite separate species.