Orange-billed tern

Orange-billed tern is a colloquial name applied to a group of four large terns in the genus Thalasseus with orange bills, which are quite similar in appearance and often considered difficult to identify, namely: The greater crested tern (Thalasseus bergii) and the Cayenne tern (Thalasseus acuflavidus eurygnathus), which have yellow rather than orange bills, are also sometimes considered part of this group.

Identification of orange-billed terns within their core ranges is straightforward.

Greater crested and Cayenne terns (which do not overlap in range) can be identified by their bill colour.

Of the truly orange-billed species, the only core range geographical overlaps are between West African crested and lesser crested terns in western Africa, and between royal and elegant terns on the west coast of the Americas; in both cases the larger size and strong bill of royal and West African crested terns should prevent misidentifications (in addition, lesser crested terns have a grey, not white, rump).

Identification of vagrants has proved to be much more difficult however, with known hybridisation, and birds which do not match the classic character sets of individual species.