- Thalasseus sandvicensis
Includes Cabot's Tern and Cayenne Tern
Length 36–46 cm (14¼-18 in), wingspan 85-97 cm, weight 130-285 g
- Slender black bill with pale yellow tip
- Black legs
- Feet have yellow soles
- Light grey above with blackish wing tips. The rump and rather short forked tail are white. Underparts white (rarely faintly tinged creamy-pink).
Summer Adult: forehead, crown and nape black. Loose long feathers at the nape form a crest in the wind or when excited.
Winter Adult black areas on the front and top of the head turn white and speckled black on the crest. This can happen as early as June, more usually from July onward.
Juvenile: scalloped with blackish-brown chevrons on mantle and wings, brown on forehead, crown and nape; white elsewhere. Bill is blackish-yellow to all black.
First-winter: mantle becomes pale grey, and forehead white after post-juvenile moult in a month or two after fledging; some scalloping remains on wing coverts.
Gull-billed Tern is superficially similar in plumage, but differs structurally, with longer legs, shorter broader wings (more gull-like in flight), shorter, thicker, all-black bill, no crest, and a pale grey rump. Lesser Crested and Elegant Terns are structurally very similar, but differ in their bright orange bills, and in Lesser Crested, also a pale grey rump, and in Elegant, a longer bill. Juvenile Roseate Tern has a similar scalloped mantle pattern, but is smaller, has a darker forehead, and a longer tail.
A breeding summer visitor widely on the coasts of Europe and southwestern Asia (Estonia west to Ireland, and western France, and east through the Mediterranean from northeast Spain to the Black Sea and Caspian Sea), wintering on the west and north coasts of Africa, the Arabian Sea, and locally of western India. A separate [sub]species (see Taxonomy, below) breeds on the Atlantic coasts of North and South America, wintering additionally on the Pacific coast of northern South America.
Like the other Thalasseus terns, this species is was formerly often placed in the genus Sterna.
- Sandwich Tern Thalasseus sandvicensis sensu stricto
- Cabot's Tern Thalasseus (sandvicensis) acuflavidus
A study of genetic data showed that acuflavidus (including eurygnathus) was more closely related to Elegant Tern than to Sandwich Tern, and should be treated as separate species, Thalasseus acuflavidus. It differs from sandvicensis most obviously in a shorter, stouter bill, with in South American eurygnathus populations an increasing amount of yellow in the bill. There are also differences in timings of wing moult, and in the juvenile plumage having less scaling on the mantle. In the past, the populations with all or mostly yellow bills were sometimes treated as a separate species, Cayenne Tern T. eurygnathus, but in genetics these are very close to Cabot's Tern.
There are one or two records of transatlantic vagrants of each of T. s. sandvicensis in North America and T. s. acuflavidus in Europe; in both cases including ringed birds which allowed confirmed identification at a time when field identification between them was still poorly researched.
Almost entirely marine. Breeds on shingly, sandy or rocky islands with a high degree of protection from land predators.
Strong flight, often quite high.
Its diet includes fish which it catches by plunging into the sea.
Click on images to see full size
Sandwich Tern moulting into adult winter plumage
Photo by IanF
Newburn Bridge, Hartlepool, Cleveland, UK, October 2008
Cayenne Tern, adult
Photo by alexandre vinot
Grand Connétable, French Guiana, 4 July 2008
- Clements, J. F., T. S. Schulenberg, M. J. Iliff, D. Roberson, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2016. The eBird/Clements checklist of birds of the world: v2016, with updates to August 2016. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/
- Gill, F and D Donsker (Eds). 2016. IOC World Bird Names (version 6.3). Available at http://www.worldbirdnames.org/.
- Sangster, G., et al. (2011). Taxonomic recommendations for British birds: seventh report. Ibis 153: 883–892.
- Efe, M. A., Tavares, E. S., Baker, A. J. & Bonatto, S. L. (2009). Multigene phylogeny and DNA barcoding indicate that the Sandwich tern complex (Thalasseus sandvicensis, Laridae, Sternini) comprises two species. Mol. Phyl. Evol. 52: 263‑267.
- Garner, M., Lewington, I., & Crook., J. (2007). ldentification of American Sandwich Tern. Dutch Birding 29: 273-287.
- Neise, G. (2011). North American Birding (blog): Sandwich or Cabot's?
- Iliff, M., Grantham, M., & Garner, M. (2013). Birding Frontiers (blog): Eurasian Sandwich Tern in North America
- Collins Bird Guide ISBN 0 00 219728 6
- Handbook of the Birds of the World Alive (retrieved September 2016)
- BirdForum Opus contributors. (2021) Sandwich Tern. In: BirdForum, the forum for wild birds and birding. Retrieved 16 October 2021 from https://www.birdforum.net/opus/Sandwich_Tern