Lesser Crested Tern vs West African Crested Tern

In short

The most reliable field mark to separate Lesser Crested Tern from West African Crested Tern is size and structure: West African Crested Tern is substantially larger and heavier, with a longer wingspan and a noticeably stouter, longer orange bill. Both species show similar adult plumage with black caps, black legs, and orange bills, but Lesser Crested Tern is distinctly smaller and slimmer, with a paler, more delicate bill. In flight, Lesser Crested Tern shows a grey rump, while West African Crested Tern has a white rump and tail. Juveniles of both species can be tricky, but West African Crested Tern juveniles are larger, with more variable leg color and a paler, less distinctly orange bill. Use size, bill structure, and rump color in flight as your primary separation tools.

Identification tips

1. Size is the first check: West African Crested Tern is much larger and bulkier than Lesser Crested Tern. If you see a large, heavy tern with a long wingspan, favor West African.
2. Bill structure: West African Crested Tern has a longer, stouter, and more robust orange bill; Lesser Crested Tern's bill is long but slimmer and more delicate. This is best judged with direct comparison or good views.
3. Rump and tail color in flight: Lesser Crested Tern shows a grey rump and central tail feathers, while West African Crested Tern has a white rump and tail. This is a key mark, especially in flight or when perched birds fan their tails.
4. Upperpart tone: West African Crested Tern is darker above than Lesser Crested Tern, which can look paler and cleaner in strong light.
5. Leg color in juveniles: Lesser Crested Tern juveniles have black legs; West African Crested Tern juveniles may have green, yellow, or pinkish legs, though this can be hard to see at a distance.
6. Bill color in juveniles: Juvenile Lesser Crested Tern has a distinctly yellow-orange bill, while West African Crested Tern juvenile's bill is paler yellow and smaller in proportion to the head.
7. Juvenile upperparts: Lesser Crested Tern juveniles are paler with faint dark crescents on the mantle; West African Crested Tern juveniles are more heavily streaked and blotched above.
8. Crest shape: Both have a shaggy crest in breeding plumage, but on a larger head in West African Crested Tern, making the crest look more prominent.
9. Perched jizz: Lesser Crested Tern looks slimmer, more upright, and daintier; West African Crested Tern is bulkier, with a heavier bill and more horizontal posture.
10. Flight jizz: West African Crested Tern appears more powerful and steady; Lesser Crested Tern is more agile and buoyant.
11. Seasonal context: In West Africa, both may occur, but outside this region, Lesser Crested Tern is far more likely.
12. Colony context: In mixed colonies, compare directly for size and bill thickness; Lesser Crested Tern will be noticeably smaller and slimmer-billed.
13. Primary feather wear: Both species' primaries darken with wear, so do not use this alone for separation.
14. Voice: Not reliably separable with current information; both give grating calls.
15. Habitat: Both are coastal; habitat is not a separator unless you are outside the West African range.

Size

West African Crested Tern is much larger: about 50 cm in length, with a wingspan of 125–135 cm and a mean weight of 367 g (range 320–440 g). Lesser Crested Tern is medium-large for a tern but smaller overall: 35–43 cm length, 88–105 cm wingspan, and body mass around 209 g (range 185–242 g). In mixed flocks or side-by-side, West African Crested Tern will appear bulkier, longer-winged, and heavier-billed.

Plumage

• Juveniles/Immatures: Both species have white underparts and streaked/blotched upperparts, but Lesser Crested Tern juveniles are paler overall, with only faint dark crescents on the mantle and a distinctly yellow-orange bill. West African Crested Tern juveniles are larger, with a smaller, paler yellow bill and variable leg color (not always black; can be green, yellow, or pink), and more pronounced upperpart streaking/blotching.
• Adults (Breeding): Both have black caps with shaggy crests, black legs, and long orange bills. Lesser Crested Tern has a grey rump and central tail feathers, while West African Crested Tern has a white rump and tail. Upperparts are silvery grey in both, but West African Crested Tern is overall darker above.
• Adults (Non-breeding): Both species lose some black from the forehead, but the cap remains on the crest. Bill and leg color remain diagnostic (see above).

Behaviour

Both species feed by plunge-diving for fish, typically diving directly rather than using a stepped-hover. Courtship feeding (male offering fish to female) is similar in both. Both nest in dense colonies, but West African Crested Tern is even more colonial and susceptible to mass mortality events due to disease. In flight, West African Crested Tern appears heavier and more powerful, while Lesser Crested Tern is slimmer and more agile.

Habitat

Both species are coastal and breed on islands or coasts, often in dense colonies. Lesser Crested Tern is more widespread in the Indian Ocean and Mediterranean, while West African Crested Tern is restricted to the West African coast from Mauritania to Namibia. If you are outside West Africa, Lesser Crested Tern is far more likely. Both prefer saline environments and are rarely found far inland.

Voice

Lesser Crested Tern gives a loud, grating call similar to Sandwich Tern. There is no specific description for West African Crested Tern's call in the notes, but it is likely similar to other large Thalasseus terns. Voice is not a reliable separator based on available information.