Lesser Crested Tern vs Great Crested Tern

In short

The most reliable field mark to separate Lesser Crested Tern from Great Crested Tern is bill color: Lesser Crested Tern has a distinctly orange bill, while Great Crested Tern shows a longer, heavier bill that is yellow to greenish-yellow. Juvenile and immature birds are best separated by their upperwing and mantle patterns—Great Crested Tern juveniles are much more variegated above, with dark bars on the closed wing, while Lesser Crested Tern juveniles are paler with only faint dark crescents. In flight, Lesser Crested Tern shows a grey rump, while Great Crested Tern is darker above overall. Great Crested Tern is also noticeably larger and bulkier, but size can be hard to judge unless both are together.

Identification tips

1. Bill color is the most consistent field mark: Lesser Crested Tern has a long, sharp orange bill; Great Crested Tern has a longer, heavier bill that is yellow to greenish-yellow. This is reliable in all plumages and ages.
2. Juvenile/immature upperwing pattern: Juvenile Great Crested Tern is strongly patterned above, with dark bars on the closed wings and a variegated mantle. Juvenile Lesser Crested Tern is much paler, with only faint dark crescents on the mantle feathers and a generally cleaner look. Use this in late summer and autumn when young birds predominate.
3. Rump color in flight: Lesser Crested Tern shows a grey rump, which is a useful separator from Great Crested Tern, whose rump and tail are not as distinctly grey and whose upperparts are darker overall. This is best seen in adults and older immatures.
4. Overall upperpart tone: Great Crested Tern is darker above, with battleship-grey upperparts, while Lesser Crested Tern is paler grey above. This is more obvious in direct comparison or good light.
5. Size and structure: Great Crested Tern is about 25% larger, with a bulkier body, longer and heavier head, and a proportionately longer bill. Lesser Crested Tern is slimmer and more delicate, but size is hard to judge unless both are together.
6. Crest and forehead pattern: In breeding plumage, Great Crested Tern has a shaggier black crest and a white forehead, while Lesser Crested Tern has a full black cap. In winter, both show white on the forehead, but Great Crested Tern's crown becomes flecked or peppered with black, while Lesser Crested Tern's is more cleanly white.
7. Leg color: Both have black legs, so this is not a useful separator.
8. Bill shape: Great Crested Tern's bill is not only longer but also heavier and slightly downcurved at the tip; Lesser Crested Tern's is finer and straighter.
9. Juvenile bill color: Juvenile Lesser Crested Tern already shows a yellow-orange bill, while Great Crested Tern juveniles have a yellowish bill, but the difference is less pronounced than in adults.
10. Flight jizz: Both have long, pointed wings and a buoyant flight, but Great Crested Tern appears heavier and more powerful in flight, while Lesser Crested Tern is more agile and delicate.
11. Voice: Calls are similar—both loud and grating—but Great Crested Tern's main call is described as more raucous and crow-like. Not always reliable without experience.
12. Colony context: If seen in a mixed tern colony, check for size and bill color—Great Crested Tern will stand out as the largest, with a yellowish bill; Lesser Crested Tern will be smaller, with an orange bill.
13. Seasonal changes: In non-breeding (winter) plumage, both species develop white on the forehead, but Great Crested Tern's entire crown becomes flecked, while Lesser Crested Tern's is more cleanly white-fronted.
14. Potential confusion: Both can be confused with other orange/yellow-billed terns (e.g., West African Crested Tern, Sandwich Tern), but within this pair, focus on bill color, size, and upperpart pattern.
15. When in doubt: If the bird is large, dark above, with a yellowish bill and a white forehead (even in breeding), it's Great Crested Tern. If it's smaller, paler above, with a clean orange bill and grey rump, it's Lesser Crested Tern.

Size

Great Crested Tern is significantly larger and heavier than Lesser Crested Tern. Lesser Crested Tern averages around 209 g in body mass, while Great Crested Tern is about 325–397 g (per Wikipedia). In length, Lesser Crested Tern is 35–43 cm with an 88–105 cm wingspan, while Great Crested Tern is 46–49 cm long with a 125–130 cm wingspan. The difference is about 25% in overall size, with Great Crested Tern having a longer, heavier head and bill, and a bulkier body. However, unless seen side-by-side, this can be subtle in the field.

Plumage

Juvenile and immature birds are best separated by upperwing and mantle pattern: juvenile Great Crested Tern is strongly patterned above, with dark bars on the closed wings and a variegated look, while juvenile Lesser Crested Tern is much paler, with only faint dark crescents on the mantle feathers and a generally cleaner appearance. In adults, Lesser Crested Tern in summer has a full black cap, black legs, orange bill, grey upperwings and rump, and white underparts; in winter, the forehead becomes white. Great Crested Tern adults in breeding plumage have a shaggier black crest, white forehead (even in breeding), greenish-yellow bill, and darker, battleship-grey upperparts. In winter, Great Crested Tern becomes paler above and the crown is flecked with white. In flight, Lesser Crested Tern's grey rump is a useful mark; Great Crested Tern's rump and tail are not as distinctly grey and the upperparts are darker overall. Bill color is a key difference year-round: orange (Lesser) vs yellow/greenish-yellow (Great).

Behaviour

Both species feed by plunge-diving for fish, but Lesser Crested Tern typically dives directly, while Great Crested Tern's behavior is not described as different in the sources. Both species breed in dense colonies on coasts and islands, often in close proximity. Courtship in Lesser Crested Tern involves the male offering fish to the female. Both are highly colonial and can be seen in mixed flocks, but Great Crested Tern is more robust and may dominate in mixed groups.

Habitat

Both species are coastal and breed on islands and sandy shores, often in mixed colonies. There is significant overlap in their ranges, especially around the Indian Ocean and Mediterranean for Lesser Crested Tern, and more widely for Great Crested Tern, which is found from South Africa to Australia and the central Pacific. Habitat preference is not a reliable separator where both occur.

Voice

Lesser Crested Tern gives a loud, grating call similar to Sandwich Tern. Great Crested Tern is highly vocal, with a loud, raucous, crow-like 'kerrak' as its main call, and other harsh notes ('korrkorrkorr', 'wep wep'). Both can be noisy at colonies, but the calls are not described as reliably separable in the field.