Great Crested TernThalasseus bergiiWhere and when to see them

The greater crested tern is a large, elegant seabird of tropical and subtropical coasts across much of the Indian and Pacific oceans. Its pale yellow bill and shaggy black crest make adults distinctive on beaches and harbour structures. It depends on coastal fish and secure resting or nesting ground. In the Seychelles and Maldives, birds may be seen commuting offshore, resting on sand or joining feeding concentrations near the surface.

Size

46–49 cm long

Weight

320–400 g

Lifespan

Not reliably established

Status

Least Concern

These terns patrol coastlines with buoyant wingbeats, searching downward before dropping sharply to seize fish. They frequently rest in groups, sometimes alongside other tern species, and become noisy around breeding colonies. Courtship includes fish presentations, while nesting pairs defend small spaces within dense aggregations. Outside breeding periods, birds can disperse considerably, so a productive sandbank on one visit may be empty on another as tides and food availability change. Courtship displays often involve elaborate aerial chases and synchronized flight patterns. They are highly colonial breeders, forming dense aggregations that can number in the hundreds or thousands of pairs. After the breeding season, birds disperse widely, sometimes undertaking significant migrations across oceanic waters.

• The crest looks especially untidy when feathers are raised at the back of the head.
• Breeding adults have a black forehead, which becomes largely white outside breeding condition.
• A male may offer a fish during courtship.
• Its nest is generally a shallow scrape rather than a constructed platform.

Observation is possible throughout the year in both island groups, but local numbers change with breeding movements, weather and food. Choose calmer coastal conditions for comfortable shore or deck watching. Do not assume that a country's preferred travel months correspond to tern nesting dates. While resident, peak breeding activity in the Maldives generally occurs from May to July. In the Seychelles, breeding varies but can extend from May to September, with some local variations. Look for concentrated activity and increased vocalizations during these nesting periods.

Greater crested terns use shallow coastal waters, lagoons, reef margins and sheltered bays. They rest on beaches, sandbars, rocks and harbour structures. Breeding usually requires open, sparsely vegetated ground on islands or sandbanks where disturbance and access by terrestrial predators are limited. Greater crested terns frequently forage close to shore, making them visible from land or boat. They are often seen on exposed reefs at low tide, probing for prey. In the Seychelles and Maldives, they show a strong preference for undisturbed islets for breeding success.

Small fish dominate the diet, particularly schooling species available close to the surface. Squid and crustaceans are taken less often. Birds may exploit fish driven upward by larger predators or follow fishing activity, although such associations vary locally and are not required for feeding. They often dive from heights of 5-10 meters, plunging headfirst into the water. Parental care involves provisioning chicks with small fish for several weeks after hatching. Occasionally, they will also consume marine invertebrates like crabs and squid.

Common name

Great Crested Tern

Scientific name

Thalasseus bergii

Animal group

Birds

Size

46–49 cm long

Weight

320–400 g

Lifespan

Not reliably established

Status

Least Concern

Identification

Its large size, pale yellow bill and grey upperparts distinguish it from the smaller, orange-billed lesser crested tern and the slimmer, dark-billed common tern. Adults have a distinctive shaggy black crest that extends from the crown to the nape, giving them a 'spiky' appearance. Juveniles are mottled grey and brown, lacking the distinct black cap and showing a more uniform bill color. In flight, their long, narrow wings and shallow, fluid wingbeats are characteristic.