Sooty Tern: where and when to see them

The sooty tern is a highly oceanic tropical seabird with sharply contrasting black upperparts and white underparts. It spends much of its life far from land, returning to low islands to breed in dense, noisy colonies. Its long wings and deeply forked tail suit sustained flight over warm seas. Although globally widespread, its dependence on a limited supply of safe nesting islands makes individual colonies vulnerable to introduced predators, disturbance and coastal change.

Size

33-36 cm long

Weight

150-250 g

Lifespan

Not reliably established

Status

Least Concern

Sooty terns search for prey in flight, often joining other seabirds above feeding predatory fish that drive small prey toward the surface. They generally pick food without settling on the water. At colonies, adults call almost continuously, defend small nest spaces and locate their partners or chicks amid intense crowding. Breeding can be highly synchronized locally, but schedules differ among islands and may not follow the same annual pattern everywhere. Sooty terns exhibit highly communal breeding, forming some of the largest and densest seabird colonies in the world, sometimes numbering millions of individuals. Their vocalizations are a prominent feature of colonies, producing a continuous, high-pitched 'wide-awake' or 'ker-wack-wack' call. Adults feed their chicks regurgitated fish, returning to the colony after foraging trips that can extend for many days.

• Its loud colony calls inspired the traditional English name wideawake.
• A clutch normally contains only one egg.
• Breeding colonies can contain hundreds of thousands of birds.
• Some populations breed on cycles shorter than a calendar year.

In Seychelles, roughly May through September can overlap major colony activity at some sites, subject to local management and annual variation. In the Maldives, species-specific shore-viewing seasonality is poorly supported; favorable travel weather alone should not be presented as a reliable tern window. In the Seychelles, the specific timing of breeding colonies can vary by island and year, but the general window of May to September offers the highest likelihood of observing active sites. While not strictly seasonal for shore viewing in the Maldives, the dry, calmer season from December to April generally provides more comfortable conditions for boat excursions and potentially better visibility for distant observations. Cruise itineraries should consider local conservation efforts and regulations regarding colony visits.

Open tropical and subtropical seas dominate its life away from breeding. Colonies occupy flat sandy, coral or rocky islands with open ground or low vegetation. Suitable nesting land must be relatively free of terrestrial predators and protected from excessive disturbance and tidal flooding. This pelagic species spends much of its life at sea, often hundreds of kilometers from land, only returning to land to breed. Nesting islands are typically remote, low-lying coral atolls or cays, offering protection from human disturbance and larger land predators. Breeding sites often have sparse vegetation that provides minimal shade for chicks.

Small fish and squid form most of the diet, with some crustaceans also taken. Prey is usually seized at or just above the sea surface. Associations with tuna and other marine predators help make otherwise inaccessible schooling prey available to these aerial hunters. Sooty terns are surface feeders, not plunge divers; they snatch prey from the water's surface or just above it. Their diet primarily consists of small, schooling pelagic fish like anchovies and juvenile tuna, along with squid. They forage opportunistically, often associating with active tuna schools and other larger predators that drive prey upwards.

Common name

Sooty Tern

Scientific name

Onychoprion fuscatus

Animal group

Birds

Size

33-36 cm long

Weight

150-250 g

Lifespan

Not reliably established

Status

Least Concern

Identification

Compared with bridled tern, it has darker, less gray upperparts and a white forehead patch that does not extend as a long white stripe behind the eye. Key identification features include their entirely dark sooty brown upperparts, contrasting sharply with clean white underparts and a distinctive white forehead patch. The flight pattern is characterized by long, graceful glides followed by several quick, shallow wingbeats. Their long, deeply forked tail is also a good distinguishing feature in flight.