Lesser Crested Tern (Thalasseus bengalensis) – A Detailed Study

The Lesser Crested Tern (Thalasseus bengalensis) is a medium-sized seabird belonging to the family Laridae. It is widely distributed along coastal regions, islands, and estuaries, including the Sundarban ecosystem. This species plays an important role in maintaining the ecological balance of marine and estuarine environments.

1. Taxonomy & Classification

• Kingdom: Animalia
• Phylum: Chordata
• Class: Aves
• Order: Charadriiformes
• Family: Laridae
• Genus: Thalasseus
• Species: T. bengalensis

This bird is closely related to other tern species such as the Greater Crested Tern (Thalasseus bergii) and the Sandwich Tern (Thalasseus sandvicensis).

2. Morphology & Identification

The Lesser Crested Tern is a striking seabird with distinct features that help in its identification:

• Size: Medium-sized tern, typically 32-36 cm in length with a wingspan of 85-95 cm.
• Weight: Around 200-300 grams.
• Plumage: Light grey upperparts, white underparts.
• Crest: A prominent black crest on its head during the breeding season.
• Bill: Orange to reddish-orange, slender, and slightly curved.
• Legs: Black and relatively short.
• Wings: Long and pointed, well-adapted for fast and agile flight.

In non-breeding plumage, the black cap becomes less pronounced, appearing more mottled with white.

3. Habitat & Distribution

The Lesser Crested Tern is primarily found along coastal areas, estuaries, and islands. It prefers:

• Tropical and subtropical coastal waters
• Mangroves and estuarine regions
• Sandy beaches and rocky shores
• Coral reefs and lagoons

Global Distribution:

This species is distributed across the Indian Ocean, Red Sea, Persian Gulf, Arabian Sea, Bay of Bengal, and coastal areas of Africa, South Asia, and Australia.

Presence in Sundarban:

The Sundarban, with its vast network of estuaries, mangroves, and tidal flats, provides an ideal habitat for the Lesser Crested Tern. It is commonly observed:

• Near mudflats and sandbanks, where it forages for fish.
• Around open waters of the delta, where large fish schools attract seabirds.
• In coastal breeding colonies, although they prefer offshore islands for nesting.

This species is a seasonal visitor to the Sundarban, especially during migration periods.

4. Feeding Behavior

The Lesser Crested Tern primarily feeds on small fish, which it catches through aerial dives into the water.

• Primary Diet: Small pelagic fish, crustaceans, and cephalopods.
• Hunting Technique:
  • Soars over water with rapid wingbeats.
  • Dives sharply to capture fish just below the surface.
  • Occasionally follows fishing boats to scavenge discarded fish.

Its feeding habits are essential in maintaining the marine food chain, balancing fish populations.

5. Breeding & Nesting

• Breeding Season: Typically from April to July, depending on location.
• Breeding Sites: Prefers offshore islands, sandy beaches, and undisturbed islets.
• Nesting Habits:
  • Colonial breeder, nesting in large groups.
  • Builds shallow scrapes on the ground, often on sand or gravel.
  • Lays one or two eggs, which are incubated for 21-25 days.
  • Both parents share incubation and feeding duties.

Chicks are semi-precocial, meaning they hatch with some mobility but rely on parents for food.

6. Special Features & Adaptations

• Efficient Flight: Long, pointed wings provide excellent aerodynamics, enabling fast flight and sharp dives.
• Coloration Camouflage: The grey and white plumage helps blend into the marine environment, avoiding predators.
• Highly Social: Forms large colonies during breeding, providing protection from predators.
• Adaptability to Saline Environment: Can excrete excess salt through specialized salt glands, allowing it to survive in marine habitats.

7. Conservation Status & Threats

• IUCN Status: Least Concern (LC) – The global population is stable, though local threats exist.
• Major Threats:
  • Habitat destruction due to coastal development.
  • Disturbance from human activities like tourism and fishing.
  • Pollution – Plastic and oil spills harm feeding grounds.
  • Climate change – Rising sea levels threaten nesting sites.
  • Overfishing – Reduces the availability of prey species.

Conservation Efforts in Sundarban:

• Protected Areas: The Sundarban Biosphere Reserve offers some protection to these birds.
• Mangrove Conservation: Efforts to preserve mangrove forests indirectly benefit the Lesser Crested Tern.
• Eco-Tourism Regulations: Restricted tourism zones help minimize human disturbance.

8. Role in the Sundarban Ecosystem

The Lesser Crested Tern is an important bio-indicator in the Sundarban ecosystem.

• Controls Fish Population: By preying on small fish, it helps maintain ecological balance.
• Supports Biodiversity: Provides food for larger predators like raptors.
• Indicator of Marine Health: Changes in its population reflect the health of coastal and marine ecosystems.

Conclusion

The Lesser Crested Tern (Thalasseus bengalensis) is a remarkable seabird with vital ecological roles. While it is not currently endangered, coastal habitat destruction and climate change pose challenges to its long-term survival. Protecting the Sundarban and its delicate estuarine ecosystem is crucial to ensuring that this species continues to thrive in the region.

By promoting sustainable tourism, habitat conservation, and reducing pollution, we can safeguard not only the Lesser Crested Tern but the entire biodiversity of the Sundarban.