Dunlin (Calidris alpina)

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**Dunlin (Calidris alpina) – A Detailed Study**

The Dunlin (Calidris alpina) is a small but fascinating shorebird belonging to the sandpiper family. This species is widely distributed across the Northern Hemisphere, especially in coastal regions. Below is an in-depth analysis of its taxonomy, morphology, habitat, behavior, and its presence in the Sundarban ecosystem.

1. Taxonomy & Classification

Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Scolopacidae
Genus: Calidris
Species: Calidris alpina

The Dunlin is a member of the diverse sandpiper family (Scolopacidae), which includes various shorebirds that inhabit coastal and wetland ecosystems.

2. Morphology & Physical Description

Size: 16–22 cm in length
Wingspan: 32–40 cm
Weight: 40–75 grams
Bill: Medium-length, slightly downward-curved
Legs: Dark-colored, moderately long
Plumage:
- Breeding Season: Reddish-brown upperparts with a distinctive black belly patch
- Non-breeding Season: Grayish-brown plumage with a paler underside
Eyes: Small, dark, and alert

Dunlins are known for their seasonal plumage variation, which helps them blend into different environments throughout the year.

3. Habitat & Distribution

Dunlins inhabit coastal mudflats, estuaries, marshes, and shorelines. Their geographical range covers:

Breeding Grounds: Arctic and subarctic regions of North America, Europe, and Asia
Wintering Areas: Southern coastal regions, including India, Africa, and parts of Southeast Asia

They prefer intertidal zones, where they forage for food in the wet sand.

4. Feeding & Diet

Dunlins primarily feed on:

Invertebrates like insects, mollusks, and small crustaceans
Marine worms and annelids
Occasionally seeds and plant material

They have a probing feeding behavior, using their slightly curved bill to dig into the mud in search of prey.

5. Migration Pattern

Dunlins are highly migratory and travel thousands of kilometers between their breeding and wintering grounds. Some key migration facts:

They follow coastal flyways during migration.
Many populations travel from the Arctic to temperate and tropical regions.
They form large flocks during migration, offering protection from predators.

6. Behavior & Adaptations

Flocking Behavior: They often move in synchronized formations, especially when avoiding predators.
Seasonal Molt: They change plumage based on the season to enhance camouflage.
Foraging Adaptation: Their sensitive bill tip helps detect prey buried in the sand.

Dunlins are highly gregarious in winter, often seen in mixed groups with other waders.

7. Breeding & Reproduction

Breeding Season: May to July
Nesting:
- Ground nest in tundra or coastal marshes
- A shallow depression lined with grass and moss
Eggs: 3–4 eggs per clutch
Incubation Period: ~20–22 days
Parental Care:
- Both parents incubate eggs.
- The female may leave early, leaving the male to care for the chicks.

Chicks are precocial, meaning they can walk and feed themselves soon after hatching.

8. Predators & Threats

Natural Predators: Falcons, hawks, foxes, and larger shorebirds.
Environmental Threats:
- Habitat destruction due to coastal development
- Climate change, affecting breeding grounds
- Pollution in wetland areas
Conservation Status: Least Concern (LC) (IUCN Red List), but habitat degradation is a growing concern.

9. Presence of Dunlin in Sundarban

Is Dunlin Found in the Sundarban?

Yes, Dunlins (Calidris alpina) have been observed in the Sundarban delta, though they are not a resident species. They are seen as winter visitors, arriving in the region during migration.

Why is Sundarban Important for Dunlins?

The Sundarban Biosphere Reserve, with its extensive mudflats, estuaries, and intertidal zones, provides an excellent wintering ground for migratory shorebirds, including the Dunlin. The nutrient-rich waters attract a variety of small invertebrates, which form the bird’s primary diet.

Key Observations in Sundarban

Dunlins are most commonly sighted from November to March.
They are often seen foraging along mudflats and shallow waters.
They may mingle with other migratory shorebirds such as sandpipers, plovers, and godwits.
The tidal ecology of the Sundarban plays a crucial role in their survival by maintaining a rich prey population.

Threats in the Sundarban

Despite being a safe stopover, the Sundarban ecosystem faces several challenges:

Rising sea levels could reduce the available mudflat area.
Pollution & siltation from upstream activities affect water quality.
Disturbance from human activities, including tourism and fishing, may impact their foraging behavior.

Conservation in Sundarban

The Sundarban Reserve Forest is under protected status, which helps safeguard the delicate mudflat and estuarine habitats. Additionally:

Eco-tourism guidelines ensure minimal disturbance to migratory birds.
Birdwatching initiatives help in monitoring the presence and numbers of Dunlins in the region.
Wetland conservation programs are crucial in maintaining the food-rich habitat.

10. Conclusion

The Dunlin (Calidris alpina) is an impressive migratory shorebird, well-adapted to coastal ecosystems. Its ability to travel great distances and thrive in mudflats and estuaries makes it an important part of wetland biodiversity. While it is not a resident of Sundarban, its presence as a winter migrant highlights the richness of the Sundarban delta as a crucial stopover for migratory birds. Conservation efforts must continue to ensure that vital habitats like the Sundarban remain thriving ecosystems for birds like the Dunlin.