Sanderling (Calidris alba) – A Detailed Study
Taxonomy & Classification
- Kingdom: Animalia
- Phylum: Chordata
- Class: Aves
- Order: Charadriiformes
- Family: Scolopacidae
- Genus: Calidris
- Species: Calidris alba
The Sanderling (Calidris alba) is a small wading bird belonging to the sandpiper family Scolopacidae. It is a migratory shorebird, recognized for its characteristic running behavior along sandy shorelines.
Morphology & Identification
- Size: Approximately 18–20 cm in length.
- Wingspan: 30–40 cm.
- Weight: Around 40–100 grams, varying based on the season.
- Plumage:
- Breeding Season: Upperparts appear mottled with a mix of black, brown, and white.
- Non-breeding Season: Pale gray upperparts with a completely white underbelly, which gives it a very light appearance.
- Bill: Short, straight, and black, adapted for probing into wet sand.
- Legs: Black and moderately long, suited for rapid movement on coastal sands.
- Flight Characteristics: Swift and direct flight with white wing bars visible in the air.
- Distinctive Feature: Unlike many other sandpipers, Sanderlings lack a hind toe, which helps them move efficiently across sandy beaches.
Habitat & Distribution
- Global Range: Found across coastal regions worldwide, particularly during migration.
- Breeding Habitat: Arctic tundra regions of North America, Greenland, and Eurasia.
- Wintering Grounds: Migrates to coastal beaches, estuaries, mudflats, and lagoons across Europe, Africa, South Asia, and Australia.
- Preferred Environment: Open sandy shores, tidal mudflats, and salt pans.
Feeding Behavior & Diet
-
Diet Composition:
- Small crustaceans (e.g., sand fleas, amphipods).
- Mollusks and marine worms.
- Insect larvae in muddy areas.
- Occasionally scavenges on organic detritus along shorelines.
-
Foraging Strategy:
- Actively follows retreating waves to probe wet sand for prey.
- High-energy runner, continuously moving between waves.
Migration & Seasonal Movement
- One of the most migratory shorebirds, covering thousands of kilometers.
- Breeds in Arctic tundra during summer and migrates to tropical and temperate coastlines in winter.
- Major flyways include:
- East Atlantic Flyway (Europe to Africa).
- East Asia-Australasia Flyway (Asia to Australia).
- Americas Flyway (North America to South America).
Reproduction & Life Cycle
- Breeding Season: May to July.
- Nesting Grounds: Arctic tundra, often on dry, stony ground near wetlands.
- Eggs: Lays 3-4 eggs in a simple scrape nest.
- Incubation: Both parents incubate eggs for 24–27 days.
- Chick Development: Precocial chicks hatch fully feathered and are capable of feeding themselves within a day.
- Lifespan: Typically 7–10 years, but some individuals can live up to 13–15 years.
Presence of Sanderling (Calidris alba) in Sundarban
Occurrence in Sundarban
The Sanderling (Calidris alba) is a winter visitor to the Sundarban delta, an important coastal wetland in India and Bangladesh. While it does not breed here, it migrates from Arctic regions to the Indian coastline, stopping at various coastal locations, including Sundarban, during its southward journey.
Habitat Suitability in Sundarban
- Tidal Flats & Sandbars: Sanderlings prefer sandy shores, which are found in patches along the Sundarban estuaries and coastal fringes.
- Mudflats & Riverbanks: Although more commonly seen on beaches, they occasionally venture into brackish wetlands and estuarine mudflats in the Sundarban delta.
- Food Availability: The rich diversity of small crustaceans, mollusks, and polychaete worms in Sundarban makes it a good feeding ground.
Challenges for Sanderlings in Sundarban
- Habitat Loss: Rising sea levels and coastal erosion threaten suitable foraging areas.
- Disturbance: Tourism, fishing, and boat traffic can cause disruptions to their feeding and resting behavior.
- Climate Change Impact: Changes in monsoon patterns and coastal salinity may affect the availability of prey species.
Conservation Status & Protection Measures
- IUCN Status: Least Concern (LC) – but facing threats from habitat degradation.
- Legal Protection in India:
- Wildlife Protection Act, 1972 covers various migratory shorebirds.
- Ramsar Convention & Wetland Protection Programs safeguard Sundarban habitats.
- Conservation Initiatives in Sundarban:
- Monitoring migratory bird populations.
- Promoting eco-tourism with minimal disturbance to bird habitats.
- Strengthening coastal protection to prevent habitat destruction.
Conclusion
The Sanderling (Calidris alba) is a fascinating migratory shorebird that adds to the biodiversity of Sundarban during winter. Though not a permanent resident, it relies on Sundarban’s estuarine ecosystem as an essential stopover during migration. Sustained conservation efforts are crucial to ensure that these birds continue to thrive in their seasonal habitats along the Indian coastline.