Curlew Sandpiper (Calidris ferruginea):

A Detailed Biological and Ecological Exploration

Introduction

The Curlew Sandpiper (Calidris ferruginea) is a graceful long-distance migratory shorebird, admired for its slender, downcurved bill and striking transformation between breeding and non-breeding plumages. This species occupies a prominent position among Palearctic waders due to its vast migratory journeys, specialized feeding ecology, and sensitivity to wetland health. Widely distributed across Arctic tundra breeding grounds and tropical wintering areas, the Curlew Sandpiper is a key biological indicator of coastal and estuarine ecosystems. This comprehensive article presents a research-based overview of its taxonomy, morphology, behavior, migration, ecological role, and conservation status, with special emphasis on its seasonal occurrence in the Sundarbans region.

Taxonomy & Classification

The Curlew Sandpiper belongs to the order Charadriiformes, a diverse group of birds associated with shorelines, wetlands, and open aquatic environments. Within this order, it is classified under the family Scolopacidae, which includes sandpipers, snipes, and godwits known for elongated bills and probing feeding strategies.

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

The genus Calidris encompasses several small to medium-sized sandpipers adapted to mudflat and tundra habitats. The Curlew Sandpiper is distinctive within the genus due to its longer legs, curved bill, and rusty-red breeding plumage.

Morphology & Field Identification

The Curlew Sandpiper is a medium-sized wader with an elegant silhouette. It is characterized by a long, gently decurved black bill, relatively long dark legs, and streamlined body structure. Plumage varies markedly between breeding and non-breeding seasons, aiding seasonal identification.

Male Features

During the breeding season, adult males exhibit a rich chestnut-red coloration extending from the face through the neck and underparts. The upperparts are mottled with dark brown and black feathers edged with rufous tones. The contrast between the deep red body and darker wings is particularly striking in breeding males.

Female Features

Females resemble males but tend to show slightly paler and less intense reddish coloration during the breeding season. Outside the breeding period, sexual dimorphism becomes negligible, with both sexes adopting subdued grey and white tones.

Size & Wingspan

The Curlew Sandpiper measures approximately 19–23 cm in length. Its wingspan ranges from 38–41 cm, allowing efficient sustained flight over long migratory distances. Average body weight varies between 50 and 80 grams depending on seasonal fat reserves.

Flight Characteristics

In flight, the species displays rapid, rhythmic wingbeats with brief glides. The wings appear narrow and pointed, optimized for endurance. A narrow white wing bar and pale rump are visible, assisting identification among mixed wader flocks.

Habitat & Distribution

Global Range

The Curlew Sandpiper breeds exclusively in the high Arctic tundra of Siberia. After breeding, it undertakes extensive migrations to wintering grounds across Africa, South Asia, Southeast Asia, and Australia. Its migratory routes span thousands of kilometers, crossing multiple ecological zones.

Preferred Habitat

Outside the breeding season, the species is strongly associated with coastal wetlands, estuaries, tidal mudflats, saline lagoons, and shallow inland wetlands. It shows a preference for open, muddy substrates rich in benthic invertebrates.

Diet & Feeding Ecology

The Curlew Sandpiper is predominantly carnivorous, feeding on a wide range of small invertebrates. Its diet includes polychaete worms, small crustaceans, insect larvae, mollusks, and occasionally seeds during migration stopovers.

Foraging Technique

This species employs a probing feeding strategy, inserting its curved bill into soft mud to locate prey by touch. It often feeds in shallow water or saturated substrates, moving methodically while probing repeatedly. Feeding is frequently synchronized within flocks.

Breeding & Reproduction

Breeding occurs during the brief Arctic summer, typically between June and July. Pairs form shortly after arrival on breeding grounds, and nesting begins soon after snowmelt. Both parents share incubation and chick care responsibilities.

Nesting Sites

Nests are shallow scrapes located on dry tundra ridges, often near wetlands. The nest is sparsely lined with grass or leaves. Clutches usually consist of four eggs, which are cryptically colored to blend with the tundra substrate.

Unique Adaptations & Behavioral Ecology

Speed & Agility

The Curlew Sandpiper is capable of sustained high-speed flight during migration, covering vast distances without prolonged stops. On the ground, it moves with steady precision rather than rapid bursts, conserving energy while foraging.

Camouflage and Nesting Strategy

Eggs and chicks exhibit excellent camouflage, blending seamlessly with tundra vegetation and soil. Adults rely on stillness and distraction displays to reduce nest detection by predators.

Social Behavior

Outside the breeding season, the species is highly gregarious, forming large flocks that may number in the thousands. These flocks provide increased predator detection and enhanced foraging efficiency.

Occurrence & Seasonal Movement

The Curlew Sandpiper is a classic long-distance migrant. It departs breeding grounds in late summer and reaches wintering areas by early autumn. Spring migration begins early, with birds moving northward well before Arctic snow fully recedes.

Preferred Habitat in the Sundarbans Region

In the Sundarbans, the Curlew Sandpiper is primarily a winter visitor. It is commonly observed on intertidal mudflats, estuarine banks, and shallow saline wetlands where invertebrate prey is abundant. The region’s dynamic tidal system offers ideal foraging conditions during low tide.

Ecological Role

The Curlew Sandpiper plays an important role in regulating benthic invertebrate populations within wetland ecosystems. Its presence reflects the productivity and health of intertidal habitats, making it a valuable ecological indicator species.

Habitat Alteration

Loss of intertidal mudflats, coastal development, pollution, and changes in hydrological regimes pose significant threats. Climate change and sea-level rise further exacerbate habitat loss along key migratory stopover sites.

Conservation Efforts

The Curlew Sandpiper is currently listed as Near Threatened globally due to population declines linked to habitat degradation along migratory routes. International wetland protection, monitoring programs, and sustainable coastal management are critical for its long-term survival.

Did You Know?

• The Curlew Sandpiper breeds exclusively in Arctic Siberia.
• It can migrate over 10,000 kilometers between breeding and wintering grounds.
• Its bill curvature increases slightly with age.

External Reference

Wikipedia: https://en.wikipedia.org/wiki/Curlew_sandpiper