Slender‐billed Gull (Chroicocephalus genei) – A Comprehensive Overview

The Slender-billed Gull (Chroicocephalus genei) is a fascinating species of gull that exhibits unique morphological and behavioral traits. It is an important bird in wetland and coastal ecosystems, including parts of the Sundarban delta. Below is a detailed analysis of its taxonomy, morphology, habitat, diet, breeding behavior, special features, conservation status, and its presence in the Sundarban ecosystem.

1. Taxonomy & Classification

• Kingdom: Animalia
• Phylum: Chordata
• Class: Aves
• Order: Charadriiformes
• Family: Laridae
• Genus: Chroicocephalus
• Species: C. genei

The Slender-billed Gull was previously classified under the genus Larus but has now been placed under Chroicocephalus based on phylogenetic studies.

2. Morphology & Physical Description

The Slender-billed Gull gets its name from its characteristic thin and elongated bill, which sets it apart from other gull species.

Key Morphological Features:

• Size: Medium-sized gull, measuring 37–40 cm in length
• Wingspan: Ranges from 90–110 cm
• Weight: Around 250–350 g
• Bill: Long, slender, slightly curved downward, pinkish to reddish in color
• Plumage:
  • Adults have pale gray upperparts and white underparts
  • The head is whitish in non-breeding plumage and slightly darker with a faint hood in breeding season
  • Juveniles have a brownish tinge on their upper wings
• Legs & Feet: Pink to reddish, well-adapted for wading
• Eyes: Dark with a distinct, expressive appearance

This bird’s slender bill, lightweight body, and long wings make it a graceful flier with strong foraging abilities.

3. Distribution & Habitat

The Slender-billed Gull is found in a variety of coastal and wetland environments across Europe, Africa, and Asia. It prefers shallow coastal waters, estuaries, salt pans, and large inland lakes.

Geographical Distribution:

• Europe: Mediterranean regions (Spain, France, Italy, Greece)
• Africa: Northern Africa, including Tunisia, Egypt, and parts of West Africa
• Asia: Middle East, Pakistan, India, Bangladesh, Sri Lanka, and extending to China

Preferred Habitat:

• Coastal lagoons and mudflats
• Salt marshes
• Mangrove regions
• Large inland lakes with shallow water
• Estuarine zones

4. Diet & Foraging Behavior

The Slender-billed Gull is an opportunistic feeder, primarily consuming:

• Small fish (major part of its diet)
• Crustaceans (shrimps, crabs, amphipods)
• Aquatic insects (larvae, midges, and flies)
• Plankton & organic debris from water surfaces

Foraging Strategy:

• Skims the water surface with its thin bill
• Dives occasionally to catch small fish
• Feeds in small groups but can form large flocks in resource-rich areas

5. Breeding & Nesting

The Slender-billed Gull breeds in colonies, often in association with other gull and tern species.

Breeding Season:

• Varies across regions but mainly occurs from March to June

Nesting Behavior:

• Nests on: Flat sandy islands, salt flats, and marshes
• Nest Type: Shallow scrapes lined with vegetation
• Eggs: Usually 2–3 eggs, pale in color with brown speckles
• Incubation: 22–25 days, both parents share duties
• Chick Development: Hatchlings are semi-precocial and start wandering near the nest soon after hatching

6. Special Features & Adaptations

• Unique Slender Bill: Unlike other gulls, it has a long, thin bill perfectly adapted for surface-skimming feeding.
• Light Body & Long Wings: Makes it highly maneuverable in flight.
• Colonial Breeding: Ensures better survival against predators.
• Seasonal Migration: Moves between breeding and wintering sites, often over long distances.

7. Conservation Status & Threats

IUCN Red List Status: Least Concern (LC)

Although its population is stable, some threats include:

• Habitat loss due to coastal development
• Pollution (plastic waste, oil spills)
• Overfishing, reducing its primary food sources
• Disturbance in breeding colonies from human activities

8. Presence in the Sundarban

The Sundarban mangrove ecosystem provides an important habitat for various migratory birds, including the Slender-billed Gull.

Occurrence in the Sundarban:

• Mostly seen during winter months as a migratory species
• Found in coastal mudflats, riverbanks, and estuaries
• Often observed in small groups or mixed with other waders

Importance in the Sundarban Ecosystem:

• Helps in controlling fish and insect populations
• Plays a role in nutrient recycling within the wetland ecosystem
• Acts as a bio-indicator for environmental changes, as it is sensitive to habitat degradation

Challenges in the Sundarban:

• Rising sea levels and climate change affecting its feeding grounds
• Industrial and plastic pollution threatening food availability
• Disturbance due to boat traffic and tourism in critical habitats

9. Conclusion

The Slender-billed Gull (Chroicocephalus genei) is a distinctive gull species with its elegant, thin bill and preference for coastal wetlands. While it thrives in diverse habitats across Europe, Africa, and Asia, it also finds refuge in the Sundarban, where it plays a vital ecological role. Although currently not threatened, conservation efforts should focus on protecting wetland habitats to ensure the survival of this graceful migratory bird.