Thick-billed Green Pigeon (Treron curvirostra) – A Comprehensive Study

Taxonomy & Classification

• Kingdom: Animalia
• Phylum: Chordata
• Class: Aves
• Order: Columbiformes
• Family: Columbidae
• Genus: Treron
• Species: Treron curvirostra

The Thick-billed Green Pigeon (Treron curvirostra) is a fascinating member of the Columbidae family, which includes pigeons and doves. It is known for its vibrant green plumage and specialized frugivorous diet. This species plays a vital role in seed dispersal within forest ecosystems.

Morphology & Physical Description

• Size: 25–27 cm in length
• Wingspan: Approximately 40 cm
• Weight: 130–190 grams
• Plumage:
  • Males: Green body with a yellowish tinge, a maroon-brown mantle, and a greyish head.
  • Females: Generally more uniform green, lacking the maroon coloration.
• Bill: Thick, short, and curved, with a bluish or greyish base and pale greenish tip.
• Eyes: Distinctive red or orange orbital ring.
• Legs & Feet: Short, sturdy, and reddish.
• Tail: Medium-length, with a slight notch at the center.

Habitat & Distribution

The Thick-billed Green Pigeon inhabits dense forests, mangroves, and tropical lowland regions across Southeast Asia and parts of the Indian subcontinent. It prefers:

• Evergreen and semi-evergreen forests
• Mangrove swamps and riverine forests
• Fruit-bearing trees in dense canopies

Presence in the Sundarban

The Sundarban, with its dense mangrove forests and rich floral diversity, provides an ideal habitat for the Thick-billed Green Pigeon. Key areas where this species is found include:

• Mature mangrove trees with abundant fruiting species (e.g., Sundari, Goran, and Gewa trees)
• Riverbanks and estuarine islands where fig and fruiting trees are present
• Mixed-forest patches within the Sundarban Biosphere Reserve

Though not as common as other pigeon species, the Thick-billed Green Pigeon is an important part of the Sundarban’s ecosystem, contributing to seed dispersal and forest regeneration.

Feeding Behavior & Diet

• Diet: Primarily frugivorous, consuming:
  • Figs, berries, and soft fruits
  • Seeds and buds
  • Occasionally, nectar from flowers
• Foraging Behavior:
  • Feeds in small flocks, often in the mid to upper canopy
  • Uses its strong, curved bill to pluck and crush fruit
  • Swallows fruit whole, aiding in seed dispersal across forests

Breeding & Nesting

• Breeding Season: Primarily from March to June, though some variations occur depending on location.
• Nest: A simple, loosely constructed platform of twigs, usually placed in dense foliage.
• Eggs: Typically one or two white eggs per clutch.
• Incubation Period: Around 14–17 days, with both parents sharing incubation duties.
• Chick Development: Hatchlings are altricial (born helpless), relying on “pigeon milk” secreted by both parents for nourishment.

Vocalization & Communication

The Thick-billed Green Pigeon is relatively silent, but its calls include:

• Soft cooing sounds, often repeated in a rhythmic pattern.
• A low-pitched “hoo-hoo-hoo”, used for communication within flocks.

Special Adaptations

1. Cryptic Coloration: Its green plumage helps it blend into dense foliage, protecting it from predators like hawks and snakes.
2. Strong Beak & Digestive System: Allows it to swallow large fruits whole, aiding in seed dispersal.
3. Arboreal Lifestyle: Adapted for tree-dwelling, with strong feet for gripping branches.
4. Efficient Flyer: Though mainly canopy-dwelling, it is a strong flyer, capable of covering long distances in search of food.

Threats & Conservation Status

• Habitat Loss: Deforestation and mangrove destruction threaten its population.
• Hunting & Poaching: In some areas, pigeons are hunted for food.
• Climate Change: Rising sea levels and extreme weather events affect the Sundarban ecosystem, impacting food availability.
• Pesticides & Pollution: Affect the fruit-bearing trees on which this species depends.

IUCN Status: Least Concern (LC)

Despite being listed as Least Concern, localized populations are declining due to habitat degradation. Conservation of mangrove forests and reducing human disturbances in the Sundarban are vital to ensuring its continued presence.

Conclusion

The Thick-billed Green Pigeon (Treron curvirostra) is an essential part of tropical and mangrove ecosystems, including the Sundarban. Its role in seed dispersal contributes to forest regeneration, making it a keystone species for maintaining biodiversity. Conservation efforts must focus on protecting its habitat and ensuring sustainable forest management to support its populations in the Sundarban Biosphere Reserve.