The number of avian species in a major wetland in north-eastern Assam has declined by almost 72% in 27 years, according to a study.

• The study focused on the Bordoibam-Bilmukh Bird Sanctuary (BBBS), located along the Dhemaji and Lakhimpur districts of Assam.

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Key Highlights of the Study on Avian Diversity at BBBS

• Sharp Decline in Avian Species: In 1997, the bird sanctuary recorded 167 avian species. The most recent study (2022-2024) found only 47 species, indicating a 71.85% decline over 27 years.
• Of the 47 bird species observed:
  • 3 species are winter migratory: Brown shrike, Citrine wagtail and White wagtail.
  • 1 summer migratory species:  Lesser kestrel
  • The remaining 43 species are resident birds.
• Causes of Decline : 
  • Anthropogenic Activities such as Overfishing, Excessive harvesting of aquatic plants and Poaching of wild birds and bird egg collection.
  • Disturbances such as use of high-decibel machines for farming near the sanctuary and conversion of the sanctuary into pastureland.
• Poached Bird Species: Lesser whistling duck, Fulvous whistling duck, White-breasted waterhen, Indian pond heron, Eastern spotted dove and Yellow-footed green pigeon.
• Environmental Impacts: Wetland degradation may lead to lowering of the water table, disruption of the food chain,decline in migratory bird populations and slowing of the nutrient cycle.
  • These changes pose threats to the ecosystem, environment, and human livelihoods.
• Call for Conservation: The study stresses the need for intense conservation efforts to restore and protect BBBS’s biodiversity.
• Biodiversity in Assam: Assam is home to about 950 bird species, including 17 endemic species.
  • The State has 55 Important Bird and Biodiversity Areas that serve as critical habitats for various avian species.

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About Bordoibam-Bilmukh Bird Sanctuary (BBBS)

• BBBS is a  small wetland located on the boundary of Dhemaji and Lakhimpur districts, Assam.
• Origin: Formed as a result of the 1950 earthquake.
• Declared a wildlife sanctuary by the Government of Assam in 1996.
• Hydrology: Initially part of the Subansiri River, a tributary of the Brahmaputra.
• The Subansiri River now flows 7 km away from the lake.
• Climate: The sanctuary experiences a moist tropical climate and receives approximately 2,000 mm of rainfall annually.
• Vegetation: Features flooded valley grasslands and wetlands.
• Fauna
• • Hosts large numbers of migratory waterfowl during winter.
  • Home to globally threatened species such as:
    • Spot-billed Pelican (Pelecanus philippensis): Near Threatened
    • Lesser Adjutant (Leptoptilos javanicus): Endangered
    • Swamp Francolin (Francolinus gularis): Vulnerable