In News:

A recent study has revealed a dramatic decline in the number of bird species at Assam's Bordoibam-Bilmukh Bird Sanctuary (BBBS). The sanctuary, once home to a rich diversity of avian species, has experienced a 72% decline in bird species over the past 27 years. The study, published in the Journal of Threatened Taxa, highlights the severe biodiversity crisis facing the sanctuary.

Key Findings:

• Bird Species Count Decline:
  • In 1997, the sanctuary recorded 167 bird species.
  • Recent surveys (2022-2024) have only recorded 47 species, marking a 71.85% decline in species count.
• Surveys:
  • 2011 Survey: Recorded 133 species (86 resident, 23 migratory, 24 local migrants).
  • 2017-2018 Survey: Found 120 species, along with a variety of other biodiversity, including macrophytes, fish, and aquatic ferns.
• Impact on Migratory Birds:
  • Migratory species like Brown Shrike, Citrine Wagtail, and White Wagtail (winter migrants), and the Lesser Kestrel (summer migrant) were recorded recently.
• Main Causes of Decline:
  • Anthropogenic Activities: Overfishing, poaching, excessive harvesting of aquatic plants, and egg collection.
  • Land Use Changes: Habitat degradation due to agriculture, machinery noise, and land being used as pasture areas.
  • Disruption of Food Chain: Habitat loss and changes in foraging and breeding grounds for both migratory and resident birds.
• Species of Concern:
  • Poached Birds: Lesser whistling duck, Fulvous whistling duck, White-breasted waterhen, Indian pond heron, Eastern spotted dove, and Yellow-footed green pigeon.
  • Threatened Species: The sanctuary is home to globally threatened species like the Spot-billed Pelican and Lesser Adjutant.

About Bordoibam-Bilmukh Bird Sanctuary:

• Location: Situated between Dhemaji and Lakhimpur districts in Assam, the sanctuary spans 11.25 sq. km at an altitude of 90-95 meters above sea level.
• History: Declared a wildlife sanctuary in 1996, it was originally part of the Subansiri River which has now shifted 7 km from the wetland.
• Climate & Vegetation:
  • Moist tropical climate with an average annual rainfall of around 2,000 mm.
  • The vegetation includes flooded valley grasslands and wetland plants, providing crucial habitat for migratory birds.
• Significance for Avian Species:
  • Hosts a variety of migratory waterfowl, especially during the winter.
  • Home to globally threatened bird species like the Spot-billed Pelican and Lesser Adjutant, along with resident birds such as the Indian Pond Heron and Fulvous Whistling Duck.

Conservation Efforts:

• The decline in bird species at the sanctuary has raised alarm about the degradation of wetland habitats.
  • The study emphasizes that habitat loss can disrupt the food chain, water table, and nutrient cycle, which in turn harms both the ecosystem and human communities.
• The authors of the study advocate for intense conservation efforts to restore and protect the sanctuary’s biodiversity.

Assam's Biodiversity:

• Assam is one of India's most biodiverse states, with around 950 bird species, including 17 endemic species.
• The state also hosts 55 Important Bird and Biodiversity Areas (IBA), which are vital hotspots for avian species.