Why are migratory birds giving India a miss?

Why are migratory birds giving India a miss?

Subject :Environment

Section :Species in news

Context:

• Harriers, hawk-like birds, are not visiting the grasslands of India as they were used to in the past. The reason is shrinking grasslands and the grasslands being replaced by trees and agriculture.

Migratory birds:

• Thousands of birds migrate between their breeding and non-breeding grounds twice a year.
• Some migratory birds are the Amur falcon, wandering albatross, Arctic terns, and the bar-tailed godwits(undertake sea-crossings of more than 11,000 km non-stop).
• Reason for their migration:
  • The reduction in day length and temperatures in temperate regions during winter lowers food availability, making the birds move southwards to the warmer tropical regions for food.
  • Another reason is to reduce competition with other related species.

The flyways:

• Long-distance migratory birds have evolved to use certain flight paths for their journeys: called flyways, these span continents and oceans.
• A flyway includes not just migratory pathways but also breeding and wintering ranges.
• Broadly, there are eight migration flyways across the world.
• They were initially classified on the basis of the migration of the waterfowl, which journey in large flocks, but these paths are also used by other birds ranging from small songbirds (passerines) and tiny warblers to large birds of prey (raptors).
• There are three major flyways in Asia:

1. The West Pacific Flyway
2. The East Asian Australasian Flyway
3. The Central Asian Flyway (CAF)

• India falls within the CAF, which is spread across Eurasia from the Arctic Ocean to the Indian Ocean, and geographically spans 30 countries.
• This flyway is used by at least 400 species of birds, which breed in the central Asian region and migrate down south to the Indian subcontinent during winter.
• The topography and ecosystem diversity along the flyway include the high-altitude Himalayan plateau, deserts, lakes and marshes, and steppe/grassland habitats.

Central Asian Flyways (CAF):

• According to the Convention on Migratory Species (CMS), a United Nations initiative, the CAF has the least available information on migratory birds compared with the other major flyways.
• Precise tracking information is available for less than 1 per cent of the bird species using the CAF.
• Threats affect the birds on this route: habitat loss, prevalent practices of hunting, intensive agriculture, and lack of pesticide management.

Bird Count India:

• It is an informal partnership of organisations and groups working together to increase the collective knowledge about bird distribution and population, has been instrumental in promoting small-scale monitoring programmes by individual birdwatchers.

A comprehensive study on birds:

• The State of India’s Birds Report (SoIB), published in 2020, was the first comprehensive study on the distribution range, trends in abundance, and conservation status of most of the bird species that commonly occur in India.
• Based on crowdsourced and citizen science data, uploaded in the eBird platform.
• Analysis of the report:
  • 52 per cent of the 867 species assessed are on the decline. This includes long-distance migratory birds and birds associated with open ecosystems such as grasslands.
  • For example, the species such as pallid harriers, steppe eagles and tawny eagles, all of which migrate to or within India from the central Asian steppes, are getting rarer.

Mapping the migratory patterns:

• Ringing programmes such as EURING have run for decades, mapping the migratory routes of more than 100 species of birds along the Eurasian-African flyways.
• Bird ringing programmes have been going on in India for the last five decades. Although the programme has provided valuable information, the proportion of ring recoveries is very low.
• Some information collected are:
  • Now we know about the high-altitude crossing undertaken by the bar-headed geese across the Himalayas, the long migratory flights of the Amur falcons, the loop migrations across and away from the Himalayas by the demoiselle cranes, the movement and behaviour of threatened species such as the great Indian bustard and the lesser florican, which move within relatively smaller ranges in the arid part of the country.
  • Raptors such as black-eared kites, harriers, and various species of vultures are also being tracked.
• Citizen science bird monitoring initiatives launched in India in the last 10 years include the Common Bird Monitoring Programme of the Bombay Natural History Society, Bird Atlases in a few States conducted by Bird Count India, and the annual Asian water bird census that happens across all major wetlands in India. 
• A study conducted by the Ashoka Trust for Research in Ecology and the Environment (ATREE) documented a decline in 28 per cent of the 50 species observed over 10 years.
  • ATREE has also started species-oriented monitoring initiatives such as the HarrierWatch programme.