In his Mann ki Baat radio programme on Sunday (July 27), Prime Minister Narendra Modi highlighted a “first-ever grassland bird census” in Assam’s Kaziranga National Park and the technology used for this.What is this “bird census”, what was the methodology involved, and what are the concerns surrounding grassland birds?Between March 18 and May 25, a survey to record the grassland bird population in Kaziranga National Park was undertaken by a team of forest officials, scientists, and conservationists.It all began when a doctoral student Chiranjib Bora, who is studying the threatened grassland bird Black-breasted parrotbill, received the INSPIRE fellowship from the central government’s Department of Science & Technology, along with acoustic monitoring tools to conduct his research.He and the Kaziranga authorities then decided to use the tools to count all grassland bird species in the national park, 70% of which is covered by grasslands.“Our main goal was to monitor what grassland bird species live in Kaziranga. Most of the grassland bird species have become rare. These are small and well-camouflaged birds that are not easily spotted, unlike wetland birds. Also, they live in peculiar habitats that are rapidly declining,” said Bora.The survey prioritised 10 species that are either globally threatened or endemic to the Brahmaputra floodplains: Bengal Florican, Swamp Francolin, Finn’s Weaver, Swamp Grass Babbler, Jerdon’s Babbler, Slender-billed Babbler, Black-breasted Parrotbill, Marsh Babbler, Bristled Grassbird, and Indian Grassbird. Including these, it recorded a total of 43 grassland bird species, including 1 Critically Endangered, 2 Endangered, and 6 Vulnerable species, according to the IUCN Red List.What was the methodology and why was it unique?Story continues below this adAccording to Kaziranga National Park Director Dr. Sonali Ghosh, the use of passive acoustic recording monitoring was the highlight of the survey. “Surveying these small, shy, and highly camouflaged birds is very difficult using traditional methods like visual counting. So, the acoustic recorders were placed in tall trees near grasslands during the breeding season of the birds, between March and May. This is the season when they are very vocal, calling out for mates and with males defending territory. The instruments recorded all the birds singing in the landscape,” she said. The survey to record the grassland bird population in Kaziranga National Park was undertaken between March 18 and May 25.Bora said that different tools were then used to identify the birds based on the recordings.“After recording for three consecutive days, we removed the recorders and analysed those sound files. If the sound was not identifiable, we used software to create a spectrogram, which is a graphical representation of the sound, to aid us in identifying. We also used a tool called Birdnet, which uses machine learning to try and identify species by bird song. We covered 29 locations in the national park using six recorders,” he said.What is the significance of the findings?Dr. Ghosh called grassland birds “an indicator of good health” of an ecosystem, likening them to indicators such as BMI for human health. “The presence of these birds tells us that the habitat is healthy,” she said.Story continues below this adThe national park authorities have been particularly excited by the discovery of a breeding colony of the endangered Finn’s Weaver, which is endemic to the Brahmaputra flood plain.“They nest on the tops of trees but till now, we had not known where they had been nesting. During the survey we found a colony of over 85 nests in Kaziranga,” she said.What are the threats to the habitats of grassland birds?Bora said that in the past four decades, Assam has lost around 70% of its grasslands.Story continues below this ad“There are anthropogenic factors such as overgrazing and clearing of grasslands for cultivation. But there is also a natural phenomenon called ecological succession, which is basically an instinct for grasslands to gradually transition to forests. Among the 10 species we had prioritized, three are endemic to the grasslands of the North East, which means that if they vanish from here, they become extinct,” he said.Climate change also contributes to these concerns.“It is a cause of worry. If we look at some species, for instance, the Bengal florican, we used to see a lot more of them, but this time we could detect only one or two. Further study can tell us if the decline is influenced by climate change or other factors,” said Dr. Ghosh.