Guwahati: Deep within the riverine forests of Arunachal Pradesh, one of the world’s rarest birds—the white-bellied heron—is slipping away almost unnoticed. Once a symbol of resilience in Namdapha Tiger Reserve, this Critically Endangered heron now teeters on the brink of local extinction. Two recent studies—one mapping its alarming disappearance from known strongholds, the other decoding its nesting secrets—paint a sobering picture of a species in peril.
Globally, fewer than 60 white-bellied herons are thought to survive. These large, solitary, fish-eating birds have a fragmented distribution across Bhutan, Myanmar, and northeast India. Namdapha, spanning nearly 2,000 square kilometers, has long been a bastion for India’s eastern population. But now, even here, the silence is growing louder.
In 2017, field surveys led by Rohan K. Menzies recorded a promising encounter rate of 0.55 individuals per kilometer of river surveyed—seven herons in all. Fast forward to 2023–2024, and those same riverbanks yielded none. Despite intensified survey efforts across 45 kilometers, no individuals were detected during transect walks. Only three herons were seen incidentally outside survey transects, suggesting either a dramatic population decline or a shift to new, unknown habitats.
But this isn’t the first time the heron has hinted at deeper troubles. In a complementary long-term study between 2013 and 2017, researchers Himadri Sekhar Mondal and Gopinathan Maheswaran documented two nesting attempts in Namdapha. These were only the second and third confirmed nests ever found in India. Both were painstakingly observed—one in 2014, the other in 2015. Both failed.
Their study revealed vital insights into the species’ nesting behavior. Unlike their Bhutanese counterparts that nest in Chir Pine forests, the Namdapha white-bellied heron chose broad-leaved forest edges near the Noa-Dihing River. They built large nests high in tall trees—up to 25 meters above the ground—preferably on the forest’s northern edge, facing east to catch the early sun. Nesting was most intense in the cool morning hours, with birds making over 90% of their nest material trips between 6:30 and 8:30 am.
Despite these adaptive strategies, no chicks ever fledged. In 2015, the nest collapsed. A broken eggshell was found near the site. The reasons remain unclear, but possible culprits include predation, poor nest structure, or environmental stress.
The convergence of findings from these two studies is both crucial and haunting. On one hand, they demonstrate how little we still know about the heron’s movements, breeding patterns, and survival challenges. On the other hand, they show that the central and western stretches of Namdapha—once the bird’s strongholds—may now be empty.
Interestingly, human disturbances, often the usual suspects in wildlife declines, appear to have decreased in recent years. Fishing activity and human presence along river segments have dropped, likely due to improved road connectivity reducing foot traffic. The physical habitat has remained largely intact, and no extreme weather events have been recorded in the region.
The study led by Rohan K. Menzies suggests there has been a decline in the number of white-bellied herons in central and western Namdapha, either because of local extirpations or the movement of birds to other areas (e.g. further east). “There is a need for systematic surveys of the white-bellied heron in the eastern part of Namdapha. Moreover, systematic efforts to locate and monitor heron nests away from the core area of the Reserve are crucial to determine breeding success and potential influencing factors,” the study says.
As part of the river bird study conducted during November 2023–March 2024, the team also surveyed areas outside Namdapha and Kamlang Tiger Reserves but did not detect the white-bellied heron. “Systematic surveys and long-term monitoring in more remote parts of Kamlang and the higher reaches of Anjaw District, in addition to monitoring the known individuals, are critical to determine nesting sites in the region as white-bellied heron appears to be on the verge of extinction. An improved understanding of the reasons for the species’ decline would benefit the conservation management of the eastern population,” the study emphasizes.
Also Read: EastMojo Exclusive: RTI shows major gaps in Mizoram refugee data
You just read a story that took days to report. Help us keep our reporters on the ground in the Northeast.
Ad-free reading, support and keep important stories alive
Support once (any amount)
Scan to pay via UPI