Is the population of the Critically Endangered white-bellied heron declining in Namdapha Tiger Reserve, India?

Abstract The Critically Endangered white-bellied heron Ardea insignis is a large-bodied, range-restricted, piscivorous bird of the Himalayan mountains. With fewer than 60 individuals remaining globally, regular monitoring is required for this rare species. We present the results of surveys during 2017 and 2023–2024 in Namdapha Tiger Reserve, Arunachal Pradesh, India. The encounter rate of white-bellied herons in 2017 was 0.55 individuals per km of river, but we did not detect the bird during intensive surveys in the same location during 2023–2024. The surveyed area within the Reserve was once a stronghold for the species, but its population appears to be declining. Monitoring the population has helped reveal this decline, but identifying and conserving stretches of river still utilized by the remaining individuals is now critical.