The white‐bellied heron in India 733
2008; Fig. 2a). From2007 onwards there have been incidental reports of the heron fromsites east of 40 Mile, up to 65 Mile: in the 52Mile area in 2007 (Umesh Srinivasan and Shashank Dalvi, pers. comm., 2024), at 58 Mile in February 2010 (photographed by RN; eBird, 2021; Fig. 2b), and at 55 Mile and 64 Mile in 2022 (Patgiri et al., 2023; Fig. 2f). Firmbase was previously the preferred location for sighting the heron (Japang Pansa, pers. comm., 2024), but because of improved accessibility following construction of the Miao-Vijaynagar road and fewer sightings in the Firmbase area, bird enthu- siasts now favour 65 Mile as a viewing location (Shashank Dalvi, pers. comm., 2024). Some local people have suggested the species has moved away from Firmbase to the higher reaches of the Noa-Dihing River in the eastern part of the Park, but there are only incidental observations of the heron in eastern Namdapha. We therefore cannot ascertain whether the bird has moved from the central and western reaches to the east or whether the population in central and western Namdapha has declined. Our repeated surveys in Namdapha Tiger Reserve, a sig-
nificant site for heron conservation, demonstrate declines in the white-bellied heron population. Patgiri et al. (2023) also failed to detect the heron around Firmbase, however, they reported a sighting at the confluence of Namdapha and Noa-Dihing. We do not know the reasons for the declines in the western and central parts of Namdapha; previous studies have suggested anthropogenic disturbances as a pos- sible driver (Stanley Price & Goodman, 2015; Patgiri et al., 2023), but we noted a reduction in human activities in the protected area between our 2017 and 2023–2024 surveys. When comparing the number of 100 m river segments within a site with signs of fishing, we found evidence of fishing in 5.6% of segments in 2017 (Menzies et al., 2021) but in only 1.8% of segments during 2023–2024, despite nearly four times the survey effort. Similarly, we recorded human presence in 9.5% of segments in 2017 (Menzies et al., 2021) and 7.6% during 2023–2024. The surveyed riverine habitat inside the protected area has remained mostly un- altered, and human activity (except by villagers staying around Firmbase) along the river has probably declined following the recent road connectivity between Miao and Vijaynagar that enables direct transportation between the various settlements, reducing the need for people to walk and camp along the river. Annual rainfall in the Changlang District is 3,800–4,866 mm (Government of Arunachal Pradesh, 2024) and there have been no adverse weather events that could have significantly impacted the rivers in recent years (Japang Pansa, pers. comm., 2024). In February 2023, we observed a school of dead fish at Firmbase, probably killed by dynamiting, but in our surveys during November 2023–March 2024 we did not detect any evidence of destructive fishing methods inside Namdapha Tiger Reserve, although fishing continues inside the Reserve. Knowledge of temporal changes in fish abundance, a
potentially important driver of white-bellied heron abun- dance, is poor; the abundance of fish species known to be eaten by the white-bellied heron (Khandu et al., 2021; Mondal &Maheswaran, 2021) needs to be compared between the eastern and western parts of the Reserve. Our findings suggest there has been a decline in the num-
ber of white-bellied herons in central and western Namdapha, either because of local extirpations or themove- ment 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. As part of the river bird study during November 2023–March 2024,we also surveyed areas outside Namdapha and Kamlang Tiger Reserves (Menzies et al., unpubl. data), butwe did not detect the spec- ies. 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 (Reddy et al., 2021), are critical to determine nesting sites in the region as this species appears to be on the verge of extinction. An improved understanding of the reasons for the species’ decline would benefit the conservation manage- ment of the eastern population.
Author contributions Study design: all authors; fieldwork: RKM, RN; writing: all authors.
Acknowledgements We thank Japang Pansa, Dhan Bahadur Limbu, Laiphung Wangnow and Phupla Singpho for assisting with fieldwork; Vidyadhar Atkore for useful discussions; the Arunachal Pradesh Forest Department for providing necessary research per- mits (CWL/GEN/2018-2019/Pt.IX/NG/352-57); and The Rufford Foundation (project 37739-1) and Rohini Nilekani Philanthropies for funding this project.
Conflicts of interest None.
Ethical standards This research abided by the Oryx guidelines on ethical standards.
Data availability All data generated during the study are presented in the paper. The locations of white-bellied heron records can be requested from the corresponding author.
References
ACHARJA, I.P. (2020) Evaluation of nest habitat, site preferences and architecture of the critically endangered White-bellied Heron Ardea insignis in Bhutan. Bird Conservation International, 30, 599–617.
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insignis.In The IUCN Red List of Threatened Species 2018.
dx.doi.org/10.2305/IUCN.UK.2018- 2.RLTS.T22697021A134201407.en.
EBIRD (2021) An Online Database of Bird Distribution and Abundance. Cornell Lab of Ornithology, Ithaca, New York, USA.
ebird.org [accessed April 2024].
Oryx, 2024, 58(6), 730–734 © The Author(s), 2025. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605324001583
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