The majestic White-Bellied Heron is slowly disappearing from the face of the earth. However, Bhutan’s story gives some hope to save this magnificent bird
By Sonam Choki
A recent White-bellied Heron (WBH) annual population survey conducted in the country by the Royal Society for Protection of Nature (RSPN) counted 22 herons in the country.
The survey confirmed 19 adults and three sub-adult individuals, which is five less than the previous year.
It was detected that the decrease in population was mainly observed in upper Punatsangchhu basin; Phochu, Mochhu, Adha and Harachhu which were oldest and previously the most abundantly used habitats in Bhutan.
The survey covered all currently known and expected habitats along Punatsangchhu, Mangdechhu, Chamkharchhu, Drangmechhu, Kurichhu, Kholongchhu and major tributaries.
For the survey, RSPN officials divided habitats across the country into 53 priority zones and surveyors were deployed to look for the WBH from 7:00 AM to 5:00 PM for five consecutive days within their designated zone.
A total of 82 surveyors from the RSPN, Department of Forests and Park Services (DoFPS) and Local Conservation Support Groups (LCSG) were engaged in the survey, and for every White-bellied Heron sighted during the survey, observer, date, time, GPS location, count, age, and activity were recorded.
In addition, all bird species sighted during the survey were also enumerated for record and to study the diversity and population trend of associated species within the area.
The study conducted by RSPN revealed a total of 117 bird species; 59 waterbirds and 58 other species were recorded during the survey. The survey was conducted using Epicollect5 digital data collection platform.
Further, three live nests were also located during the survey of which two had three eggs each and one pair was found building a nest.
RSPN states ‘the extremely low and shrinking population of the WBH globally is attributed to human exploitation, disturbances, and loss of riverine habitat. And Bhutan is no exception.’
In Bhutan the bird is threatened by three major challenges across the region one key reason being habitats being lost to infrastructure development, agriculture expansion, hydropower projects, extractive industries, and climate change.
Other attributes are that most of the few remaining habitats are increasingly under pressure due to incautious eco-tourism and recreation, diminishing food resources, pollution, fragmentation, forest fires, and both man-made and natural calamities.
Finally, the small population is under crises with increased mortality and declining breeding success.
Therefore, the RSPN states, it is easily foreseeable that such human-made and natural disturbances would lead to the extinction of this highly vulnerable bird if timely conservation interventions are not taken.
“Concerning the risk, RSPN, in collaboration with relevant agencies and stakeholders, has been working on recovery of population size through research and surveys of population, nests, feeding habitat, distribution, movement, habitat needs, and associated threats,” RSPN states.
Furthermore, since the inception of WBH conservation projects at RSPN, the annual population survey has been an annual event and it helps RSPN understand the trend, priority habitats and it is a basis for needful further conservation interventions.
During the survey, 280 kilometers stretch of Punatsangchhu, 160 kilometers of Mangdechhu, 45 kilometers of Chamkharchhu, 200 kilometers of Drangmechhu, 95 kilometers of Kurichhu and 65 kilometers of Kholongchhu and their tributaries were surveyed by 82 surveyors.
Based on the records, 19 were confirmed as adults, and three sub-adults. Of the 10 sites, where herons were recorded this year, 6 falls under Punatsangchhu basin, and four under Mangdechhu basin.
RSPN stated that for the first time, an individual was recorded from Chamkharchhu basin. Although its presence is Chamkharchhu was known before, only this year, it has been observed during the annual survey.
Similarly, 64% (14 individuals) of the birds were found in the Punatsangchhu basin, and 46% (8 birds) in Mangdechhu basin. Overall, there is decrease in population by five individuals from the previous year.
RSPN noted that the change is population was mainly observed in the upper Punatsangchhu basin; Phochu, Mochhu, Adha and Harachhu which were oldest and previously the most abundantly used habitats in Bhutan.
“Unfortunately, for the first time in 19 years, no heron was sighted in Phochhu and Mochhu which once host highest and oldest known population in the country. No birds were also sighted in Kurigongri basin and lower Mangdichhu basin,” the findings reveal.
In addition, RSPM reveals there is a noticeable change in local population demographics in key foraging habitats over the years. The population in older habitats; Phochu, Mochhu, Punakha, Zawa, Kamechhu, Adha, and Nangzhina has drastically declined over the surveyed years.
It also observed that the Phochhu and Mochhu areas had eight birds during 2007 and 2008, but none were observed this survey. Similarly, no birds were seen after 2013 in Zawa and the Harachhu area, the oldest nesting site, where 6–8 birds were found before 2008.
“Overall, population trends are decreasing in Adha, Nangzhina, and proximate areas, which were historically preferred feeding and nesting habitats until 2010. The population in Berti was highest in 2009,” RSPN’s study revealed.
While no birds were seen during the 2010 census, RSPN observed that the population in lower basin of Mangdechhu is improving today, particularly in Goling and Tsaidang.
However, in contrast to these declining areas, in recent years, more individuals have been sighted in lower regions of Punatsangchhu and Mangdechhu basins, which are also newly discovered sites.
Mithuntar, Dagachhu catchment, Balwani, in lower basin of Punatsangchhu and Tsaidang in lower basin Mangdechhu are the most promising sites with both population trends and nesting sites in sharp increase today.
About the magnificent bird
The White-bellied Heron is categorized as critically endangered under the IUCN Red List of threatened species and protected under the Schedule I of Forests and Nature Conservation Act 1995 of Bhutan.
It was listed as threatened in 1988, uplisted to endangered in 1994, and to critically endangered since 2007.
The distribution of WBH to undisturbed freshwater river systems and its piscivorous feeding behaviour can be easily associated with the health of the ecosystem and pristinely environment.
They are the indicators of our freshwater river systems. Their presence in our rivers indicates the health of the rivers, the fish population, water quality, the health of associated freshwater biodiversity, level of disturbances, pollution, and above all, intactness of our nature.
They are predator, they are prey and they are player in a food chain. They are our natural wealth, our pride, and our heritage. By protecting them and their habitats, we protect our rivers, waters, landscapes, biodiversity, food, and the livelihoods of the local communities.
The first WBH population survey was conducted in 2003, and it has been an annual event since then. Today, the conservation of WBH is not only a flagship program but it is at the forefront of RSPN’s core mandate.