Bhutan recorded 25 critically endangered white-bellied herons (WBH) this year, an increase by one, indicating that the country is rich in biodiversity and its habitat intact.
A nationwide WBH population survey, 2019 conducted from March 2-6 found 16 individuals in Punatsangchhu basin, six in Mangdechhu and its tributaries, one in Kurichhu, and two in Phibsoo Wildlife Sanctuary.
“The presence of the species in such number is an indication that our biodiversity is rich and the habitat intact,” senior ecologist at the Royal Society for Protection of Nature (RSPN), Rebecca Pradhan said. “However, the species is globally rare by nature.”
According to the survey, the river systems harboring major WBH population are Kishona Chhu in Punatsangchhu basin and Tshaidang Chhu, a tributary of the Mangdechu which harbored four individuals each.
Rebecca Pradhan said the survey found that Kishona chhu had relatively shallow water with availability of feeding habitats. There are fewer disturbance factors such as an absence of transmission lines, roads and infrastructure facilities and human settlements concentrated along the tributary.
Bhutan today has 41.6 percent of WBH global population, which is estimated at 60.
The WBH population was expected to increase to 29 in addition to the 24 adults recorded last year. Five juveniles were recorded this year.
“However, we could count only 25 this year excluding a casualty found in Pangna, Dagana,” one of the researchers with RSPN, Tshewang Lhendup said. The cause for its death is unknown and he said that the Department of Forests and Park Services and RSPN are still investigating.
That the survey counted only 25 individuals could be due to technical lapses that may have occurred during the survey or there may have been more casualties. Of the six breeding pairs that were observed trying to build the nests, three did not succeed. Rebecca Pradhan said that since they are juvenile pairs, they could have lacked skills in nest building.
During the survey, three active nests were observed on the broad leaf trees at Kishonachhu and Wakleytar along Punatsanchhu basin, and at Tshaidang. In earlier studies, the species was known to breed and roost in Chirpine forests.
Rapid pace of developmental activities along the rivers, extensive habitat fragmentation due to degradation and disturbance of forests and wetlands, wildfire intensity, unsustainable fishing activities, water pollution, predation and growing tourism activities like rafting and kayaking are posing the greatest threat to the conservation of WBH in the country today.
In response to the challenges and threats to the survival of the endangered WBH, a bird’s captive breeding center is under construction in Changchey area, Tsirang. RSPN is constructing the center with financial support from Punatsangchhu Hydropower Project Authority and the government.
According to Rebecca Pradhan, this ambitious project was taken up after RSPN attempted captive breeding and successfully hatched a chick earlier.
The captive breeding center will be equipped with an incubator, laboratory, aviaries and feeding habitat to rear chicks. The project is expected to complete by the end of this year and will try to operate by the beginning of 2020.
The primary objective of installing captive breeding is to establish an insurance population against the extinction of the species once the individuals are reintroduced into the wild. It is also aimed to understand key information about the behavior and biology of the bird since little is known today.
One of the key actions planned is to tag young herons with satellite tracking devices before reintroducing into the wild to better understand their dispersal and threats.
Bhutan, Rebecca Pradhan said, is the first country in the world to establish captive breeding of the WBH. “Currently, we lead both in confirmed numbers as well as in efforts towards its conservation and protection and, we must work towards improving the conservation status of WBH.”
The survey engaged 21 Forest Resource Group (FRG), 11 Local Conservation Support Group (LCSG) and 10 staff RSPN in 30 known and potential habitats within eight dzongkhags.
The white-bellied heron Ardea insignis (Hume) is at significant risk of extinction across its entire home range. Recognising the overestimation of 200-250 individuals than its actual confirmed number, 60, and owing to its fast declining trend, WBH’s status was consigned to ‘Critically Endangered’ on the IUCN’s Red List for Threatened Species, 2007.
Global WBH distribution is restricted to the Eastern Himalayan foothills. As of 2014, its occurrence was reported from only three countries with Bhutan leading in the confirmed numbers, followed by Myanmar and India.