A threat to the survival of White-Bellied Herons in Bhutan
While Bhutan plays a pioneering role to protect the critically endangered White-bellied heron, an endangered bird species across the world, with the establishment of the Punatshangchhu hydro project, ornithologists from Royal Society for Protection of Nature (RSPN) say the habitat of this species has been affected.
RSPN’s ornithologist Rebecca Pradhan said birds have started to vanish from the place where they were spotted before, and the ever growing population along the Punatshangchhu each year has led to disturbance of the birds’ habitat.
The total number birds have now dropped to around 22.
Attacks on birds and their eggs by predators is a major threat as well. The pressure on the birds has further risen with the lack of scientific approach and lack of awareness among the local communities. Heron habitat could also be defragmented with pro-developmental activities such as, hydropower generation and road creation.
Forest fire was another factor affecting the habitat of the birds, though not on a major scale.
Rebecca Pradhan said back In April 2013, the nest in Bertichu was found destroyed and one of the birds was found dead. Though the cause of the death is not yet confirmed, but she said the bird might have been killed due to a landslide or due to natural predation.
Though hydropower construction may not be the single cause for the decline in the White-bellied heron population, but it can partly be attributed to such development, as the bird is highly vulnerable to disturbance (tolerance distance to human disturbance is estimated to 200 metres). The Punatsangchhu basin is the largest habitat for the White-bellied heron in Bhutan, and therefore, the survival of this bird will depend on how safe the basin is for them to feed, roost and breed.
While in the second nest at Burichu, the chicks could not be hatched till the end of June 2013. The reports in the past have indicated that the chicks normally hatched in April and by July they fledge out of nest. The reasons for the unsuccessful hatching were not known.
The other reason affecting the habitat of the birds is the disturbances caused by bird watchers, mostly by conservationist and visitors who kept visiting the area on regular basis to take photographs and monitor the nesting site.
The White-bellied herons were first spotted in 2003 along the Punatshangchu basin after which RSPN started monitoring them, although Rebecca Pradhan had personally started the monitoring of the birds back in 1991.
With just about 20 to 22 birds remaining of this species in their natural habitat, RSPN has initiated study on its ecology and breeding behavior, the rapid pace of development activities calls for immediate interventions that could provide quicker options for the survival of the bird species.
Measures are being taken by RSPN to save the birds, such as captive breeding funded by Punatshang chhu project 1 to increase the population of the birds.
“If there is no disturbance in their habitat then the chances of their survival and increase in the population can be increased,” Rebecca Pradhan said.
With roughly 200 White-bellied herons (Ardea Insignis) in the world today, herons are among the 50 rarest bird species on earth. Herons mostly dwell in Southeast Asian countries, and presumably Bhutan shelters a little over 30 herons in the nation.
In Bhutan, eight nesting sites have been identified amongst lofty flowing waters with pebbly substrates and Chirpine forests. Another characteristic feature of the White-bellied herons is their unique courtship system which begins in the winter from January to February as the river water recedes.
Chencho Dema/ Thimphu