In what may be a drawback for the conservation of the endangered white-bellied heron, there has been no hatching reported this year.
According to a report by Jigme Dorji, a heron researcher and a member of the IUCN-SSC Heron Specialist Group, of the two nests along two major river basins in the country, both didn’t see a hatching this year.
One nest was found in Bertichu, a tributary of Mangdechu basin in Zhemgang and the other in Burichu, a tributary of Punatsangchu basin.
Although the actual cause could not be determined it has been attributed to natural predation and human disturbances.
“With less human disturbances seen near the first nest, the destruction of the nest could probably be attributed to natural predation,” says the report.
According to the report, there were cases in the past where chicks of white-bellied heron fell prey to predators like the Serpent Eagle, Pallas Fish Eagle, Osprey, Yellow Throated Martin and to some small cats.
However, at the second nest the chicks could not be hatched despite the breeding pairs sitting on the nest till the end of July.
Jigme Dorji reports that since the nest was near to the Wangdue-Tsirang Highway, the disturbance by vehicular noise might have caused stress to the bird sitting on the nest leading to inconsistency in temperature for incubation of the egg.
“The other reason might be disturbance by humans mostly by conservationist and visitors who kept visiting the area on a regular basis to take photographs and monitor the nesting sites,” says Jigme Dorji.
According to the report, the causes might vary in opinions of different people but the immediate concern would be to see why such natural process failed after ten years of its successful breeding in Bhutan.
The report also indicates that the population of the white-bellied heron has declined over the past years.
The report shows that the population of the bird in Bhutan could be anywhere between 12 to 24 individuals. Although the Royal Society of Protection of Nature (RSPN) has recorded 30 individuals in 2009 the report says that this was before the construction phase of the Punatsangchu hydropower project.
“The hydropower construction may not be the single cause for the population decline but can be partly attributed to them, as the bird is highly vulnerable to disturbances,” says the report.
The first nest of the white-bellied heron was discovered at Zawa, a remote village in Wangduephodrang in 2003. Since then RSPN has been involved in the conservation of the endangered bird.