SINGAPORE - Singapore's first heron count in a decade has turned up fewer of the big birds than before. The numbers of four common species - grey herons, purple herons, black-crowned night herons, and striated herons - have dwindled by as much as three-quarters, and no herons at all were seen at 19 of the 57 survey sites.
The data from the National Parks Board's Heron Watch came from 185 volunteers who fanned out across the island on Aug 31. The findings were presented yesterday at Sungei Buloh Wetland Reserve's 20th anniversary celebrations.
Herons - said to be easy for new birders to spot - feed on fish, hence they are good indicators of wetland health.
The latest numbers are probably not as bad as they look though, said ornithologist and nature educator Wang Luan Keng.
The volunteer coordinator of the survey said it was high tide on the morning of Aug 31, so herons' regular feeding grounds like monsoon drains and mudflats were underwater.
But Ms Wang noted the sharp decline in sightings of the black-crowned night herons - 51 this year from 194 in 2003 - "is probably real", due to the loss of nesting sites when some trees were trimmed around Jurong Bird Park where they nest.
The sensitive birds will abandon their nests if disturbed, she said. At sites where no herons were spotted, like Sembawang Park and the zoo, construction or other activity might have scared them off.
And while herons still thrive at the pristine wetlands of Tampines, Lorong Halus and Pulau Ubin, they are disturbed by kayakers on Sungei Tampines and photographers creeping along the river bank to shoot the nesting birds, added Ms Wang.
"The herons may seem resilient but they are highly sensitive during breeding," she said.
"The causes are mostly man-made - direct human disturbance from water activities, fogging and habitat destruction.
"If we do not take more measures to actively protect these birds and their breeding colonies, we risk losing these iconic birds of the wetlands."