Bird census: Enumerators use various methods in TN

Counting birds was no mean task as enumerators used various methods such as tracking down their direction and adopting 'call count' strategy to ascertain the population of the winged creatures in Tamil Nadu during the annual census exercise.
The two-day state-wide census, which concluded today, was aimed at presenting the biodiversity of the avifauna as it is and avoid duplication to the maximum extent possible, forest officials said here.
The annual synchronised bird census covered 14 bird sanctuaries and wetlands and was carried out by wild life officials, volunteers, bird watchers, NGOs, ornithologists, and the local people.
"There are several methods to enumerate birds. Whichever is appropriate for a given habitat it is used for carrying out the census," a senior Forest official told PTI.

Explaining he said 'total count' method is followed in an vast expanse of open area where birds are visible.
'Block Count' is used for several flock of birds and it involves splitting an area grid-wise. The number of birds in an individual grid are seen and final estimates are arrived for every block.

'Point Transect' is employed in a wooded region or a forest as in such regions it is not possible to count all the birds. "So stand at a place and count birds which are visible from that point and we know how many areas are scanned and finally such point transect figures will be extrapolated to cover an entire given area"

Line Transect: A person will walk in a line may be for a few kilometres and then count all birds he sees along the line and it will give a density estimate for the given area. Based on that, the population for the extended area is also factored in, the official said.
Call Count: Though it is not easy to spot some birds, they can be identified through their calls and this is followed where birds could not be spotted.
Based on factors including a particular landscape and water bodies also, issues like double count is avoided, he said.
Bird watchers have an excellent knowledge of a whole lot of species and such understanding came in handy to the conduct the survey and avoid duplication at the field level, the official said.

Census results will be announced after computation of inputs from all the centres, he said.