Study shows decline in Redvented Bulbul ppln

Coimbatore, Apr 1: The population of common bird species, Redvented Bulbul (Pycnonotus Cafer), has declined drastically in the past decade due to the changes in their vegetation at the Point Calimere Wildlife Sanctuary on the Coromandel Coast in Tamil Nadu, according to a study.

A recently concluded a year-long study on 'Monitoring the ecology of the tropical dry evergreen forest in Point Calimere' by the Salim Ali Centre for Ornithology and Natural History (SACON) here revealed that the 'Redvented Bulbul', recorded as one of the most abundant bird species in the earlier study, was now on the verge of extinction.

Similarly, another species, the Red Spurfowl, recorded during the previous study done over ten years ago, could not be sighted by the observers.

SACON scientist P Balasubramanian told UNI, ''the Point Calimere Sanctuary harbours the tropical dry evergreen forest and it is an endangered forest. The tropical forest ecosystems, though biotically most complex are extremely fragile and easily degradable by anthropogenic disturbances.'' The Bombay Natural History Society (BNHS) had done extensive research on various ecological aspects of the sanctuary and created a baseline documents.

''A documentation of avifaunal changes requires a temporal baseline data or information against which subsequent records can be compared and evaluated,'' he said.

The study was done to assess the structure of bird communities in the tropical dry evergreen forest and compare the present status with the past to find out changes if any.

About the methods used for the study, he said they had adopted the methods of earlier BNHS study with five transects, each measuring one km, for bird census and breeding biological studies. The bird censuses were done fortnightly using variable width line transect method.

About the ''possible'' extinction of Redvented Bulbul, Dr Balasubramanian said the plesent study shows that the number of birds has come donw to 10-20 compared to the previous study in which 40 to 50 birds were sighted.

Elaborating on the results of the study, he said, the sanctuary had all the three ecosystems-- forest ecosystem, mangrove forest and lagoon system-- to attract migratory birds from Russia, Europe and Himalayas for a few months every year. Besides, the observers spotted 55 species of birds comprising both residents and migrants. The richness and diversity of bird species was generally high during October-February-- the wet season. It was low during July-September, which is more or less the dry period in Point Calimer.

He said the highest species richness (44) and diversity (2.91) was recorded in February and lowest species richness (25) and diversity (2.06) in September. This also showed that the presence of migratory birds in the wet season contributed to the highest species diversity during this period.

Dr Balasubramanian said during the census they had observed common species like white-Browed Bulbul (Pyononotus luteolus), spottled dove (Streptopelia chinensia), Yellow-bulled Babbler (Turdoides affinis), Common lora (Aegithina tiphia) and Redvented bulbul (Pycnonous cafer).

He said they had also recorded breeding of 11 species of birds-- White-browed Bulbul, Redvented Bulbul, Yellow-billed Babbier, Common Lora, Spotted Dove, Eurasian-collared Dove, Purple-rumped Sunbird, Loten's Sunbird, Common Woodshrike, Brahminy Kite and Pied Cuckoo, he he added.

Most of the bird species were cup-nesters and platform-nesters, preferring shrubs of average 3.6 meter height. Among the 28 nests observed, only 25 per cent were successfully hatched and fledging success was recorded to be only 18 per cent. Egg predation was recorded 68 per cent.

The transects that are found in close proximity to human habitations are affected by human disturbances such as firewood collection, grazing and poaching of eggs by tribal boys, he added.

UNI