New study provides insight into Vengurla archipelago ecosystem | Bombay News
Mumbai An ongoing study by the Salim Ali Center for Ornithology and Natural History (SACON) – funded by the Mangrove Foundation of the state forestry department – has given researchers key information about the biodiversity of the archipelago of Vengurla in the Sindhudurg district, known to be home to the largest congregation of Indian swifts, a protected bird species endemic to the Western Ghats of India and Sri Lanka.
In particular, the researchers observed that these salangans and other birds are essential for the survival of various troglodyte invertebrates in the region, as their droppings provide energy in the absence of light and vegetation.
The Vengurla Archipelago consists of about 20 islets, about 10 km from the coast, of which three islets are relatively large, namely New Lighthouse Island, Old Lighthouse Island and Burnt Island. The birds are found in the four caves between the new lighthouse and Burnt Island. One of these caves, called Pakoli Ghal on Burnt Island, is where Indian Swanganas nest and roost by the thousands.
Other species including rock pigeons, tawny pipits, dusky swallows, and western reef egrets have also been seen here. In 2012, the Bombay Natural History Society (BNHS) designated these rocks as an Important Bird Area (IBA), making it one of 467 such sites across the country.
The salangana is particularly vulnerable because its nests (made up of hardened saliva) are used to cook a Chinese specialty called bird’s nest soup. Vengurla has already witnessed widespread poaching of swangas nests (before the species came under wildlife protection law) and between 2001-02, seven smugglers operating in the area were arrested.
“Fortunately, during our study period, we found no indication that this activity was continuing,” said Dr Shirish Manchi of SACON, who is leading the study and has spent two decades working on the conservation of the Edible Nest-Swiftlet (a species) in the Andaman and Nicobar Islands.
In an interim report submitted to the Mangrove Foundation in March this year, and which was shared with the Hindustan Times this week, the researchers noted that “a detailed study of the flora and fauna of these islands has not been carried out … Most of the visits of researchers or naturalists to the rocks of Vengurla were intended to explore the avifauna on the islands and in the caves. SACON attempted to document, for the first time, the different orders of troglodyte fauna and their relationship with these birds.
“We conducted three repetitive and systematic surveys during the pre-monsoon season (December to February) at Pakoli Ghal on Burnt Island. We have documented the presence of invertebrates of eleven different orders; (1) Diptera (flies, mosquitoes), (2) Orthoptera (crickets), (3) Lepidoptera (moths and butterflies), (4) Araneae (spider), (5) Crustaceans (Crabs), (6) Blattodea (Cockroach ), (7) Coleoptera (Scarab), (8) Hymenoptera (ants), (9) Microlepidoptera (Micro-moths), (10) Squamata (Gecko) and (11) Scolopendromorpha (Centipedes) ”, they wrote, adding that work is underway to identify these taxa at the species level.
“Since March 2021, in the post-monsoon season, we may have encountered even more invertebrate orders, which will be detailed in a final report early next year. Since the caves are very remote and don’t have much light, the survival of these invertebrates depends on the birds, which defecate in the caves and provide an important source of energy, ”explained Manchi. Guano contains large amounts of nutrients like nitrate and ammonium, and over time accumulates to form a substrate on the rocky surfaces of the cave.
For example, during the study, researchers observed that plaster bagworms and beetle larvae fed and lived in the droppings of swangas. “The Indian Swifts inside the cave play a vital role in providing shelter and an unlimited food supply to various organisms in the caves. Therefore, the presence of a diversity of species orders is apparent, ”the researchers noted.
Rock pigeons, they found, also brought vegetative nest building materials, which fall to the cave floor and are then used as a source of energy by invertebrates. “Further studies will be needed to understand the contribution of each bird to the cave ecosystem,” the interim report said.
These findings are important because biospeleology (that is, a branch of biology dealing with the study of “troglofauna”, or organisms living in caves) is at a very early stage in India. “With the exception of a few caves in the states of Meghalaya, Chhattisgarh, Andhra Pradesh and the Andaman Islands, we do not have systematic studies of cave fauna in the country despite their significant potential,” he said. added Manchi.
This study will also form the basis of a larger SACON project – funded by the Union Environment Department – investigating the biology, ecology and conversational value of Indian Swifts in Maharashtra. Commissioned in January 2020, this study has been delayed due to the pandemic. “We also hope to write a comprehensive document on the fauna of the Konkan caves, from Palghar in the north to Sindhudurg in the south, which has never been done before. But this will have to be done as a separate exercise, ”added Manchi.
Dr Manas Manjrekar, deputy director (research) at the Mangrove Foundation, explained that the forestry department may also consider launching ecotourism activities in the region. “But before we can make a decision on this, we need to have a basic understanding of how the ecosystem works. The tourist part is now secondary, ”he said.
Bhau Katdare, founder of the NGO Sahyadri Nisarga Mitra, which for the first time detected poaching from the nests of salanganas in Vengurla twenty years ago, declared: “We knew that these islands were used as a zone of breeding and nesting for a number of coastal birds, including swangas. . There is even a mention in the Maharashtra State Gazzeteer of the official sale of these nests. When we first visited the island in 2000, we saw that there were long bamboo ladders and scaffolding that had been set up specifically for the purpose of securing the nests in the high areas of the caves, but thanks to the efforts of ours and the forestry department, this is not possible. no longer a practice there and we saw the population of swangas double. But when it comes to the caves themselves, very little is known about them.