Tillangchong, Camorta, Katchal, Nancowry and Trinkat

Site description (2004 baseline):

Site location and context
The Nicobar Islands can be divided into three distinct subgroups: the Great Nicobar subgroup, the Nancowry subgroup and the Car Nicobar subgroup. Tillanchong, Camorta, Katchal, Nancowry and Trinkat Islands lie in the Nancowry subgroup of islands, c. 58 km north of the Great Nicobar subgroup. This subgroup consists of 10 islands and smaller islets of which one island and two islets are uninhabited (Sankaran 1998). Of these, three islands are larger than 100 sq. km, two are 36 and 67 sq. km and three are less than 17 sq. km. Tillanchong is uninhabited and a wildlife Sanctuary (Sankaran 1995). The climate of these islands can be defined as humid, tropical coastal. The islands receive rainfall from both the southwest and northeast monsoon, with maximum precipitation between May and December, and the driest period between January and April (Sankaran 1995). The forest type of the Nicobar Islands can be broadly classified as Andaman Tropical Evergreen, Andaman Semi-Evergreen, Littoral Forest and Tidal Swamp Forest (Mangrove), the inland areas being either forested or grasslands, and a significant proportion of the coast being mangroves.

Key biodiversity

AVIFAUNA: A total of 128 of birds are known from the Nicobar group of islands (Abdulali 1964, 1967; Das 1971). During his study on the Nicobar Scrubfowl (=Megapode) Megapodius nicobariensis, Sankaran (1998) recorded 57 bird species. Later, Sivakumar and Sankaran (2002) added four more species (Lesser Frigatebird Fregata ariel, Large Hawk Cuckoo Hierococcyx sparverioides, Ashy Drongo Dicrurus leucophaeus, and Eyebrowed Thrush Turdus obscurus) to the checklist. None of them are presently of much conservation concern, but worth monitoring. Perhaps the most important bird is the Nicobar Megapode Megapodius nicobariensis nicobariensis, a subspecies of the Nicobar megapode occuring on seven islands of the Nancowry group: Camorta, Nancowry, Trinkat, Katchall, Teressa, Bompoka, and Tillangchong. The population of this subspecies is between 600 to 2100 breeding pairs (Sankaran 1998), while the other subspecies abbotti is much more common. The Nicobar Bulbul Hypsipetes nicobariensis is exclusive to the Nancowry subgroup. It is facing a threat from the introduced Andaman Red-whiskered Bulbul Pycnonotus jacosus whistleri, which is endemic to Andaman Islands, as both species probably occupy the same ecological niche (Sankaran 1998). The British introduced the Andaman Red-whiskered Bulbul to Comorto in the late 1800s. It is now also present on Nancowry, Trinkat, Katchall, Teresa and Car Nicobar (another IBA). The Nicobar Sparrowhawk Accipiter butleri is endemic to the Nicobar Islands. Ali and Ripley (1987) have recognized two subspecies from Nicobar islands: Katchal Shikra Accipiter badius obsoletus and Car Nicobar Shikra A. badius butleri, while Inskipp et al. (1996) and Grimmett et al. (1998) have recognized only Nicobar Sparrowhawk Accipiter butleri as valid species. Recently, Rasmussen and Anderton (in press) have also considered Accipiter butleri as full species. Sankaran (1998) considers butleri to be endangered. BirdLife International (2001) has listed it as Vulnerable and Restricted Range (Endemic) because it is confined to ‘Nicobar Islands Endemic Bird Area’. The primary threat to this species appears to be habitat loss. There are nine Restricted Range species in the Nicobar Islands (Stattersfield et al. 1998). Except for the Nicobar Parakeet Psittacula caniceps, which has been reported from the islands of Montschall, Kondul and the Great Nicobars (Abdulali 1964), all other species have been reported from this IBA. Sankaran (1998) has listed 37 bird species from these islands. Recently, Rasmussen and Anderton (in press) have upgraded many subspecies to full species. The ‘new’ species occurring in these islands are the Andaman Pompadour Pigeon Treron chloroptera, earlier considered as a subspecies of Treron pompadora. It is still a common bird and Sankaran (1998) found it on all the five islands that constitute this IBA. Similarly, the Nicobar Green Imperial Pigeon Ducula nicobarica, an earlier subspecies of the widely distributed Green Imperial Pigeon Ducula aenea (Ali and Ripley 1987, Grimmett et al. 1998) was also found in all the islands of this site. Both species are not immediately threatened but they have to be considered as Restricted Range species because total habitat available to them is much below 50,000 sq. km (the EBA criteria, see Stattersfield et al. 1998). The Nicobar or Hume’s Brown Hawk-owl Ninox scutulata obscura has become Ninox obscura. It could be a very rare species as Abdulali (1967) did not record it in the Nicobars, and Sankaran (1998) also did not see it in any of the five islands. It could be one of the rarest endemic birds of the Nicobar Islands. More information is required to determine its status.

OTHER KEY FAUNA: The only large terrestrial native mammal is the Andaman Wild Pig Sus scrofa andamanensis. Some people claim that even this was brought in by earlier settlers from wherever they came. Other fauna includes the Nicobar Short-nosed Fruit Bat Cynopterus sphinx scherzeri, and the endemic Nicobar Flying Fox Pteropus faunulus. The unique herpetofaunal diversity of this region includes Cantor’s Pit Viper Cryptelytrops (Trimeresurus) cantori, an endemic and rare species of reptile, which is reported only from two localities Camorta Island and Car Nicobar, and is considered as Vulnerable by IUCN. Another endemic and endangered species, Nicobarese Worm Lizard Dibamus nicobaricum is also reported from this area (Anon. 2001).

Pressure/threats to key biodiversity
MAIN THREATS: Construction and impact of free port; Immigration of mainlanders; Plantations; Infrastructure; Disturbance to birds; Hunting and predation; Urbanisation/ industrialisation.

Based on the number of endemics present, the Nancowry group of islands was identified as an IBA of prime importance to avifauna. Katchall, Camorta and Nancowry were identified as priority areas for avian conservation. Several developmental plans are proposed for the Nicobar Islands, particularly the building of a dry dock and refuelling base for international shipping in the Galathea Bay, and making Great Nicobar a free port. If implemented, these will irrevocably damage the island ecosystem and cause immediate loss in the biodiversity of the islands as they are much too small to sustain the impact of such activities. Alteration of the ecosystem would adversely affect and accelerate the extinction of endemic avifauna including the Nicobar Megapode. This species is also under severe pressure due to hunting and predation of eggs by the Monitor Lizard. But the primary threat to the Nicobar Megapode is habitat loss due to the increasing human population, this being most acute in the Nancowry group of islands. Over 600 ha of primary forest were replaced with rubber plantations on Katchall. Expanding townships, development of new roads, airstrips and infrastructure for defence establishments, are all compounding the problem (Sankaran 1995).

Key contributors: Ravi Sankaran and K. Sivakumar.

Recommended citation
BirdLife International (2023) Important Bird Area factsheet: Tillangchong, Camorta, Katchal, Nancowry and Trinkat. Downloaded from on 28/11/2023.