The Bombay Natural History Society, a pan-India wildlife research organization, has suggested a series of conservation measures for the safe and undisturbed winter sojourn of avian guests to Chilika, Asia’s largest brackish water lake and the largest winter resort for migratory birds in the Indian subcontinent.
The major management recommendations proposed for Chilika include de-weeding of grass thickets from Nalabana Island, implementation of a three months ban entry or check on disturbances to Panchakudi and Maladiguda islands from February to April, the breeding season of terns, according to findings of a comprehensive five-year study on visiting birds conducted by BNHS.
It may be noted here that the 15.59-sq km area Nalabana Island has been declared a as bird sanctuary as there is large congregation of winter migrant species in the area.
Operating Kondha nets around the borders of Nalabana Birds Sanctuary should be banned from November to April, which could be implemented through having a 5 month no-fishing buffer zone from the boundary.
Within this buffer zone, watchtowers need to be constructed to monitor and prevent fishermen from trespassing into the Sanctuary. These watchtowers could also be used by birdwatchers – general tourists are not permitted inside the sanctuary, the study on avian species proposed
Invasion of terrestrial vegetations (Cynodon, Salicornia) into the mudflats of Nalabana is a major concern for the conservation of long distant migratory shorebirds that prefer mudflats. As the mudflats of Nalabana is the only habitat for the critically endangered Spoon-billed Sandpiper Calidris pygmeusand several Near-threatened (Asian Dowitcher) and Vulnerable (Great Knot) wader species, emphasis should be given for the restoration of mudflats, the study opined.
As the causes of the proliferation of vegetations are not understood completely, the impact of silt deposition due to dredging must be investigated, especially since the proliferation is happening after the opening of the new sea mouths and commencement of ongoing dredging activity. The increasing number of water-bird species preferring grassland at Nalabana also corroborate the point, it said.
The BNHS’s multidimensional studies covered among other things the water bird ecology, population monitoring and distribution in relation to physical and biological parameters, migration, disease surveillance, and breeding ecology among others.
Chilika is one of the few wetlands in India which has species-wise bird population data for more than 15 years. This five year study has also generated information on the current status and movement pattern of most abundant migratory and flagship species, threatened and near-threatened bird species.
It was observed that the population of a few water bird species had undergone tremendous changes during the study period. The most abundant status occupied by Gadwall Anas strepera in the initial years was taken over by the Eurasian Wigeon Anas penelope in later years. The monitoring also showed a declining trend in the numbers of Northern Pintail Anas acuta and Northern Shoveller Anas clypeata. It also revealed an increase in the population of migratory Greylag Goose Anser anser, Bar-headed Goose Anser indicus, Glossy Ibis, Lesser WhistlingDuck, over the last four years, whereas the population showed a general decline in the two most common dabbling ducks (Northern Pintail Anas acuta and Gadwall) and also in major diving ducks (Tufted Duck Aythya fulgila and Common Pochard Aythya ferina). An overall decline since 2011 was also observed in Lesser Sand Plover Charadrius mongolus, Curlew sandpiper Calidris ferruginea, Little Stint Calidris minuta and Ruff Philomachus pugnax, this corresponding to their global decline, and due to the local climatic and ecological conditions. Six species of ground-nesting birds, namely Gull-billedTern Gelochelidon nilotica, River Tern Sterna aurantia, Little Tern Sterna albifrons, Black-winged Stilt Himantopus himantopus Oriental Pratincole Galreola maldivarum and Kentish Plover Charadrius alexandrinus that used 6 to nest in Nalabana Bird Sanctuary in the early 2000s have abandoned the sites.
River Tern and Gull-billed Tern had partially shifted to unprotected nesting sites like Panchakudi and Maldiguda in the Central Sector. Tagging studies also undertaken to provide information in elucidating their migratory movements or migrants through recoveries and re-sightings Neck-collaring studies revealed partial shifting of the wintering population in Chilika to other sites located further south in Tamil Nadu and Karnataka.
Strong site fidelity of migrants to Chilika Lake was demonstrated by re-sighting of neck-collared geese in four consecutive winters. Similarly, several color-flagged waders, viz., Black-tailed GodwitLimosa limosa, Curlew-Sandpiper, Little Stint and Common GreenshankTringa nebularia, Common RedshankTringa totanus were sighted in the subsequent seasons. Color-flagging studies revealed the movement of waders between Chilika and Point Calimere, and also the migratory movement of waders between Indian wetlands with the Yellow Sea of China and South Korea. Though the Indian subcontinent is the major wintering ground for the Central Asian Flyway populations, the linkage of Chilika with the East-Asian Australasian Flyway was established through the occurrence of East-Asian Australasian Flyway species such as Asian Dowitcher, Limnodromus semipalmatus,Great Knot Calidris tenuirostrisin Chilika, and the ringing recovery, color-flag and neck-collaring studies from Chilika and elsewhere. Ringing studies also further confirmed similar movement and the existence of site-fidelity to Chilika in several wader species through recaptures in the subsequent seasons. Large congregations (over 1,00,000) of Tufted Duck, recorded during the early part of the project in the open water zones of the Central Sector, were not observed during the later years.
Contrary to the declining trend among the common diving ducks, the rare and near-threatened diving duck, the Ferruginous Duck Aythya nyroca, showed an increasing trend, with counts of up to 200 birds. Among waders, the increasing trend observed for the globally Near Threatened Black-tailed Godwit in earlier years showed a declining trend from 2014. The decline was more conspicuous in the Mangalajodi and Bhusandpur marshes, the strongholds for this species in Chilika. The decline in Greater Flamingo Phoenicopterus roseus numberswas conspicuous during the current study, as was in the case of the earlier study (2001-2005). When compared to the population in early 2000 (between 3500 and 5000), the maximum numbers recorded during the present study was 1800 individuals in 2012-2013. In 2016, only 800 birds were sighted. The regular occurrence of Sanderling Calidris alba during both the onward (August) and return (April) migrations in Chilika was confirmed through this study. In 2013-14, highest counts of up to 250 individuals were recorded at the sea mouth. During the same time, more numbers of Vulnerable, Near Threatened and rare species such as Great Knot Asian Dowitcher and Red Knot Calidris canutus were recorded in Nalabana Island.