The backstory of a bird paradise in Andaman and Nicobar

The land changes due to the 2004 tsunami created wetlands that is now a haven for birds in the Andaman and Nicobar Islands

Map from the study published in Journal of Threatened Taxa showing the wetlands after tsunami.

A flock of Andaman Teals at Sippighat. Credit: T R Shankar Raman /Wikimedia Commons

Pheasant-tailed jacana in the wetlands. Credit: Neelam Purti

Cyclones, floods, landslides, earthquakes, volcanoes and massive tsunamis— the Andaman and Nicobar Islands have endured it all for millennia. However, the 2004 Indian Ocean earthquake, which originated in northern Sumatra, Indonesia, stands out as one of the deadliest natural disasters to hit the archipelago in recent times.

The tremor shook the land for a good ten minutes. About 50 metres deep inside the ocean, the Burma Plate and the Indian Plate broke apart, rupturing the ground for about 1,600 km—almost the distance from New Delhi to Hyderabad. The enormous waves of the tsunami, some as high as 10 metres, washed away lives and livelihoods on these islands.

"There were a number of aftershocks that resulted in a change in the geomorphology of the islands," says V Shiva Shankar, a geospatial consultant and a guest faculty at the Andaman College (ANCOL), Port Blair. Parts of the Nicobar Islands and South Andaman Islands sank by around 1-1.5 metres. Islands in the northern and middle Andaman rose by the same amount. With water flooding the subducted parts, these land changes created a unique wetland ecosystem. About two decades later, it is now a bird paradise.

In a recent study, published in the Journal of Threatened Taxa, Shiva Shankar and his colleagues counted birds in six such tsunami-created wetlands in the Andaman Islands: Stewartgunj, Ograbraj, Sippighat, Wandoor, Chidiyatapu and Carbyn's Cove. They chose these spots because satellite images revealed the greatest degree of changes in landforms in these areas.

Between November 2018 and March 2020, the researchers recorded over 63 bird species of birds in these wetlands, including the Andaman Teal (Anas albogularis) and Andaman Crake (Rallina canningi), which are found only on the archipelago and nowhere else in the world. Although the researchers had anecdotally seen an increase in the number of birds in these wetlands, this was the first study to count their precise numbers.

Andaman and Nicobar Islands are a biodiversity hotspot teeming with unique plants and animals. "Most flora and fauna here resemble that of the Indo-Malayan regions," says Neelam Purti, a forest ranger in the South Andaman Forest Division and an author of the study. "As the islands are isolated, you can find most endemism in birds." The Narcondam hornbill (Rhyticeros narcondami), found only on Narcondam Island, is one example.

Out of the 572 islands of the archipelago, only 37 are inhabited by people, leaving many pristine islands for other forms of life. The islands are home to nine national parks, 96 sanctuaries and one biosphere reserve. So, it isn't surprising that the study found a wealth of birds in the wetlands. However, it is the first to understand how the tsunami changed the bird diversity over time.

Mangroves become wetlands

The now-sunken parts of the islands had mangrove patches that shielded the islands from much of the tsunami's devastating effects. They were also the abode of wetland birds. However, as water flooded into these subducted parts post the tsunami, the mangroves died. Satellite images show that in Ograbraj, the tsunami completely wiped out the mangrove patches, while in Sippighat, less than a third of mangroves survived. Interestingly, in Carbyn's Cove, all of the mangroves were spared.

When the wetlands were newly formed, the saline water and poor aeration of the soil did not allow plants to grow. But, as the nutrient-rich sediments started flowing in, some shrubs, ferns and herbs began to take root. The inundated area became a breeding ground for fish, shrimps, crabs, molluscs, snakes and frogs. "A food chain was developed," says Shankar. With the plants providing nesting grounds and the water providing food, the birds eventually returned.

Today, they are thriving in these tsunami-created wetlands, which are favoured birding spots. "The grasses that have grown in swampy areas have become food for them," says Purti. "They just pick the young shoots with their beaks and use the dried grass to make their nests."

The study found that wetlands in Ograbraj and Sippighat had the highest bird diversity as they were rich in food sources. On the other hand, Carbyn's Cove and Wandoor, where tourist vehicles and fishing boats are frequently seen and are close to human settlements, recorded the lowest bird diversity.

Of all the birds recorded in the six wetland areas, about half were shorebirds like terns and plovers (Charadriiformes), followed by large fish-eating birds like herons and egrets (Pelecaniformes), and medium-sized crakes, coots and moorhens (Gruiformes).

The birds have also invited an unusual predator into the wetlands. "We happen to find a lot of the saltwater crocodiles (Crocodylus porosus) in those regions," says Purti. "Because they get an easy snack—birds and their hatchlings."

The mangroves that were further in the sea before the tsunami have been migrating towards the coast with the tides and anchoring in the wetlands, in the recent years. "If we let the mangroves be, it will become a huge patch," says Shankar. But, human activities don't make it easy for the wetlands.

Old threats to the new wetland

Land reclamation is proving a threat to the tsunami-created wetlands. "People have pushed out stagnant water and have refilled the wetlands with soil," says Purti. They have cut most of the mangroves and have sold the reclaimed land for commercial establishments and tourism-centric development.

With the new buildings come communication towers, which interfere with the birds' migratory paths. Human disturbance is also taking a toll on the birds. "When we are breaching their privacy, obviously there will be fragmentation in the whole ecosystem," says Shankar.

The outcomes are already showing: the birds have started migrating from Sippighat to adjacent wetlands, where reclamation is in full swing. "We can't do anything because they are in private holdings," Purti says. The researchers call for the conservation of these wetlands that provide a safe haven to the winged residents.