Migratory birds in wetlands of Assam

Gunin Borah

(The writer is from the Faculty of Geography, Biswanath College, Chariali. He can be reached at Email ID: borah.gunin@gmail.com)

The birds who migrate from one location to another to breed, feed and raise their offspring are known as migratory birds. They usually migrate from unfavourable locations to some favourite places which are having suitable conditions along with sufficient food and water resources and are safe as well. The majority of the birds migrate during the breeding season and others migrate for food resources and because of changing seasons.

Avian migration is a natural phenomenon. Migratory birds fly hundreds and thousands of kilometres to find the best ecological conditions and habitat for breeding, feeding, and raising their young. When the conditions at breeding sites become unfavourable, it is time to fly to regions where conditions are better.

There are different migration patterns of birds. The majority of birds migrate from northern breeding areas to southern wintering grounds. However, some birds breed in the Southern part of Africa and migrate to northern wintering grounds, or horizontally, to enjoy the milder coastal climate in winter. Other birds reside on low lands during the winter months and move up a mountain or high altitude for the summer.

Migratory birds have the perfect morphology and physiology to fly fast and across long distances. Often their journey is an exhausting one, during which they go to their limits. The Red-Knot has one of the longest total migration routes of any bird, travelling up to 16,000 kilometres twice a year. It breeds in Siberia and overwinters on the west coast of Africa, some even going down to the tip of South Africa.

It is amazing how migratory birds can navigate with pinpoint accuracy. Exactly and properly how migratory birds find their flyways is not fully understood. It has been shown that they can be orientated by the Sun during the day, by the stars at night and by the geomagnetic field at any time. Some bird species can even detect polarized light, which many migrating birds may use for navigation at night.

Aviation migration is one of the most common migrations or movement patterns that are seen in birds that happen from North to South or East to West or vice versa. It also happens during seasonal change or movement between breeding and non-breeding locations. Migration is not easy and costs a lot. The birds have to cover long distances to reach their destinations and during these journeys, they need a lot of energy, food, water, sufficient rest, etc., and not all the migration journeys become successful and some of the birds die as well in these journeys.

Different birds migrate at different timings, but most of the birds prefer to fly at night because usually, the night is much safer for them due to having cooler air at night with which they can fly and rest easily. They prepare for their return as well, because after exhaustion of their whole energy in the long-distance journey they usually feel hungry and require food and water.

The Brahmaputra valley in Assam has a distinctive natural environment that depends largely on wetlands. The innumerable freshwater lakes, (beels), ox-bow lakes, marshy tracts and thousands of ponds and tanks hold water almost throughout the year and are vital to water needs and food production.

Besides, these serve as habitats for thousands of species of flora and fauna. The protected areas or national parks along the Brahmaputra include the Dibru-Saikhowa National Park, Kaziranga National Park, the Laokhowa-Bura Chapori Wildlife Sanctuary, the Pobitora Wildlife Sanctuary, and Orang National Park are significant habitats for the migratory birds.

The several networks of connecting streams and small rivers that run from the hills, through the forests and then to the Brahmaputra, each also form an ideal habitat for waterbirds, both resident and migratory. From the marshes of Kaziranga, Neemati, Majuli, Dibru-Saikhowa, Joysagar, Panidihing Birds Sanctuary, to Deepor Beel in Guwahati, birds delight at the blissful sight of thousands of migratory birds.

Assam State Remote Sensing Application Centre has identified 3,513 wetlands in the state about 9.74 per cent of the state area varying from 2.50 hectares to 882.50 hectares of area coverage. The state's natural wetlands, swamps, or marsh have a share of 42.9 per cent.

Every year during winter Assam gets an influx of millions of migratory birds from different corners of the world. The Brahmaputra river and its tributaries, riverine lakes, and beels play host to the migrating birds, because of their beautiful location and habitat condition. Over 300 species of birds take shelter at the edge of the river making it a sightseeing spot for tourists and other visitors. The birds migrate from winter hit regions Europe, Siberia, Antarctica, North America, Russia, Central Asia etc. Various types of water birds like Greylag Goose, Ruddy Shelduck, Geese and Swans, Cranes and Rails, Storks, Ibises and Spoonbills, Flamingoes, Gulb, Terns, Skimmers, Pelicans, Pintail Duck, Indian Spot-Billed duck, etc are seen visiting the river banks of Brahmaputra. The birds are ecologically dependent on wetlands for at least a part of their annual life cycle.

Deepor Beel near Guwahati, a permanent freshwater lake, was home to different species of birds before the establishment of the bird sanctuary. The sanctuary is a great food source and breeding ground for a large variety of residential water birds as well as several migratory birds.

Nowadays, many wetlands are drying out, getting silted over or being encroached upon and some 1,367 are facing serious threats to their existence. The natural wetlands are declining rapidly.

Several factors have been responsible for the rapid decline in the wetland ecosystem, including urbanization, siltation, overfishing, human interference, land and water grabs, decrease in freshwater inflow, choking of lagoon mouth due to silt, etc. So, the common people of the migratory bird's site awareness about the need to protect migratory birds and the habitats they rely upon, have become very urgent to balance the needs of conservation against the needs of local communities living around the wetlands.