MIRZA, March 19 - Every winter, thousands of migratory birds visit the Brahmaputra river and take shelter on its islets as well as nearby waterbodies.
This season too, the first arrival of migratory birds to the Brahmaputra in Kamrup district was reported in early November and it is believed that the birds may start departing during the last week of March.
The migratory birds after flying for several thousands of kilometres from the cold regions of Europe, Antarctica, North America and even from Siberia, have transformed the Brahmaputra river, its islets and the surrounding forests into a heaven for bird lovers.
According to The Book of Indian Birds written by noted ornithologist Dr Salim Ali, migratory birds use several methods to navigate during migration.
Many birds use celestial navigation and some even detect the positions of sun, stars and moon to locate their destination. Some birds can even detect ultraviolet radiations emitted by the sun, while some birds use topographical landmarks such as mountains, river valleys and forests during migration.
Seabirds identify their destinations by characteristic odours. Some birds even possess echolocation and can be guided by echolocation technique.
Several varieties of water birds such as bar headed goose, northern pintail, northern shoveller, gadwall, common green shank, yellow wagtail, common teal, black winged stilt, ruff, wood sandpiper, spotted sandpiper, Eurasian wigeon, shrike, Ruddy shelduck (also called chakoi chokowa), common shelduck, red crested pochard, grey leg goose, common pochard, pintail duck, mallard duck, common tern, large egret, black-necked stork, great cormorant have taken shelter here.
Reports said some endangered and threatened birds like oriental darter (Anhinga melanogaster) have visited this time. Sources said predator birds such as grey headed fish eagle, pallas�s fish eagle, hen harrier, Eastern imperial eagle have also been seen.
These migratory water birds have been visiting the Brahmaputra and other water bodies during the winter from cold countries, as there is little food there during the winter and the temperatures also dips. Sources said a significant population of migratory birds also visit the India�s warmer southern region, Sri Lanka and Pakistan.
Sources said that over 200 species of migratory birds come to India in search of feeding grounds and also to escape the severe winter weather in their native habitats in Europe, Antarctica, Russia, etc. Some birds such as Asian Koel, black crowned night heron, Eurasian golden oriole, comb duck, blue-cheeked bee-eater and cuckoos visit Assam the during summer too.
A few years back, large flocks of migratory birds were seen on the islets and edges of the Brahmaputra river, but their population is decreasing year after year.
Indiscriminate fishing, poaching, human disturbance and largescale agriculture activities are adversely affecting the habitat of migratory birds.
An office bearer of a leading environment NGO said that the swimming of birds in the river helps in penetration of sunlight deep into the water by breaking the unnecessary surface film.
The penetration of sunlight helps in growth of zoo plankton and plant plankton, which are the main sources of food for fish. The growth of fish helps the birds, which are in turn beneficial to mankind.