Migratory birds
Liton Rahman / driknews
Bird migration is the usual cyclic flight undertaken by numerous species of birds. Bird movements take in those made in response to changes in food availability, habitation or climate. Migration is marked by its annual seasonality. On the contrary, birds that are non-migratory are assumed to be sedentary or resident.
Bangladesh is a favourite place for many migratory birds, especially some of the exotic places such as the campus of Jahangirnagar University, National Monument and many more. People tend to visit those places to enjoy the movement of these pretty visiting birds. We are lucky to receive these seasonal guests.
However, human behaviours have threatened lots of migratory bird species. The distances concerned in bird migration indicate that they frequently cross political boundaries of countries and conservation measures require global collaboration. A number of international treaties have been signed to conserve migratory species including the Migratory Bird Treaty Act of 1918 of the US and the African-Eurasian Migratory Water bird accord.
The concentration of birds during resettlement can put species at risk. A number of stunning migrants have already left extinct, the most distinguished being the Passenger Pigeon. Hunting along the migratory route can also take a heavy toll. The populations of Siberian Cranes that wintered in India declined because of hunting along the route, particularly in Afghanistan as well as Central Asia. Birds were last seen in their favourite wintering grounds in Keoladeo National Park in 2002.
Structures such as power lines, wind farms and offshore oil-rigs have also been known to have an effect on migratory birds. Surroundings annihilation by land use changes is nevertheless the largest threat and shallow wetlands which are stopover and wintering sites for migratory birds are mostly threatened by draining and reclamation for human use. To invite these seasonal guests and provide them the best hospitality, the ideal conditions have to be retained.
Source: The Daily Star, December 30, 2009
