Thousands of birds flock to Nepal twice every year. Once in the winter, when it gets too cold for comfort in the northern countries like China, Russia and Mongolia, and once in summer, when Nepal offers an abundance of food for tropical birds.
Thus Nepal has traditionally been a safe haven for birds from two diametrically opposite climates. So much so that some species even choose to breed here, since the days are longer here, giving them more time to care for their young.[break]
Although it would seem that the migration of birds is instinctual response to difference in temperature, the reality is more complex. That there is science involved is evident in the V-shape flight formation that migrating birds prefer. Aerodynamically, this shape is known to be the most efficient. Individual birds take turns leading the group, because the one at the front gets tired due to the extra stress. Besides, birds are found to take the exact same routes over and over again through the years.
Some unguided groups of birds are also seen following the same pattern favored by their species. Birds that have been deliberately taken off course for studies invariably return to their homelands.
The mystery of how birds navigate long distances is yet to be deciphered, though it is speculated that they use various tools like mental maps, position of sun and stars, variation in temperature, color codes, smell, and the earth’s magnetic field. Some birds even learn the routes from elders who have flown before, indicating that culture is not unique to humans. Apart from obviously adding to biodiversity, migratory birds also have many seasonal functions.
They devour fast breeding insects, thus maintaining ecological balance. This year, the number of migratory birds coming to Nepal for the winter has decreased by approximately 20 percent, which is a cause for alarm from an ecological point of view.
Whatever method birds may employ to navigate, there is no doubt that yearly migration is an arduous task for them. Before they start, many species increase their food intake to build up a greater quantity of fat for the journey.
In Nepal, many birds like storks find such nutrition in the wetlands, where they already face conflicts with resident birds for food. With the wetlands of Nepal dwindling with every passing year, there is less and less food available for birds. When they cannot find food at their usual stopovers, many birds cannot complete the journey. Climate change, which has resulted in unnatural weather and vast geographical changes, has also bewildered many birds.
Elsewhere, light pollution in cities disorients birds that fly by night, and pollution in their annual habitat repels them. In the end, it is human actions that are affecting the migration of birds. If we do not pay attention to conserving the ecology at the earliest, soon we may be left with no birds flying into Nepal. That would be a very sad development for one of the most naturally gifted countries in the world.
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