Every year, between September and October, one can witness movement of birds in large numbers signifying the start of migration.
It is the annual dispersal of birds from the northern hemisphere to the Indian subcontinent including Sri Lanka.
When daylight shrinks and there is a shortage of food supply at the breeding sites, the birds take the cue and start migrating towards wintering sites in the South. The return journey begins in March or April.
While the shorebirds like waders and ducks, and raptors come from Siberia and Russia, birds like the European flycatcher, brown-breasted flycatcher, and barn swallow come from Europe.
Some birds are passage migrants, like the spotted flycatcher, rufous-tailed scrub robin, and European roller. They migrate through a large part of Western India and go to Africa to spend the winter there.
The amur falcons pass through India in December. The greenish warbler can be seen anywhere across Peninsular India.
The Indian pita that breeds in the Himalayan ranges migrates from Central India to the South to escape the harsh winters.
The pin-coloured common rosefinch from Himachal can be sighted at the Nilgiris often, feeding on grains by the roadside.
Pallikaranai in Chennai attracts a large number of flamingoes, varieties of ducks, and waders. Pulicat Lake on the Tamil Nadu-Andhra border hosts flamingoes whose numbers sometimes cross 50,000.
Huge numbers of ducks and waders can be seen at Chilika Lake in Orissa.
Other notable sites to see migratory birds are the Keoladeo National Park in Bharatpur, Rajasthan and Khijadiya Bird Sanctuary in Jamnagar, Gujarat.
This year, however, because of the COVID-19 pandemic, bird watchers are documenting migratory birds from their backyard.