Why sparrows crowd Dhaka's roadside trees at dusk despite lights and horns

As evening falls, flocks of house sparrows crowd the bakul trees on the Panthapath road divider in Dhaka. The same scene plays out from Science Lab to Shahbagh, on roads in Uttara and around Jamuna Future Park. Trees that look empty by day become a night shelter and empty again at dawn.

Prof ANM Aminur Rahman, a bird expert at Gazipur Agricultural University, told The Daily Star that sparrows gather in trees overnight outside the breeding season, behaviour known in ornithology as roosting. They often return to the same tree, which can stay their night address for a long time.

Safety is the main reason, he said. Dense branches shield them from wind, rain and predators. In a group they sense cats and owls sooner, and one bird can alert the rest. Staying close at night may also help them keep warm.

In the breeding season the birds pair up and large night flocks are less common. He has seen the same behaviour outside Dhaka, in Sirajganj, along the Cumilla-Chattogram highway, in Kishoreganj and on the Sylhet road.

Mokarram Hossain, a writer on plants and nature and general secretary of Tarupallab, said birds look for places where they are unlikely to be caught or disturbed and where food is at hand. The reporter is Fahima Kaniz Lava.

Source: The Daily Star