Tens of thousands of songbirds were perched on trees, their constant chatter filling the warm air. If it weren’t for their singing and twitching, they could be easily overlooked as leaves on the otherwise barren trees.
As the last light shone through the sky, the birds took to the air, all at once. They moved as one big cloud of smoke, my eyes following the shape-shifting cloud as it magically transformed from a blob into a wave. The birds’ chattering faded as they drifted away from me, but before I knew it, it was back. The birds descended on the trees from which they had taken off, reinstilling life into the dead wood. After resting a while, they stirred and performed their aerial ballet once more, before returning to the trees to settle in for the night.
This synchronised ballet that some birds perform before roosting is called a murmuration. The birds I saw murmurating are a migratory species called the Rosy Starling. With a rose-coloured body, and shiny black wings and head, Rosy Starlings rain down upon India during the monsoon and leave in time for summer. I saw them when temperatures had just begun to soar, and realised that it may be a while before I see them again.
Back in their summer breeding grounds of Eastern Europe, the Middle East and China, rosys (as Rosy Starlings are often called) eat insects such as locusts and crickets. Adults feed their chicks only grasshoppers, which are rich in protein and other nutrients. In the process, the birds help in agricultural pest control. While here in India, they feed on fruits, and millets such as sorghum (jowar), earning them the moniker ‘Jowar Bird’. When palash (flame-of-the-forest) and silk-cotton trees are in full bloom, you can find them sipping nectar from their flowers.
Method to their madness
Rosy Starlings migrate, feed and rest in groups, but they are most conspicuous when performing their aerial display at dusk. Several ideas have been floated to explain this pre-roosting behaviour of starlings. Attracting more individuals to increase the warmth of the roost on cold nights is one. But the widely accepted idea is that starling murmurations are anti-predatory behaviours: it is thought that as more birds join the flock, the odds of each getting attacked by a predator go down. There are also more eyes keeping watch in a large flock. The huge undulating mass of birds can even confuse a predator as to which bird to focus on and attack without colliding with it and injuring itself.
These anti-predatory functions of starling murmurations have been explored in a species related to the Rosy Starling: the European Starling or Common Starling (which too overwinters in India, mostly in the north of the country).
A study of European Starling murmurations based on citizen science data revealed that murmurations were larger and went on for longer in the presence of birds of prey. This was especially true of murmurations with birds of prey flying too close or trying to attack. At the end of a murmuration, the birds were also more likely to nosedive into trees all at the same time, when a predator was around; in its absence, the flock would disperse.
Either way, the flock doesn’t have a leader guiding it – each bird plays a role. Given its size and the noise it creates, it wouldn’t make sense for the birds to await directions from one individual when a predator attacks. Research also shows that each bird in a flock interacts with its six or seven neighbours – this may be how starlings maintain order and not end up crashing into each other.
These aspects are known from studies in European Starlings or computer simulations of their flocks. Rosy Starlings, however, have been largely understudied. Perhaps, moving in a flock helps rosys too dodge predators that could make an easy meal of them. Maybe they too find safety in numbers like their cousins. Birds of prey such as Black Kites and Brahminy Kites did circle overhead when Rosy Starlings performed the ballet I was watching. At the end of it, the rosys settled on the branches, in thousands.
As I left behind the starlings still chirping away in the trees, I couldn’t help thinking about the background. They had staged their dizzying manoeuvres over a lake bordered by high-rise apartments and a busy road in urban Bangalore. Out on the road, a different kind of din was rising: made by members of my species heading to their own roosts.