By Charlotte Owen
A murmuration of starlings is one of the natural world’s most impressive spectacles, eagerly anticipated, relatively easy to see and yet intriguingly mysterious, since we still don’t fully understand exactly how this fascinating phenomenon is achieved.
We do know why they do it, and it’s mostly about safety in numbers. Starlings are sociable birds and during the day they feed in small flocks scattered throughout the landscape. As the late afternoon light starts to fade, these flocks will regroup and head back to the communal winter roost site, where packing in tightly will help them to keep warm overnight. As more and more birds arrive, the flocks merge into a mesmerising murmuration that can contain thousands of individuals all swooping and diving in perfect unison. The incredible aerial display is maintained as the birds circle and swirl above the roost site, often over sheltered woodlands and reedbeds but also urban buildings and industrial structures, until eventually an invisible signal triggers the descent and everyone piles in for the night. The practical function of this deliberately dazzling behaviour is self-defence - a huge crowd of noisy birds that regularly returns to the same roost is an obvious target for hungry predators, but it’s much harder to pick out a single bird from a shape-shifting flock of thousands.
As to how starlings manage to achieve such amazingly co-ordinated flight, there’s a lot going on at once. Thanks to a reaction time of less than 100 milliseconds, each bird can make near-instant adjustments to their flight path. By constantly monitoring and matching the movements of their neighbours, directional information is rapidly and accurately transferred throughout the flock, maintaining cohesion. At the same time, the birds are attempting to sustain optimal flock density, gauged by the amount and angle of light that reaches their eyes, while also jostling for the safest position at the centre of the flock and trying to avoid being exposed to danger at the edges. The result is a synchronised swarm that not even a peregrine, the world’s fastest bird, can break - a truly extraordinary feat, and yet they make it seem so effortless.