dead birds
Dead starlings in Rome
The flocks of starlings that create choreographed patterns in the skies over Rome have mysteriously lost their aplomb, with hundreds falling to their deaths after colliding with each other

The birds began plummeting from the sky last weekend, leaving a litter of tiny corpses across roads and pavements. Normally, they weave intricate shapes in the sky, twisting and turning in formations known as murmurations to deter predators while providing a show for locals.

But at Porta Pia, one of the gates of Rome, and in other neighbourhoods, residents had to tiptoe around fallen birds' bodies, while mopeds risked skidding on corpses crushed by passing cars. "It was like a Hitchcock film — there was a lot of blood and the smell became horrible," Paolo Peroso, head of the Porta Pia residents' association, said.

Hundreds of starlings fall from the sky in Rome
Hundreds of starlings fall from the sky in Rome
Millions of starlings migrate south during the winter to Rome, where they enjoy the warmth and the street lights that allow them to keep an eye out for predatory falcons. During the day they venture out of the city, feasting on olives before roosting in Rome's plane trees and dumping tonnes of oily excrement on the streets, forcing locals to carry umbrellas.

Early tests on the dead birds ruled out poison or disease, said Francesca Manzia, head of a hospital run by the Italian League for the Protection of Birds. "We found they were in good health but suffering from the trauma and broken bones you would associate with collisions, either with each other or with cables," she said.

An abnormally large number of starlings heading for the same trees could have led to the collisions, while another cause could be attacks by predators, which create panic within the murmurations, she said.

"When attacked, starlings bump into each other and if one starling hits an obstacle, many others will follow behind and meet the same fate."

Ms Manzia said the true cause of the deaths was a mystery, just as the exact way the birds co-ordinated their murmurations remained a puzzle for scientists. "We don't really know what they are doing," she admitted.