Every winter, the skies over Italy's capital are filled with the mesmerising sight of thousands of starlings swooping and diving in unison. But when they stop to rest on treetops, their droppings coat pavements and cars below - prompting the city authorities to scare them away.

"We act on their fear by using their own alarm call," says Marianna Di Santo, a member of the Fauna Urbis task force. Clad head-to-toe in white protective clothing, she waves a speaker emitting a series of sharp cries, emulating the natural alarm call of the birds.