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Video: The Birds — Rome's Hitchcock-ian problem

As Rome shoos away starlings, scientists study the mathematical precision of their flight.

European Starlings break their flock formation to roost atop trees in Rome’s center. Every winter, tens of thousands migrate to the city causing awe and alarm among residents. (Angelica Marin/GlobalPost)

ROME, Italy — Every sundown come fall, Rome residents witness an astounding spectacle, or, depending on how you see it, a scene out of an Alfred Hitchcock movie.

For a few hours after dusk, the sky above the city’s riverbank, piazzas and wealthy neighborhoods becomes plagued by thousands of European starlings zooming back and forth in fantastic tornado-like formations. Cacophonous calls echo throughout the city, as the dark-winged creatures soar through the air in sync.

“It’s very, very cool,” said Natalie Rozinova from Australia, as she covered her head with a map of Rome. “I don’t think I’ve ever seen that many birds in one spot, ever!”

But residents know better than to stop and stare. Rome’s pedestrians, along with roads, cars and monuments, soon become targets for a storm of droppings.

Besides complaints of a foul smell and rowdy nuisance, it turns out, starling excrement is a slippery street hazard. This has prompted the city of Rome to get rid of the spooky mob by beating them at their own game — scaring them out of the city.

“We recorded their cry for ‘danger, let’s leave!’ and we blasted it under their roosting sites,” said biologist Andrea Buscemi one evening as she walked along the Tiber River with a megaphone strapped to her back and an MP3 player hung over her shoulder.

“We wanted them to know that this isn’t a safe place for them to spend the night,” she said.

For the past three years, Buscemi and her crew of volunteer bird-busters have spent the month of November broadcasting these calls throughout the greenest neighborhoods in Rome.

Dressed in white surgical uniforms, the volunteers amplify the starling cry for three consecutive nights at a time in each location, hoping to shoo the birds out.

This scientific technique seems to work, at least for a while. But the European Starlings, which prefer nesting in urban and suburban areas, always return.

“We are sure that we’ll never manage to shoo them out of Rome completely,” said Buscemi. “We just want them to move a littler further away.”

These omnivores are native to Europe and have become infamous throughout the continent.

Traveling in flocks of thousands, the starlings migrate to southern Europe in the winter and feed on almost anything, including fruit and olive orchards, destroying local crops in the process.

Known for their aggressiveness, the second-cavity nesters are outnumbering local bird species, as they are able to lay triple clutches of their pale blue eggs in only one mating season.