ROME — This time of year in Rome, the evening sky is a marvel.

Just before sunset, there among the cupolas, starlings mass by the hundreds of thousands, performing an aerial dance. They dip and soar, bunch together and spread out. Seen from the ground, their ephemeral parabolas look like calligraphic brushstrokes.

But when the sun sets, the magic ends. The birds descend — and wreak havoc.

They spend their nights roosting, sometimes thousands to a tree and overloading the branches. They poop prolifically, and their droppings — thanks to their olive-heavy diet — are oily and slick. Those droppings can cause street closures and motorbike accidents. They can bury cars, bus stops, business awnings, even gravestones, under a Jackson Pollock coating of black and white.

“Abundant manure,” Rome’s environmental department called it in a report on the starlings.

Top: Starlings leave behind half-eaten pomegranates on the outskirts of Rome. Bottom: A bench is caked with starling droppings in the suburb of EUR.

The contrast between the transfixing 30-minute murmuration and the subsequent mess makes for an uneasy relationship between the starlings and their chosen winter home.

[Check out this flock of starlings doing laps around the National Mall]

For Romans, life would be a bit more convenient if the birds went elsewhere. But what’s become increasingly evident, amid attempts to manage the birds, is that the starlings have more say in the matter than the people do.

“It’s impossible to move that many animals,” said Alessandro Montemaggiori, an ornithologist at Rome’s Sapienza University.

Starlings are one of the world’s commonest bird species, but Rome stands out in Europe as one of their primary gathering points. The starlings have been migrating here annually since the 1920s, attracted by the mild climate. The traffic and paved surfaces and lights make it several degrees warmer than even the surrounding countryside.

The birds venture south from Germany, Hungary and as far away as Russia, arriving in October and November and remaining for a few months. During the day, they commute outside the city, seeking out farmland and olive groves.

Top: Starlings sleep in a pine tree in Rome’s Piazza dei Cinquecento, where buses help generate heat. Bottom: Electric lines along Raccordo Anuale, or Rome’s ring road, which runs through areas where starlings seek food in the morning.

They return to Rome, bellies full, soon after 4 p.m. They meet in the sky.

The birds move with such synchronicity that one pioneering British ornithologist, Edmund Selous, hypothesized that the starlings were telepathic.

Modern experts have concluded that the movements are not orchestrated by any one leader, but rather by a chain reaction of microsecond influences. Giorgio Parisi, a Nobel Prize-winning physicist, found that each bird interacts with six or seven other starlings in its immediate vicinity. In an interview, Parisi said the birds tend to move in a formation that resembles a “pancake.” But its shape-shifting appears more dramatic from the ground, depending on how the pancake is angled in the sky.

“It’s based on perspective,” he said.

[Why do flocks of birds swoop and swirl together in the sky?]

The murmurations work like signals to the returning birds — a way for starlings, which are highly sociable, to gather together.

Top: Ornithologist Alessandro Montemaggiori keeps a starling specimen on his desk. Bottom: Many Romans are fascinated by the birds and their aerial formations.

But they are also thought to have a defensive purpose. With so many birds swirling together, it’s hard for a predator, like a peregrine falcon, to lock in on any one target. Falcons are fearsome foes, capable of reaching 200 mph in the air. There’s a small population of falcons living year-round in Rome. Others migrate south with the starlings.

“When you see the starlings make these tight balls, that means there is a falcon next to them,” said Montemaggiori, the ornithologist. “It’s strength in numbers. That is their success.”

As the sun sets in Rome most winter days, small teams of workers put on white protective smocks and grab their bullhorns. They’re part of a program, deployed throughout Rome, to disturb the starlings and prevent them from roosting where they cause the greatest annoyance.

“If we can move them to a greener area, then that is a victory,” said one of the workers, Alexia Ferrantini, soon after she’d put fresh batteries in a music player connected to a bullhorn.

EUR, a suburb conceived as a fascist showpiece by Benito Mussolini that today serves as a hub for office headquarters.” class=”wpds-c-hcZlgz wpds-c-hcZlgz-bkfjoi-font-georgia wpds-c-hcZlgz-jDmrXh-width-mdCenter wpds-c-hcZlgz-iPJLV-css mw-md pb-md font–article-body font-copy ma-auto pl-sm pr-sm”>When The Washington Post embedded with a work crew in late December, the birds had taken to congregating in a particularly troublesome spot: EUR, a suburb conceived as a fascist showpiece by Benito Mussolini that today serves as a hub for office headquarters.

One late afternoon, the birds arrived above EUR in such numbers that they prematurely darkened the sky. By 4:35 p.m., they resembled an airborne tidal wave, and even then, more and more birds — returning late from their countryside foraging — kept joining the mass.

At ground level, crews waited to see which trees the birds would choose for their roost. At 4:58, the birds began descending in astonishing columns, crowding so thickly in the branches that it looked like certain trees had suddenly sprung to life.

Top: Workers with bullhorns set out to try to move the starlings to less troublesome roosts. Bottom: Starlings soar at sunset above the convention center in Rome’s EUR neighborhood.

The workers took off, aiming their bullhorns upward.

“Screeeeech. Screeeeech,” went the bullhorn soundtrack on repeat.

The noise was shrill, projecting a kind of guttural terror: It was a recording of a starling in distress. The noise echoed off the buildings so that all of EUR — in its full commuting buzz — seemed to be letting out eerie screams. The tactic worked: The birds, apparently sensing that one of their own was signaling danger, kept taking to the air, looking for new roosting spots.

“You can see they are agitated,” Ferrantini said.

Soon, the birds moved elsewhere.

[In the 1970s, the U.S. Army went to war with an unlikely foe: Starlings]

Starlings are common across North America, and Washington at one point even tried spraying eye-irritating fog into trees. (The solution proved only temporary.) Other parts of the world have found starlings so troublesome that they’ve tried to kill them off with poison. But experts say the birds are so adaptable, and have such short life spans anyway, that culling tends not to work that well.

Rome, since the 1990s, has used the recorded distress calls, a strategy devised by Bruno Cignini, a longtime leader of the city’s environmental department. Cignini borrowed a starling from a center that rehabilitates wounded animals, brought it to his office and recorded its noise as it reacted to the stress. Through trial and error, Cignini found the parts of the recording that registered more viscerally with other birds.

Typically, after three days of hearing the noises in a given spot, the starlings abandon the roosting site until at least the next season.

“Once they were chiefly in the city center, and now they’re being pushed a bit to the suburbs,” Cignini said.

In the 1980s, Montemaggiori said, some Rome administrators suggested trying to expand the falcon population as a way to contend with the starlings.

But it was quickly pointed out that falcons prey on only one bird a night.

“Can you imagine how many falcons we’d need?” Montemaggiori said.

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About this story

Design and development by Yutao Chen. Illustrations by Hailey Haymond. Graphics by Júlia Ledur. Story editing by Marisa Bellack. Video editing by Jason Aldag. Photo editing by Chloe Coleman. Design editing by Joe Moore. Graphics by Kate Rabinowitz. Project editing by Reem Akkad.

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