In the winter season, the beautiful sunset over the Italian capital can suddenly go dark. Wide-eyed tourists and visitors gaze up in wonder, while the wary locals look down and run for cover.

Picture a Mediterranean sunset, and a gorgeous glow over one of the most ancient and beautiful cities in the world. Suddenly an ominous, dark cloud passes overhead, seemingly out of nowhere. The form moves in a strangely hypnotizing manner, turning left and right, swooping up and down, clearly not being controlled by any breeze. The locals immediately duck for cover or open their umbrellas. The beleaguered citizens of Rome in Italy know only too well what comes next – and it isn’t just a spot of rain.

These days, it is easy to think of nature as a fragile thing, easily contaminated and destroyed. And while it is true that ecosystems are sensitive to change, the natural world is also remarkably resilient and adaptable. After all, living organisms have had to evolve with an ever-changing Planet Earth from the beginning.

One way the world has changed in recent centuries is through humanity’s increased appetite for urban life. In Europe, this transition to predominately town-and-city living has happened over the duration of about a thousand years. And, of course, the phenomenon was greatly accelerated by the industrial revolution of the late-19th century. But, not only have people had to learn to adjust to this, wild animals have also had to find new ways to live in these man-made environments.

Nonetheless, some animals have positively thrived in these concrete jungles. The famous line has it that in a city you are never more than six feet away from a rat. To the great distress of many humans, these vermin can be found nesting just about anywhere walls are put up. Likewise, pigeons – often called rats with wings – have also made themselves so at home in urban centers that their populations are exploding beyond control.

Indeed, certain types of birds, such as pigeons, have easily adapted to city living. They make their nests in parks or in buildings, and scavenge off abundant food scraps. As long as their species is one that can tolerate pollution, noise and artificial light – not to mention human attempts to cull them – these birds can flourish within the urban hustle and bustle.

Nevertheless, some avian species are a little bit too successful at metropolitan living – at least as far as their human neighbors are concerned. One of these is the starling. As its name might suggest, the European starling is native to the southern and western parts of that continent. The collective noun for these migratory birds is a murmuration, and they can also be found in parts of Asia and North Africa.

European starlings, also known as common starlings, just love city life. Apart from an abundance of nesting sites, grassy areas, such as lawns, parks and outlying golf courses and fields, make for productive foraging. One city which hosts a large population of these birds for a few months a year is Rome in Italy.

Image: Marion Schneider & Christoph Aistleitner

Every year during the fall season, starlings make the journey from a cooling Northern Europe to warmer southern climates. Consequently, as many as four million of these birds alight on Rome for the winter. Feeding in the countryside during the day, the birds choose to stay in Italy’s capital city at night, drawn in by the warmer urban temperatures.

During these months, Rome’s feathery visitors put on what has been described as “nature’s greatest aerial display,” by the BBC’s Earthflight nature program. As the birds return to the city in the evening, huge flocks of starlings form what look like black clouds, sometimes big enough to blot out the sun. The huge groups of birds swoop and turn in amazing formation.

Such an airborne avian maneuver is also called a murmuration, and they are stunning and perhaps even a bit unnerving. The massed starlings are not just putting on a show, however. Murmurations are believed to be a defense mechanism. By rapidly changing direction in such a random way, the birds evade flying hunters such as sparrow hawks and peregrine falcons. In addition, the spectacle could deceive a predator into thinking they had come across a much, much bigger creature and take off in fright.

In 2012, a team from the University of Rome published a paper explaining how the murmurating starlings co-ordinate with one another. According to the study, the movement of each starling influences the seven closest birds around it. This leads to a chain reaction which enables the whole murmuration to move together effectively in complicated sequences.

But, while we may be seeing more of them these days, starling murmurations over Rome are by no means just a recent phenomenon. In ancient times, the movements were studied by Roman oracles who used them to make predictions. If the birds flew in certain patterns, that was taken as a lucky sign, while other variations meant people should take care – the gods were less than happy that day.

Many onlookers find the sight of the swarming starlings enchanting. There are parts of Rome where tourists gather to observe and film the murmurations. The locals, however, are not quite so enamored with the feathered show-offs. Having giant flocks of birds soaring above and dwelling below in your city definitely has its downside. And a rather messy and smelly one at that.

Indeed, the sheer amount of bird feces that accumulates in the capital of Italy during the starling season is a serious problem. “During their stay in Rome, the birds fly out in the countryside and eat olives off the trees,” Raffaella Mercolella, a local councilwoman, told U.K. newspaper The Guardian in November 2013. “So their mess becomes oily and more dangerous for mopeds, which have been involved in accidents.”

In fact, Rome’s occupants have had to resort to using umbrellas, or even just staying inside, to avoid being splattered by overhead flocks. And it is not just bird poop that is falling on people either. Uncoordinated starlings can also plummet from the sky, having collided in mid-air before dropping to their deaths.

In fact, Rome’s occupants have had to resort to using umbrellas, or even just staying inside, to avoid being splattered by overhead flocks. And it is not just bird poop that is falling on people either. Uncoordinated starlings can also plummet from the sky, having collided in mid-air before dropping to their deaths.

Inexplicably, there have been a great many cases of this of late, as reported by The Times of London in February 2018. The small, bloody corpses of the birds littered the streets of Rome. Much to the consternation of Francesca Manzia, who runs an avian hospital for the Italian League for Bird Protection. She told the newspaper, “It was like a Hitchcock film – there was a lot of blood and the smell became horrible.”

Curiously, autopsies run by Manzia’s organization showed that neither disease nor toxins were to blame. She suggested that predators may be behind the starling air smashes. “When attacked, starlings bump into each other,” Manzia explained to The Times.“If one starling hits an obstacle, many others will follow behind and meet the same fate.” However, the avian enthusiast admitted that this was just a theory.

But there is one fact that almost everyone can agree on. Whether dead bodies or feces, the citizens of Rome are sick and tired of cleaning up the starlings’ messes. A variety of methods to address the species’ over-population have been tried over the years, with limited success. Hawks were brought in to frighten the smaller birds, and megaphones blaring a “distress call” were employed to discourage starlings from roosting. Some frustrated Romans have simply resorted to banging on pots and pans.

Nevertheless, no permanent and effective solution has been found for the messy problem so far. Even if more drastic solutions, such as poisoning, were used, they are unlikely to keep starling numbers down. In fact, in culling the population, the remaining birds would only have more food and resources to rebuild their murmurations. So in the end, the residents of Italy’s capital may just have to resign themselves to slippery and stinky streets. In return, however, they are rewarded with some of the world’s most spectacular air shows.