ROME (Reuters) - Dressed from head to toe in a protective white suit and face mask, Fabrizio Zani is paid to prevent Rome's birds from getting a peaceful night's sleep.
As millions of starlings dart above the Vatican, Zani and a dozen colleagues prepare an ear-splitting racket to try to keep away the creatures which descend on Rome each autumn from northern Europe.
With a flick of a switch, a shrill sound -- to the human ear somewhere between a rusty barn door opening and fingernails dragging down a blackboard -- blasts out.
It is a recording of the starlings' own distress call, amplified hundreds of times.
In the confusion that follows it's impossible to tell if the birds are actually bothered by the row. But people hurry away, looking back in incomprehension, grimacing at the birds' stench, or shielding themselves with umbrellas from bird droppings.
"We use a different cry each day," said Giovanni Albarella, coordinator of the starling squad run by the Italian League for the Protection of Birds (Lipu) which runs the scheme and has recorded a dozen different bird cries.
"It's all about fooling them," he told Reuters. "The trick is to make them think they are in danger."
Rome is not alone in its battle. London has used hawks to actually kill pigeons in Trafalgar Square, while in New York's Times Square authorities also used a noise-making device to scare away birds in 2006.
A hazard to walkers, motorists and some of the world's most treasured monuments, thousands of the starlings earlier this month forced a Ryanair passenger jet to make an emergency landing at the city's Ciampino airport.
Although shaken, the passengers were unhurt. About 200 of the birds bloodied the jet's nose cone.
On their own the birds, which each weigh about 80 grams (3 ounces), are not much danger. But when flying in flocks so dense they can block out the sun, they are a hazard and their stench is like a poorly cleaned cage at a zoo.
The white guano dripping like tears down the face of a statue of the poet Trilussa in the pub-filled Trastevere quarter is testimony to the scheme's limited success -- though the group argues it is the best they can do.
"Obviously we don't have a magic wand. We can't make the birds disappear," said Albarella. "If you kill them, they will soon be replaced, so it probably wouldn't work."
Stone bridges across the river Tiber are still coated in hardened excrement. In a sidestreet, cars and scooters are caked in it. Some Romans protect vehicles parked for more than a couple of hours with plastic sheets.
Rome's leaders decided about 13 years ago that the starling problem was best tackled, not by trying to poison or shoot them, but by scaring them into the countryside or Rome's large parks.
At a cost to the city of some 120,000 euros ($150,200) each season, the squad moves around Rome to where the birds return from a day's feeding in the countryside. They are attracted by the relative warmth and lack of predators in the city's trees.
At times Rome's starling population can reach five million -- more than in any other Italian city, according to Lipu.
"There are too many and they are all over, pooping everywhere," said Ann Berry, a young American tourist.
Blasting noise at dusk for three days in a row thins the birds out, but many remain. Others fly on to different parts of the city where the process begins again.
Members of the squad cover themselves from head to toe in neon-striped overalls before starting a shift.
"The suit's to keep off the bird poo," said Zani's colleague Roberto. "The luminous stripes are so the cars can see us and the mask is for the smell.
"There's an accumulation of guano which creates a soapy substance in the rain, creating a risk for scooters."
Experiments in Belgium and the United States, with methods varying from poison to dynamite blasts, have proved less successful, Lipu says.
In addition to the mobile starling squad, it has installed strips of luminous material and permanent sound systems in some trees to increase the birds' discomfort.
Despite the Ryanair incident -- which airport authorities are still investigating -- the airport's bird-scaring system usually works, they say.
"The situation at Ciampino is pretty good when it comes to bird strikes," said Claudio Eminente, head of the civil aviation authority's bird strike committee.
But not all Romans are satisfied. Groups representing residents near the airport say the incident is further evidence air traffic over their homes should be curbed. Some living near the center are also still unhappy.
"They've never really tackled this," grumbled resident Maurizio Barberi as he strolled along the river. "They should really cut back the trees."
Additional reporting by Will Russell; Editing by Catherine Bosley and Sara Ledwith