In the Roman twilight1, nature's great dancers flock to the stage.
The acrobatic twirls like wisps of smoke.
A synchronised spectacle of breathtaking beauty.
The starlings migrate in winter, south to Africa, nesting at night in central Rome for warmth, flying in formation to avoid predators2.
A murmuration it's called, and this city of art marvels3 at the show.
这便是所谓的 “椋鸟群飞” 现象，这座艺术之城对这场空中表演拍案叫绝。
But beneath their charm, Rome is rotting, and it's a hell of a mess.
Mark Lowen, BBC correspondent
In the cold light of day, the other side of these gorgeous birds is clear. And for those unlucky enough to be in the wrong place at the wrong time, it is not exactly sightly, it can be a safety hazard, and I can tell you that even with a mask, the stench is rancid.
"I slipped on the droppings when it was muddy," this man says, "the world has invented everything, just not bird underpants!"
Beside the ancient forum4, a new attempt to try to solve the problem.
City officials shining lasers onto trees, which the birds dislike, prompting them to move on.
The project is focused on Rome's tourist heart, in a bid to clean up its image.
Marco Leva, Environmental Officer
This doesn't cause the birds any stress – it's more like a nuisance for them. I do this work, but I'm actually a nature lover. We're not stopping them from sleeping, we're just telling them to find another location, and it works -– this tree used to be completely full, and now there are about ten percent of what there were.
In ancient Rome the starlings were seen to augur5 the gods' wishes. Centuries on, these dazzling creatures keep visiting. How man and nature can coexist is the eternal problem of the Eternal City.