Ponyville was invaded by pigeons.

Nopony knew whence they came or why they stopped here. But they had multiplied thousandfold during a single night. Unfortunately, Ponyville had almost no tree where they could nest. So they had roosted on what was available: sills, gables, roofs, rafters, attics…

Everypony loved birds. Robins,  thrushes, swallows, nightingales were the favourites. However, pigeons had a bad habit: they cooed.  They cooed all day and some even at night. While that was (at a pinch)  bearable during the day, Ponyville’s quiet nights had turned into a nightmare for whoever wanted to sleep.

But that was not the biggest problem, as earplugs could help dampen the ruckus. No, the biggest problem was way worse.

Pigeons shat. Outside in the streets, inside the houses. Everywhere. They shat.

In the course of three days, the greenish, gooey splotches dropped by those flying critters had covered most of the town. Everypony set about cleaning the muck. But not only scrubbing it off turned out to be a gruelling challenge, in the end all those efforts amounted to nothing: within hours, the same splotches had returned. 

Each type of pony reacted differently to this new nuisance. While pegasi got away with it easily by flying high enough, unicorns soon took to teleporting from house to house, avoiding the streets. Less fortunate, the earth ponies – well – had no choice but to walk under large umbrellas.

Roseluck fainted when she discovered her flowers “spruced up”. Rarity, after fighting a whole day to protect her most precious attire, locked the boutique up and moved her collection to Manehattan. Applejack retreated into her cellar with her cherished apples. Twilight Sparkle had to cast a cleansing spell each hour to keep her castle clean. Pinkie Pie shut herself in her attic, scaring the birds with her party cannon. Only Fluttershy’s cottage remained inexplicably unspoiled.

Major Mare called an emergency meeting. All assembled in town hall, praying that no bird would make its way inside while the gates were open.

The major asked if anypony had an idea to get rid of the plague.

“I do,” Twilight Sparkle said.

“What is it, Princess?” Major Mare asked.

“An ultrasound amplifier. It will frighten the birds away, while being inaudible to ponies.”

Major Mare nodded. “Sounds good. When will it be ready?”

“Tomorrow morning.”

“Excellent! Let’s do this.”

Everypony in the hall nodded.

[hr]

The next morning, Twilight, carrying with her a complex contraption, materialised in Town Hall’s square. Right away, she flicked several switches and pulled a couple of levers.

Nothing happened. The birds didn’t flinch.

“It doesn’t work,” Major Mare grunted.

Twilight Sparkle simpered. “Err… Just a minute,” she squeaked. She fumbled with the levers, turned buttons clockwise, counterclockwise, craning every so often to see whether the birds reacted or not.

They did not.

Half an hour of fidgeting later, beat and crestfallen, the alicorn cut the power off and gave up.
 
 [hr]
 
“Does anyone have a better idea than Princess Sparkle?” Major Mare grated.
 
Nopony raised a hoof. The silence in the hall was ominous.
 
“Ahem!” a flimsy voice squeaked in the last row.
 
“Fluttershy?” Major Mare blurted. “Yes?”
 
Fluttershy stood up, coughed. “What if… I asked my kestrels to bring around other kestrels and… and they… maybe they could settle in Ponyville for a while. Kestrels feed on pigeons…” 

“Would your kestrels kill all the pigeons?” said Major Mare, recoiling at the prospect of picking up hundreds of strewn carcasses.

“No, no,” Fluttershy spattered. “When they’ll spot the kestrels, the pigeons will flee, as preys confronted to predators do.”

“Any objection?” Major Mare asked. She scanned the crowd, but no one protested. “Then what are we waiting for?” she concluded, slamming a gavel on the lectern.
 
 [hr]
 
It took a few hours for Fluttershy’s kestrels to round up others of their kin. Once they were a dozen, they darted from Fluttershy’s cottage to Ponyville. 

The effect was immediate. As soon as they caught a glimpse of the kestrels, the first pigeons took off, and their panicked squeals spread like wildfire. Soon, a flock of thousands of pigeons was flying away, to the cheering of everypony. 
Ten minutes had sufficed to eradicate the pests from Ponyville.
 
Fluttershy was celebrated. Major Mare decorated her, and Pinkie Pie threw a mega-party in her honour. 
 
It was also decided to keep a couple of kestrels in the spire of the town hall, just in case.

[hr]

Ponyville was invaded by kestrels…