A group of crows is called “a murder.” That may be reason enough not to want 10,000 of them around at once.

But there are other reasons, too. Just ask officials at Pitt, where, after years of contending with hordes of migrating winter crows, there have been no bird-perpetrated homicides but plenty of smelly and slippery messes left on sidewalks.

It’s a visual fitting of “The Birds.” The school’s response has been more “Home Alone.”

Defense starts around sunset, with the steady, cacophonous cawing of birds unseen. Outside the Cathedral of Learning on Friday, the sound was powerful enough to be clearly detected from inside a moving vehicle. It evoked mental images of a bar fight between seagulls.

Joe Miksch, director of media relations at the university, said it’s actually the recorded sound of owls and hawks — known predators of crows.

For several years, Pitt has dusted off CDs each fall — when murders begin to roost — that contain the adversarial avian voices. The discs are broadcast using CD players wired to speakers and positioned around campus as needed. (Apparently Spotify has yet to fill this niche.)

Here’s what that sounds like:

Miksch said the move was recommended by the National Aviary and Penn State. The latter has had its own public battles on this front, utilizing fireworks — aka “bird bangers” — and lasers in a targeted campaign described by the school’s Office of Physical Plant as “periodic crow harassment.”

Pitt’s anti-crow campaign also involves “limited use” of “holiday laser lights,” Miksch said.

So far, at least, the combination appears successful.

“The idea is to nip it in the bud,” Kate St. John, a bird expert and author of the Outside My Window blog, told The Incline. “If Pitt can worry them away now, then they won’t be a really big problem with 10,000 of them in late December.”

A January 2017 article in The Pitt News described undergrads dodging crow feces as it rained down from the sky.

But why are they here, or, more to the point, why are there so many in one place?

Crows are smart — scary smart. They’re also definitely not above eating garbage. In the winter, they migrate out of cold, foodless zones and hit the cities, where there’s plenty of garbage to eat, trees or perches to roost on, and sidewalks to poop on.

As for why they gather in such large numbers, there are various theories. Some involve a strength-in-numbers benefit, others a willingness to share the choicest real estate.

“They start in late October, building and building. They’re coming from the north somewhere. These are not resident [crows], and they won’t stay beyond late February,” St. John said.

But that’s little consolation to Pitt or its feces-dodging students.

“When you’ve got 10,000 pooping crows in the trees around the Cathedral of Learning and Heinz Memorial Chapel, it doesn’t smell good, and it’s slippery when wet, and by the end of December, they have a real issue,” St. John added.

So Pitt rolls out its audio scarecrow each year at this time. It’s an annual tradition, a sure sign that fall has fallen. And while the birds are supposed to be bothered, Miksch said he was unaware of any human complaints about the noise.

There’s a slight chance, however, that the birds get wise to all this. Again, they’re very, very smart.

“They can get used to these things and decide ‘Oh, what the hay, I hear this all the time, it’s nothing,’ St. John explained. “Crows are like monkeys with wings …”

In recent decades, the birds’ presence has grown in cities across the U.S. as they’ve been targeted by hunters and uprooted by rural development. And it turns out they like cities a lot: there’s plenty of garbage to eat and plenty of places to roost.

As National Aviary Ornithologist Bob Mulvihill told 90.5 WESA in September, crows prefer to roost in trees near low-level artificial light and like spots that are warmer, making densely-populated areas with manmade sources of heat, like Pittsburgh’s East End, ideal. All this is to say that even if Pitt manages to scare the crows away, they’re not going far.

And if Pitt doesn’t drive them off, they can always be trained to pick-up litter or adopted as a new mascot.

No crows were harmed in the making of this article.