On any given week,

given week, Dave Champagne can be found scouring the nooks and crannies of San Francisco

in an effort to hunt down one of the city's most notorious pests.

The worst jobs are the church steeples.

They're normally infested and you've got to suit up like a spacesuit to clean it.

They're smart animals. You know, if you have something

missing, a spike falls down, if you don't do something right, they find a breach

they will capitalize on it. Champagne doesn't deal with rats, squirrels, or termites. He's the owner of a company called

Bird Busters Incorporated. And one bird in particular makes up the bulk of his business.

Pigeons.

Yeah, now you think they're not too bright, but they're pretty tenacious considering they're still here.

Once they find a place to live, they're not going to leave.

It's estimated that there are more than 8 million pigeons living on the streets of

North American cities. Most of them are concentrated in busy urban centers. They gather an enormous

flocks in parks. They roost on roofs in light wells and under bridges. And their

acidic poop eats away at buildings, car paint, and solar panels.

Cities pay companies like Birdbusters millions of dollars a year to get rid of them.

But before pigeons were at pest, they were celebrated and even worshipped.

It's really only in England and America that we've seen them as so-called rats of the sky.

The reality is that it's a very, very gentle creature.

The only real problem is when there's just too many of them.

For the Freakonomics Radio Network, this is the economics of everyday things.

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