Or raccoons. It could be raccoons. Whatever's up there sounds bigger than squirrels. And I think they brought tools. Or maybe they're just taking chunks of the old brick chimney and using them as tools to dismantle the boards that we placed over the eaves the last time the raccoons decided to take up residence.
And now, so that I don't work myself into a stroke thinking about raccoons dismantling my roof (WHILE THE HOUSE IS ON THE MARKET!!!), I will postulate that maybe, there's just a team of them setting up a very innocent Rube Goldberg machine up there... that might account for the rolling bowling ball noise I'm hearing.
In fact, maybe in addition to the Rube Goldberg machine, there's a whole Varmint Amusement Park up there. Raccoons, squirrels and maybe a porcupine grabbing their burlap sacks, determinedly climbing a set of stairs (that they've also built) and sliding down the BIG SLIDE. Maybe some carnie-type raccoons smoking cigarillos underneath John Waters-style mustaches trying to knock up the pretty high school possums before they leave town. Maybe the next thing they set up will be THE AVALANCHE with loud rock music and the tattooed and pierced porcupine running it will yell,
"DO YOU WANT TO GO FASTER?!?"
And the varmints on the ride will squeal and shriek, "YEEEEEEES!!!"
(Except for those couple of possums who got bullied by their older siblings to go on the ride in the first place, who are screaming, "NOOOOOOOOOOOOOOOOOOOOOO!" as they cling to the sides of the ride for dear life.)
At which point, the neighbours will call to make noise complaints and we'll be arrested for disturbing the peace and running a Varmint Amusement Park without a license.