Can my cat break my window with his tail?

So lately a feral cat (or someone's cat who just stay outside all the time), has discovered the window my cat likes to hang out by. I keep the blinds up and the kitty tower by this double window so my cat can get sunlight, watch the backyard, etc. Now, at various hours, I'll hear a loud knocking sound coming from the bedroom which means the feral cat is outside and my cat is on the windowsill making some sort of hiss/growl noise and beating my window with his tail. It's loud and obnoxious but I am more concerned that if he keeps knocking on it like that, he might fracture the window pane. Am I underestimating the toughness of glass and/or overestimating the strength of my cat's tail? It's the kind of knocking that someone might do to get your attention. For now I've closed the blinds but rolled them open and moved his tower from the window so he can't destroy the blinds trying to get on the sill. Am I just being paranoid? I hate to take away his source of entertainment during the day.

Nekkid Truth!

Maybe if the glass is very thin and old.. Otherwise, no


He won't be able to break the glass with his tail. If he ran and jumped at the window, he might, but it also depends on the window itself. Take your hand and smack the window. Glass holds up to things, its why we use it for windows in houses and in cars. I would move his cat tree back to the window. Like you say, its one of his sources of entertainment. A window is literally kitty tv. If anything, I would try and get the strays relocated. Talk with local animal control. They probably won't come and pick up a cat that isn't violent, but they should be able to loan you a live animal trap so you can trap the cat and bring it in to them.