How to keep car cover on with wind?

I have a 1999 Jaguar XJ8 and since my parking space is underneath a tree, I have to use a car cover to avoid bird poop. Seriously, if I don't have the cover on, I will have at least a dozen droppings within a day. Which is kind of funny.

But also a pain.

So, I have a car cover that I use, but when the wind picks up (I'm in Chicago), it lifts the cover right off the car.

I'd like to find a way to secure the cover that's fast and easy. I could always use bungees or something.

I figure somebody has also had this problem and solved it. Any suggestions?

Thanks!