We have both reds and greys round here. The proportion varies according to how many greys our local squirrel trapper has managed to catch. She has several traps set up in the woods nearby. I regularly see both on the drive in front of the house. A hospital for injured grey squirrels is like a hospital for injured rats. Here's a red sitting on my windowsill. They come to eat the bird food.

A bit like controlling rabbits on your land