Actually, I thought it was gray squirrels with the bad reputation for nest invasion. They certainly get the blame for it in England!!! (Grays are native American animals, introduced to England not all that long ago!!)

Roseunhip; Do you know what a predator guard is? Two years ago when I purchased a wooden birdhouse it wouldn't go up in the trees unless it had an ample predator guard, made from hardware cloth with the edges snipped and sharp threads bent outward. Then attached around the entrance hole of the box. Guard sticks out about 6-7" in length. I didn't want raccoons or outdoor cats climbing the tree and reaching in with their dexterious paws/hands/claws. The predator guard was a little reassurance... Same thing w/squirrel nestboxes. The wildlife center has 'em built w/predator guards, wood piece on the inside of box w/2-3" lip, to deter tree-climbing carni-/omnivores from reaching in. I got the hardware cloth idea and sketch from a book.

Was in a pet-supply store on the 19th and a man came in to purchase bird seed. He despised the squirrels and admitted he'd take out his gun to shoot 'em if they dared interfere w/his seed offerings. :\ Oh yes, I know from wildlife conversations that reds are meaner, feisty, and horrendously territorial.

Please send a picture of your box after you've got it in place. I love seeing birdboxes in natural settings.

Some of the birdhouses and boxes they sell in catalogs and stores make me shake my head... dunno how any bird would feel safe, or homelike, in that creation?! And a note on nestbuilding materials; observed a gray squirrel tearing off chunks of corrugated cardboard from the sturdy carton (box from my foster rabbit housing) on our deck. Off she scurried w/the cardboard pieces in his mouth. Musta needa a new lining for his/her drey. Wish I had the camera at that second. ... We won't be so quick to put the box in the trash!

Greys are as bad or worse than reds for nestling predation. My understanding is that even chippies won't turn up their noses at meat now and again. You can buy predator guards commercially - they basically make the box entrance hole too long for anything to reach into. To protect against snakes, you need a baffle below the box.