If you can not manage an outside enclosure of any kind, then simply build a few window shelves so the cats can still see and hear the birds and insects outside. (wagbrag.com)
Window shelves also allow the cat to watch the great outdoors without being exposed to its dangers. (littlebigcat.com)
Every retailer should also stock beds and window shelves for the family feline, as well. (petbusiness.com)