Cats and windows go together. A cat’s hunting instincts cause them to always be on the lookout for something to hunt–watching outside for some kind of movements–something to keep them from being bored inside and stimulate their minds. My catio has taken things a bit further. Indeed cleaning it out I have found dead birds and small mouse carcasses inside–the large fence wire I used allowing them easy access if they dared. I have on the rare occasion had a live bird fly through and fly around in the house! The catio is a large improvement on the window, but there is not free reign to go out. Weather is a factor and someone must be at home to have it open; therefore, the window is the good old standby always available.