I think the local stray cats in my neighborhood have decided that my backyard is "transit point" - much like Ellis Island was - on the way to good homes elsewhere.
About 18 months ago, a mama cat showed up in my backyard with three kittens. After much struggle and a $300 "donation" later, a local no-kill shelter took the kittens in and found them homes. I got mama cat spayed and she hangs out in my backyard. A few months later, another female cat showed up. Much struggle and $100 later, another no-kill shelter found her a home. Three months ago, a third female cat showed up. $150 later, found her a new home! Now there is a new male cat in my backyard!
I cannot help but wonder if the local strays somehow talk to each other telepathically!!