Wow, a 100% "yes" to letting this little kitten stay; I'm amazed. Today at roost time, it settled down next to the roost house and went to sleep. I walked past it several times & it didn't run away, but it watches me. Since we can't let the dog run the yard any more (since she killed so many young chickens), there's nothing to go after the rats, which are in abundance. I DID get it in a picture of the flock without realizing it was there. Thanks so much to everybody for your input.
I guess we'll abandon any thought of not latching down the roost door when chicks are big. Today, I found a possum in a bucket, with FIVE babies! It had thin wire wrapped all around it from getting tangled near our koi pond, couldn't get away, so it took refuge in a tub at daylight. Poor mama possum had struggled so much, the wire was cutting into its middle. We scooped them all into the trustworthy pet carrier, & I was able to snip the wire into pieces, staying away from those needle teeth. We took them all to a deeply wooded area AWAY from our house and let them go. Our chicks would be on the dollar menu with 6 possums in the yard at night! Baby possums are as cute as can be; we even raised 2 orphans, but never again. Possum relocation was the day's excitement today!