Sorry, Bob. Dealing with mini dramas my end. I think I've missed a fair bit.
I know every tribe is different but that low purring sound is contentment with my lot. They are all @ the back door just now & someone gave an alert. It was loud & a trilling sort of scream. Miner bird! Miner bird!

They all went still & watched until it exited the yard. And they're harmless. Somewhere on my thread I have captured a little bit of it. It's often soft but can get super loud ~ especially if several hens join in.