I've read on BYC several times about chickens purring and most people think it's what they do when they are content or happy. I heard my chickens purring and they all stopped and looked up into the sky. I looked up as well to see what the fuss is about (they've got me trained) and there was a hawk circling the yard. I have a coop and run that are both inclosed so there was no real danger to them. Anyway the purr sounded like a very low purr/growl. Seemed like they wanted to alert the rest of the flock but still be quiet as not to draw attention to themselves. Anyway, do you think the purr is more of a warning or a happy sound? I just added four new Cochins to my four I already had and I haven't heard this sound until I got them.