Found a chicken acting strange this morning. She (or he) is a 2 1/2 month old Black Copper Marans. When I opened the door and all the other chickens rushed out to the yard as usual, she stayed behind on the roost. I puttered around filling water and such - she just sat there. When I was done I came to check on her - she was quiet but seemed to be making a strange small noise with every breath. I picked her up (she didn't shy away as she normally would) and set her outside by the food. She didn't eat, and when a bigger hen came up to eat, she crawled back in a corner under a ladder (all the littler chickens' favorite hiding place when the big girls are being mean) and sat there making the same sound - but once in a while she makes a louder noise and shakes her head. I'm attaching a video so you can see what I mean. I've never had a sick chicken before - Do you recognize the behavior? What is it? Do I try to treat it? (I am not somebody who will bring her in the house and baby her - if I can give her something that will help I will, but she needs to get well outside or be culled.)