This is very unusual.. Usually my chickens are out in their run, jumping over one another at the door, waiting for me to open it up and they rush out into the yard en masse.. Today they don't even want to leave the coop. I finally shoo'd them out into the run and they all ran back into the coop. The only thing has has changed has been that I replaced their wood chip bedding with hay last night.. They seemed to really like it.. What is going on?? None seem ill, no evidence of predators trying to gain entry. I can't even blame a bad storm.. Is it the hay?