My black and white Sussex started acting funny this afternoon. She's standing but her beak is lowered to the ground and she bobbles slightly like she's drunk. It's as if she can't lift her head even though she seems to be trying. I found her like this in the run just before dusk and she managed to get herself in the coop with the others. We have since brought her in the house to quarantine. She doesn't seem to be eating, drinking, or pooping. Even at 8:00 at night, when she should be asleep, she is standing and has her beak to the ground. What is this??