I introduced 3 new pullets to my existing flock of three a couple of days ago. Last night was the first night I let them all roost together, and all seemed to be okay. Rosita, the "top of the order" hen, and the only one remaining of the original small flock I started 2 years ago, was giving the new girls a few pecks to keep them in order when I went to close the coop, but everything seemed fine. This morning, she was lying on the ground under the roost, dead. My guess is she fell off, maybe in a squabble, but I didn't know that could happen. Any thoughts?