Goodbye Dolly?

I hope not, but I'm afraid that Dolly might be gone. I fed all the squirrels, waiting for Dolly as usual, and they all showed up but for Dolly, who did not appear. I looked up at the cubby hole in her tree and saw a squirrel's tail hanging out. It was not moving. Could it be sleeping with its tail hanging out? I also noticed a bird sitting on a branch of the tree, and the bird would not fly away. It looked like some kind of bird of prey, not too large, about the size of a pigeon. But I could only make out its silhouette against the darkening sky. It would not leave, which seemed ominous. I'll go back tomorrow in hopes of seeing Dolly, but I just have a bad feeling. What could have happened? Could jealous squirrels have attacked her when I left her eating her cookie the other night? It seems unlikely.