I'm in Minnesota so i don't think it could be buzzards, but I'll look up worf rats.
Today there was a huge, huge bird very close to the coops and chicken yard and it totally freaked out my flock. They were making a racket like I'd never heard and they were all trying to hide behind the coops, in a large kennel I have, etc. I turned around, saw the bird lift off from about 40 ft away and watched it fly into a small patch of woods nearby. It was bigger than a hawk but not the right coloring for a bald eagle. It was very dark, maybe black, on most of its body. The tail end was a lighter brown. The wing span was much bigger and different from a hawk.
Anyway, it made me wonder if that was the predator based on how close it was and how freaked out the chickens were. Also we determined that we lost 3 for sure, 2 were never found though. There was significant feather loss and based on colors I would think we lost 4, but then the numbers don't add up. So maybe one of my chickens was almost killed but escaped?
Would a bird of prey focus on the neck and crop/chest area of the chicken? I did think that the one bird we found had what looked like pecking damage in the crop area, because it was more like a circular area being focused on, rather than a full ripping/chewing style that I would imagine other animals would do. But I thought perhaps my own chickens had found her and canabalized her before we found her.