Coyotes and other carrion eaters are funny critters. Sometimes the possums are first to a carcass. They usually go in the rear of a hog. Then the coyotes show up to finish the job.
Some carcasses lay there mostly undisturbed by critters. i've seen this several times on the wheatfields in Tillman county, OK.
Most of the buzzards left SW OK last fall. They will be back in the spring.