Years ago before I built my house on my property, I stepped out of my cabin one morning and there was a raccoon stumbling around my truck and looking really sick. It was very skinny and starting to loose hair. It hissed a bit and moved off a few feet, but wandered around in circles and just looked lost. I assumed it was rabid and would soon die. I was running late for work, so I had to leave right away. That afternoon I came home and it was nowhere to be found. I went out looking, saw a group of buzzards circling, and found the remains in a gully, partially eaten by the buzzards.
I know buzzards are immune to lots of diseases and their digestive system allows them to eat diseased carrion. Just last week, I went out about sundown to move some water sprinklers on my yard and there was a buzzard standing near the sprinkler and drinking water on the grass. It didn't attempt to fly and just spread its wings and hissed at me. Even when I walked toward it, it just seemed to move away a few feet and continue hissing. I figured it would leave overnight, but the next morning it was still in our yard. My wife let our cats out before she knew it was still around. The cats approaced it, but when it hissed they backed off and just lay watching it. Since the kitties all have shots, we just hoped they would not attack the bird because it looked like it could do some pretty severe damage.
We were gone most of the day and returned to find the kitties had lost interest in the buzzard, but it was still around. My wife took the photos below. The first photo shows it spreading its wings and hissing at her. I really didn't want to shoot the bird in front of my granddaughter, so I waited until the next morning and it was gone. I've not seen it since, but my guess is it was sick and wandered off into the woods. I know buzzards are supposed to be immune to rabies, but this one acted very much like any other animal with rabies. Maybe it was just old, sick, and dying, but I didn't want to take any chances.