Maybe one of these will not require divolging personal information. Note multiple locations where Black Vultures problematic. Chickens may not be ideal target for Black Vultures when compared to much larger and less mobile newborn calves...
My posting history on this forum solidly supports I am an advocate for wildlife. When engaged in politics, do your audience a favor and not stir confusion when pressing your point.
I have seen recent news articles concerning Black Vultures attacking live calves in Indiana and I think Oklahoma. A few years back there was a video showing a cow trying to drive Black Vultures away from her newborn calf. That video is not coming up in limited searches I ran last night.
Is it possible the Black Vulture is using your location as a roost where it is close to reliable thermals needed for soaring and can see other vultures from your location as well?