Some frames from a video I took to show just how many very large, dark birds there were flying above the quarry. I counted at least 40, completely silent. Not crows or ravens. I saw there were around 50 turkey vultures here this morning, so this is my best guess. But, some seemed to have white wing patches (not visible in the pictures unfortunately) which I haven't notice before. Maybe someone knows a bit more about them and could confirm.