In spite of what we learned from the old Western movies, when you see vultures circling it is usually an indication of rising air. Sunlight heats a rock outcrop, a clearing, or a parking lot. That heats the air, causing it to expand and rise. The Vultures use that as an "elevator", called a thermal, to carry them higher without flapping their wings. They will circle in the rising air until they are carried high enough to soar on to the next thermal.