After several rainy cold days the sun returned for two glorious fall days. After several hours cutting firewood, I treated myself to a nap on the newly cut hay field along the edge of the valley. I was looking up at the blue sky and the orange and red leaves above my head and feet, with an open horizon to the north and south.
I noticed a tiny speck appear in the north. As it came overhead I could see the typical shape of a soaring turkey vulture, its wings held above in a flat "V" shape. It was flying higher that I had ever seen and another speck followed, then another, all spaced out but headed in the same direction. Eventually I counted 25 over 5 minutes, with never more than 5 scattered in the visible sky at a time.
After 15 minutes my dog came over to tell me it was time to get back to work, but as I started to get up another speck came in sight. I checked the time and start counting again, ending with 53 when the parade ended 10 minutes later. Again, not a single wing flap the full time, and the vultures were always widely separated. There were never more than 5 birds visible in the whole open sky at one time.
Thermal updrafts allow turkey vultures much longer flights while soaring with their wings steady. The vultures migrate in the daytime and avoid rainy or cloudy days which don't have the updrafts that allow them to glide without flapping their wings. In the full time that I was watching them I never saw a single wing beat, just their steady glide and distinctive teeter from side to side as described in Bird Note.
Research on turkey vulture migration included a bird fitted with a heart-rate logger during 124 hours of flight during 38 contiguous days. That showed only a small increase in mean heart rate as distance traveled per day increased, which suggests that, unlike flapping, soaring flight does not lead to greatly increased metabolic costs.
I didn't get any pictures as I could never get more that two birds in a frame of my telephoto. It was just one of those "you had to be there" days.
