What a joy to publish a guest blog piece from a friend and true expert on bird behavior. The honor is even greater and more personal as Dr. Rylander was one of my principal professors when I attended college and majored in Zoology. What a surprise when Dr. Rylander and I learned that following our retirements that we had both chosen Fredericksburg, Texas, as a place to live. He is the author of Behavior of Texas Birds, published by the University of Texas Press.
One of the nearly constant sights over our ranch is the presence of vultures languidly circling high above. Little did I understand the differences of the two types of vultures that we see, although always being amazed by their graceful flight and efficient clean up of roadkill along our rural roads. Dr. Rylander makes their presence more meaningful and enjoyable to view than I had ever considered. Enjoy!
Guest Blog Piece by Kent Rylander, Ph.D.
Growing up on a farm during the late 1940’s, my brother and I called them “buzzards” – those large, black, hawk-like birds that soar in circles high overhead, or that stand on the highway by a road kill and fly away lazily if cars approach too closely. Even today most farmers in Denton County call them buzzards, and some still shoot them because they think they’re hawks or that they transmit diseases.
Later, when our parents gave us a field guide, we learned the preferred name, “vulture,” a term ornithologists introduced to distinguish our vultures from the unrelated African buzzards. We also learned that two species occur in Texas, the Turkey Vulture and the Black Vulture.
Overhead these two vultures might appear to be the same species because they are so similar in general appearance. However, a closer look reveals that the Turkey Vulture is very light on the wing and rocks gently back and forth as it effortlessly soars for hours; it rarely needs to flap its wings. In contrast, the Black Vulture’s body appears too heavy even for its broad wings. Indeed, Black Vultures must flap and glide just to stay aloft even at high altitudes where thermals are strong.
The “personalities” of these two species are related to their different body types. Both have keen eyesight and regularly search for carrion while they soar high above the ground, but they differ in an important way. The Turkey Vulture’s large wing to body ratio allows it to fly low over the ground and locate small animals such as snakes and rodents. It also has a sense of smell, which almost all birds, including the Black Vulture, lack because olfaction is useless for an animal that spends most of the time in the air.
More than a century ago Audubon claimed he demonstrated olfaction in Turkey Vultures by placing a dead animal under a sheet next to a realistic painting of a carcass. A vulture flew down to the painting but ignored it, then pulled the carcass out from under the sheet.
Although Black Vultures can’t locate small carcasses because they must fly high to stay aloft, they compensate for this limitation by watching Turkey Vultures forage low over the ground. When a Black Vulture sees a Turkey Vulture feeding on a small carcass, it drops down and drives the Turkey Vulture away. The Turkey Vulture seems to accept being bullied by its much heavier and stronger relative, even when both are at a large carcass.
Is the Black Vulture more aggressive because its size enables it to be a bully, or is it basically just a more aggressive animal?
The answer to this question lies with the young, fluffy white fledglings, which hatch and live in small caves in cliffs and rock formations. When a person approaches a Turkey Vulture fledgling, the young bird cowers and retreats to the back of the cave; but when a Black Vulture fledgling is approached, it hisses and lunges at the intruder.
So when we look up and see Turkey Vultures and Black Vultures soaring together, ostensibly cooperating while looking for a well-deserved meal to share, we know that, thanks to their genetics, they’re not foraging together because they’re friends.