Tag Archives: scavenging

Avian Scavengers

A number of birds will scavenge animal remains of all sorts. The most obvious are vultures but also several birds of prey including eagles, crows and even smaller birds such as roadrunners and Jays. This is an important ecological service to clean up what could otherwise be a source of disease. Actually some of the scavenging birds not specially adapted to the lifestyle can become ill from eating carrion.

Some scavenging birds, including our national symbol the bald eagle, are on occasion poisoned with lead bullet fragments in gut piles left over from field-dressed deer. A couple of lead fragments the size of a grain of rice can be lethal to an eagle.

The most commonly encountered scavengers are the Black and Turkey Vultures frequently seen cleaning up road-killed armadillos, possums, skunks, etc. They share some features and are distinct in others. They are both dark birds with bald heads. The lack of a feathered pate was thought to be for hygiene but recently its been suggested to be for thermoregulation. They also share incredibly acidic stomachs. The gastric juices of the Turkey Vulture are more acidic than a car battery and nearly one hundred times as acidic as our stomachs.

Vultures literally turn down their temperature at night by several degrees. In the morning they can be seen with their wings spread wide to the sun. Another method of temperature regulation involves urohidrosis, defecating down their legs in hot weather. This provides some cooling and may also be beneficial in the management of bacteria on their legs.

If approached by a predator or human for that matter they vomit. Some authors suggest this is a defensive action, as their vomitus is so acidic that it can cause burns. Other authors disagree, but all agree that the loss of the vomitus lightens the body weight to aid take-off for escape. Neither variety of vulture has a syrinx so they can only make grunting or hissing noises.

Black Vultures are slightly smaller than the Turkey Vulture. They have a poor sense of smell, therefore they detect a meal via keen eyesight. They will frequently soar higher than other vultures and follow them to a carcass. Black Vultures can show up in large numbers during the birth of livestock. Not only will they consume the afterbirth but also attack and kill newborn animals, and hence can constitute a serious agricultural pest.

Turkey Vultures are slightly larger and have a distinctive red head. Also, they have a somewhat brownish tinge to their feathers when viewed up close. They have the keenest sense of smell among birds. They tend to soar somewhat closer to the ground sniffing constantly for the odor of a carcass.

The importance of vultures was highlighted in India and Pakistan a decade ago. When the vulture population crashed due to the presence of a toxic (to vultures) arthritis drug in cattle carcasses, stray/feral dogs stepped up to fill the niche as scavengers. The dog population rapidly increased as did rabies. It caused a spike in human deaths due to rabies from dog bites.

Dr. Bob Allen, Ph.D., is Emeritus Professor of Chemistry at Arkansas Tech University.