Biology Of Vultures
Although the vultures of the Cathartidae and Accipitridae have evolved from different ancestral stock, the two groups occupy broadly similar ecological niches. As a result, the vultures in these families are highly convergent in many aspects of their biology and ecology. All vultures have very broad wings with marginated primary feathers at the tips that allow them to soar at great heights and position themselves in thermals, thus flying for hours with little effort. This is a very useful ability for animals with excellent eyesight, because they can scan for carrion over great expanses of terrain. Once most vultures become airborne, it is unusual to see them flap their wings. In fact, most species are rather weak at active flying, and they sometimes appear to be straining their capabilities when they are taking flight from the ground.
All vultures have a hooked beak. The neck muscles and beak of vultures are too weak to tear the tough skin of recently dead, large animals, but they are able to deal with carcasses that have had some time to decompose. Until this happens, only the eyes of the dead animal, apparently a delicacy among vultures, can be eaten. Vultures have long, clawed toes, but their feet cannot grasp with much strength. Because of their relatively weak beaks and feet, these birds survive almost entirely by scavenging dead animals, and increasingly in many areas, the refuse of human towns and habitations.
Vultures rarely kill anything. They are rather timid when confronted by a living adult animal, even if the creature is obviously unwell, and therefore a potential meal. In such a situation, vultures will typically wait patiently nearby until the animal dies before they begin to eat. However, vultures have been known to attack relatively helpless, recently born, young animals.
Vultures are binge eaters of the first order. Their prey of dead animals is not always plentiful, and these birds sometimes must pass a rather long time between meals. However, when a large corpse is available, vultures will avail themselves of it to the fullest possible degree. Under such conditions, vultures can sometimes become so engorged with ingested carrion they are unable to fly. If they are disturbed when thus grounded, vultures must lighten their load so that they can become airborne. They do this by regurgitating their food, representing a case of reluctant avian bulimia.