New World Vultures
The vultures of the Cathartidae have perforate nasal septums, which means that when one is looking at a sideways profile of the head of one of these birds, daylight can be clearly seen through their paired nostrils.
It appears that at least some of the American vultures have an excellent sense of smell, a very rare and unusual trait among birds. The turkey vulture (Cathartes aura), for example, has the largest olfactory system of any bird. There is also a great deal of behavioral evidence that a sense of smell is a significant aid to vultures in finding their food of dead animals. This ability is especially useful for vultures that find some of their fragrant food of carrion in relatively closed-canopied ecosystems, such as shrublands and forests.
Most species of vultures have a featherless, naked head. This is likely an adaptation that facilitates sanitation, because these birds often have to reach far into a decomposing carcass in order to feed. Most species with naked heads have brightly colored and patterned, warty skin on their neck and head, which is important in species recognition and in courting and aggressive interactions. The male Andean condor (Vultur gryphus) has a large, fleshy structure known as a caruncle on the top of its naked head, seemingly bizarre to humans, but undoubtedly most alluring to females of the species.
The courtship rituals of American vultures generally involve open-winged strutting on the ground, followed by impressive displays of aerial soaring and gliding. Vultures are monogamous, and both sexes brood the eggs and care for the young. Vulture chicks mature slowly, taking up to six months to leave the nest, in the case of the Andean condor.