New World (right) and Old World Vultures (left)
The New World and Old World vultures are a prime example of convergent evolution - despite being only distantly related, they ended up with many of the same traits, behaviors, and appearances, and occupy largely the same niches in their ecosystems.
These large birds all subsist largely on carrion (dead things) or carrion products (bones), soar long distances to locate food, flock when resting [Egyptian vulture aside], and have unfeathered or sparsely feathered heads and necks. They all provide critical “cleaning crew" and disease-reducing services in relation to humanity and other animals.
And all vultures, despite their ability to consume rabies and anthrax-ridden corpses without harm, are vulnerable to human destruction - even inadvertently.
With that out of the way, there are some fascinating differences between the two vulture orders!
Old World Vultures:
- Locate food by sight or hearing other scavengers locate a kill
- Excellent eyesight
- Build stick nests for eggs
- Frequently vocalize (and have a syrinx)
- Poor sense of smell
- Located in Europe, Africa, and Asia
New World Vultures
- Locate food by smell
- Will soar in circles above fresh kills or near-dead animals (who often give off a distinct scent) until other predators and scavengers leave
- Lay eggs directly on rocky outcroppings or in crooks of trees - no nests
- Practice urohidrosis to keep cool - they urinate onto their bare legs for the evaporative cooling it provides - very uncommon in birds
- No syrinx, only vocalizations are hisses and clicks
- Located in North and South America
Note that there are no vultures or condors in Australia or Oceania - the scavenger niche in those regions is filled by other birds, reptiles, and mammals.
Louis Agassiz Fuertes’ Album of Abyssinian Birds and Mammals. Field Museum of Chicago, 1930.
The Birds of America. John James Audubon, 1840.