This summer I was fortunate enough to see a California Condor on the north rim of the Grand Canyon. This was the fifth species of New World Vulture that I've seen, leaving two still to add to my list.
You don't hear much about the beauty and majesty of vultures which I think is a bit of a shame. They are spectacular soarers, really wonderful to watch as they ride thermals and move over the landscape without a single wingbeat. Here in North America we have three of the seven species, I'll introduce the entire cast below. I'll also discuss the Old World Vultures and their relationships to each other and the vultures we are used to seeing here in North America
The vulture familiar to almost everyone is the turkey vulture. In a diary four years ago lineatus did an excellent job of introducing this bird. I'll just mention that it is among the widest ranging birds in the new world occurring from southern Canada to Tierra del Fuego. It is, as far as I know, the only vulture that is migratory although it is only migratory in colder areas. It is also famous for its excellent sense of smell, a somewhat unusual trait amongst birds. The large nostrils are clearly apparent if you see the bird close up.
The other widespread vulture in North America is the black vulture. It occurs broadly in the southeastern, southcentral US ranging as far north as southern Illinois and extreme southern New England. Like the turkey vulture it ranges broadly through tropical America but doesn't quite get down the tip of South America.
Where I live now I have the opportunity to see both birds regularly. There are several clear differences in their habits. I see black vultures much less often than turkey vultures but when I do see black vultures I usually see a bunch of them. Black vultures seem to be much more social. I've read that they watch for other vultures descending to carrion rather than searching for it themselves which would explain why I see them flying less frequently. Black vultures are also more easily acclimated to human beings. In latin America they frequently live around towns and they are more reluctant to leave road kill than turkey vultures.
Both species appear to thrive in human modified landscapes and have expanded their ranges north over time. Unfortunately other vultures do not do so well in the presence of people as we shall see below.
Much rarer although perhaps at least as famous are the two condor species. These enormous vultures are among the largest birds capable of flight. Both species are restricted to mountainous regions. The plight of the California Condor and its near extinction and re-introduction are well known. The Andean Condor has a much broader range occurring, at least historically, throughout the entire Andean mountain range except perhaps for the far north. The bird is now very rare in the northern Andes but still persists in numbers in the wilder areas of the southern Andes
The Greater and Lesser Yellow-headed vultures are both closely related to and very similar in appearance to the turkey vulture. The primary difference is that the skin on their heads is yellow rather than red. Bet you didn't see that coming! Each is a habitat specialist: the Lesser occurring in grasslands and wetlands and the Greater occurring in the tropical wet forests of the Amazon.
Last is the King Vulture. This is probably the most unique of the new world vultures. Their plumage is mostly white, rather than dark. They have incredible, bizarrely ornamented heads. The species is widespread in tropical America, occurring where ever there are tropical forests. They will enter open country but only if forest is close by. The king vulture is larger than the other new world vultures except for the Condors.
Records of the King Vulture in Florida exist from the 1700s and it continues to be shown in Peterson's eastern field guide. Clearly the bird does not live in Florida now and the nearest location where it does live is the Yucatan peninsula.
What's with the 'New World' Vultures? It turns out that there are two (really three, I'll get to that shortly) distinct groups of birds called vultures. The new world vultures are a family, Cathartidae whose relationships to other birds are uncertain enough that they have now been given their own order: Cathartiformes. The old world vultures are all members of the family Accitripidae, indicating their close relationship to eagles, hawks, and kites.
So vultures are an example of what is one of the coolest (IMHO) phenomena in nature: convergent evolution. Two different groups evolve similar structures and behavior in response to the same environmental factors. Both groups of vultures are large, long-winged birds that make extensive use of soaring to remain aloft for prolonged periods looking for carrion. They (mostly) have featherless heads that are often brightly colored. Plumage is mostly dark with some patches of white or pale grey.
This leads to a nice story - separate groups evolve the 'vulture' appearance and way of life in the old and new worlds. However nice stories can be wrong or at least incomplete. There are a couple of extra wrinkles.
1) Old world vultures formerly existed in the new world and new world vultures formerly existed in the old world. Fossils of new world vultures have been found in Europe and extensive fossils of old world vultures have been found in North America. The European new world vulture fossils are quite old (circa 20 million years ago). In contrast some of the North American fossils of old world vultures are quite recent, dating to about 10,000 years ago. This is the same time period that saw the extinction of many large new world mammals.
2) Old world vultures themselves appear to consist of two completely different groups that evolved independently within the Hawk/Eagle family Acciptridae. The smaller of these two groups contains three somewhat unusual species: the Palm Nut Vulture, the Egyptian Vulture, and the Lammergeier. These birds are thought to be related to a group of tropical old world hawks known as bazas and honey buzzards. All three species are very different from one another. They do have more feathering on the head than other vultures.
The Lammergeier and its relatives The three species in the subfamily Gypaetinae are all very ecologically different from one another and two of them are real odd balls from a general vulture point of view. These birds have bare faces but the back and top of the head are fully feathered.
The Lammergeier is a very large vulture, also known as the bearded vulture. It is widespread in mountainous regions of Africa and Eurasia although it occurs in very small numbers everywhere except Ethiopia. It is a specialist on eating the bones of large mammals. When it finds bone it picks them up and drops them from a great height, cracking them to feed on the marrow within.
The Palm Nut Vulture is the smallest vulture in the old world. It is found broadly throughout subsaharan Africa and, as its name indicates, feeds mainly on the fruit of oil palm. It is one of the few old world vultures that remains abundant and is not declining.
The last species is the Egyptian Vulture which has a more typical vulture lifestyle. It largely occurs in northern Africa, southern Europe and from SW Asia over to India. Like many of the other Old World Vultures this species is declining across its range.
Typical Old World Vultures The subfamily Aegyptiinae includes the stereotypical vultures of the nature shows of my youth, feeding on animals killed by lions after the jackals and hyaenas were done. This is the largest group of vultures (13 species) and they are closely related. With the notable exception of the Hooded Vulture they are all very large birds. There is some ecological variation among the larger species with some having more powerful beaks, others having longer necks and so on. The video below shows four species feeding on a zebra carcass in Tanzania.
The greatest diversity of these vultures is in Africa but they also occur in southern Europe and across southern Asia to the Himalayas. Northerly populations are migratory in some species.
Decline of the vultures With a few exceptions, such as our own Turkey and Black Vultures most species world wide have had their populations decline over the 20th and early 21st centuries. There are a number of common themes to the declines of different species. Human persecution is one but most important is probably the decline in quality food sources. Vultures need dead animals to eat and a fairly substantial biomass of dead animals to sustain healthy populations. In many parts of the world vultures have had to shift from native mammals to domestic mammals as their main source of food. Unfortunately cultural shifts in cattle farming, including use of antibiotics and of simply no longer leaving dead animals where they died has reduced the food source for many vultures and even the carcasses that are available are tainted with antibiotics or deliberate poisons (left for jackals or coyotes not vultures).
The decline of the 'Old World' Vultures here in North America may be related to the loss of many large mammal species in a large scale extinction event following the last ice age.
Our own thriving vulture species appear to be benefiting from road kill. They are small species that commonly feed on animals like raccoons and armadillo that are frequently hit and killed by cars. In our case we may be increasing their food supply.