Vultures have been observed to hunch their bodies and tuck in their heads in the cold, and open their wings and stretch their necks in the heat. They also urinate on themselves as a means of cooling their bodies.[5]
A group of vultures in flight is called a "kettle", while the term "committee" refers to a group of vultures resting on the ground or in trees. A group of vultures that are feeding is termed a "wake".[6]
Early naturalists placed all vultures under one single biological group.Carl Linnaeus had assigned both Old World vultures and New World vultures in aVulturgenus, even including theharpy eagle. Soon anatomists split Old and New World vultures, with New World vultures being placed in a new suborder,Cathartae, later renamedCathartidae as per theRules of Nomenclature (fromGreek:carthartes, meaning "purifier")[8] by French ornithologistFrédéric de Lafresnaye.[9] The suborder was later recognised as a family, rather than a suborder.
In the late 20th century, some ornithologists argued that New World vultures are more closely related tostorks on the basis ofkaryotype,[10] morphological,[11] and behavioral[12] data. Thus some authorities placed them in theCiconiiformes family withstorks andherons; Sibley and Monroe (1990) even considered them a subfamily of the storks. This was criticized,[13][14] and an early DNA sequence study[15] was based on erroneous data and subsequently retracted.[16][17][18] There was then an attempt to raise the New World vultures to the rank of an independent order, Cathartiformes, not closely associated with either the birds of prey or the storks and herons.[19]
TheNew World vultures andcondors found in warm and temperate areas of theAmericas belong to the familyCathartidae. Recent DNA evidence suggests that they should be included within orderAccipitriformes along with birds of prey including hawks, eagles, and Old World vultures[citation needed]. Several species have a good sense of smell, unusual forraptors, and are able to smell dead animals from great heights, up to a mile away. The seven species are:
Black vultureCoragyps atratus in South America and north to the US
Turkey vultureCathartes aura throughout the Americas to southern Canada
Vultures arescavengers, meaning that they eat dead animals. Outside of the oceans, vultures are the only known obligate scavengers.[20] They rarely attack healthy animals, but may kill the wounded or sick. When a carcass has too thick a hide for its beak to open, it waits for a larger scavenger to eat first.[21] Vast numbers have been seen upon battlefields. They gorge themselves when prey is abundant, until theircrops bulge, and sit, sleepy or half torpid, to digest their food. These birds do not carry food to their young in their talons but disgorge it from their crops. The mountain-dwellingbearded vulture is the only vertebrate to specialize in eating bones; it carries bones to the nest for the young, and hunts some live prey.[22]
Vultures are of great value as scavengers, especially in hot regions. Vulturestomach acid is exceptionally corrosive (pH=1.0[22]), allowing them to safely digest putrid carcasses infected withbotulinum toxin,hog cholera bacteria, andanthrax bacteria that would be lethal to other scavengers[23] and remove these bacteria from the environment. New World vultures oftenvomit when threatened or approached. Contrary to some accounts, they do not "projectile vomit" on their attacker in defense, but to lighten their stomach load to ease take-off. The vomited meal residue may distract a predator, allowing the bird to escape.[24]
In various regions of Africa, the dynamic interplay of vultures and predators such as lions, cheetahs, hyenas, and jackals significantly influences the continent's food web. These avian scavengers actively engage in competition with these predatory animals for sustenance, meticulously tracking their hunting activities.[25]
Traditionally, vultures are known to bide their time, patiently observing from a distance or high in the sky as predators bring down their prey and commence feeding. Once these formidable predators have satiated their hunger and moved away from their kills, the vultures swoop in, making the most of the leftovers.
New research has revealed that these birds can, in addition to sight, respond to auditory cues indicative of potential foraging opportunities.[26]
Interaction between vultures and predators is not strictly sequential or one-sided. Vultures, being opportunistic creatures, will often engage in risky behavior if a prime opportunity arises. Sometimes, when the predator numbers are low or distracted, these large birds might move in earlier, attempting to snatch morsels from the kill before the predators have fully vacated the scene. This daring strategy, while high-risk, underscores the fierce competition and survival instincts prevalent in the harsh realities of the African wild.[27]
New World vultures also urinate straight down their legs; the uric acid kills bacteria accumulated from walking through carcasses, and also acts as evaporative cooling.[28]
Vultures in south Asia, mainly in India andNepal, have declined dramatically since the early 1990s.[29] It has been found that this decline was caused by residues of the drugdiclofenac in livestock carcasses.[30] The government of India has taken very late cognizance of this fact and has banned the drug for animals.[31] It may take decades for vultures to come back to their earlier population level, if ever. Without them to pick corpses clean, rabid dogs have multiplied, feeding on thecarrion, and age-old practices like thesky burials of theParsees are coming to an end, permanently reducing the supply of corpses.[32] The same problem is also seen inNepal where the government has taken some late steps to conserve the remaining vultures.
The vulture population is threatened across Africa and Eurasia. There are many human activities that threaten vultures such as poisoning and collisions with wind turbines.[33] In central Africa there have been efforts to conserve the remaining vultures and bring their population numbers back up. The decline is largely due to the trade in vulture meat, "it is estimated that more than 1×10^9 kg [2.2×10^9 lb] of wild animal meat is traded" and vultures take up a large percentage of this bushmeat due to the demand in the fetish market.[34] The substantial drop in vulture populations in the continent of Africa is also said to be the result of both intentional and unintentional poisoning, with one study finding it to be the cause of 61% of the vulture deaths recorded.[35]
A recent study in 2016, reported that "of the 22 vulture species, nine are critically endangered, three are endangered, four are near threatened, and six are least concern".[36]
The conservation status of vultures is of particular concern to humans. For example, the decline of vulture populations can lead to increased disease transmission and resource damage, through increased populations of diseasevector andpest animal populations that scavenge carcasses opportunistically. Vultures control these pests and disease vectors indirectly through competition for carcasses.[37]
Ancient Egyptians believed that all vultures were female and were spontaneously born from eggs without the intervention of a male, and therefore linked the birds to purity and motherhood, but also the eternal cycle of death and rebirth for their ability to transform the "death" they feed on – i.e. carrion and waste – into life.[43]
InPre-Columbian times, vultures were appreciated as extraordinary beings and had highiconographic status. They appear in manyMesoamerican myths, legends, andfables from civilizations such as theMaya andAztecs, some depicting them negatively, others positively.[44]
The Aztec vulture vessel at the new Pre-Columbian Mesoamerican Pottery Gallery
^Ward, J.; McCafferty, D.J.; Houston, D.C. & Ruxton, G.D. (2008). "Why do vultures have bald heads? The role of postural adjustment and bare skin areas in thermoregulation".Journal of Thermal Biology.33 (3):168–173.Bibcode:2008JTBio..33..168W.doi:10.1016/j.jtherbio.2008.01.002.
^Arad, Z. & Bernstein, M. H. (1988). "Temperature Regulation in Turkey Vultures".The Condor.90 (4):913–919.doi:10.2307/1368848.JSTOR1368848.
^Hamilton, S.L. (2014)."Sky Burials". In Galván, J. (ed.).They Do What? A Cultural Encyclopedia of Extraordinary and Exotic Customs from around the World. Santa Barbara, California: ABC-CLIO. p. 289.ISBN978-1-61069-342-4.
^Oaks, J. L.; Gilbert, Martin; Virani, M. Z.; Watson, R. T.; Meteyer, C. U.; Rideout, B. A.; Shivaprasad, H. L.; Ahmed, S.; Chaudhry, M. J. I.; Arshad, M.; Mahmood, S.; Ali, A. & Khan, A. A. (2004). "Diclofenac residues as the cause of vulture population decline in Pakistan".Nature.427 (6975):630–633.Bibcode:2004Natur.427..630O.doi:10.1038/nature02317.PMID14745453.S2CID16146840.
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