White-backed vulture
The white-backed vulture is an Old World vulture in the family Accipitridae, which also includes eagles, kites, buzzards and hawks. It is closely related to the European griffon vulture, G. fulvus. Sometimes it is called African white-backed vulture to distinguish it from the Oriental white-backed vulture — nowadays usually called white-rumped vulture — to which it was formerly believed to be closely related.
Description
The white-backed vulture is a typical vulture, with only down feathers on the head and neck, very broad wings and short tail feathers. It has a white neck ruff. The adult's whitish back contrasts with the otherwise dark plumage. Juveniles are largely dark. This is a medium-sized vulture; its body mass is, it is long and has a wingspan.Like other vultures it is a scavenger, feeding mostly from carcasses of animals which it finds by soaring over the savannah. It also takes scraps from human habitations. It often moves in flocks. It breeds in trees on the savannah of west and eastern and southern Africa, laying one egg. The population is mostly resident.
Status
As it is rarer than previously believed, its conservation status was reassessed from Least Concern to Near Threatened in the 2007 IUCN Red List. In 2012, it was further uplisted to Endangered. In October 2015, its status was changed to Critically Endangered because the ongoing decline is more severe than previously thought.The population size of the white-backed vulture has been decreasing significantly within the past few decades. In 1922, the population was estimated at 270,000. Over the past two decades, its population has noticeably decreased. While not much is known about the current population, a recent study found that white-backed vultures have a high survival rate. Individual adults have the highest survival rate, while 2 year old birds have the lowest survival rate. Across all ages, the survival rate is estimated to be 90.7%. This means that the deaths of adult vultures will lead to rapid population declines. The loss of adults will cause less reproduction and with younger birds less likely to survive, the population will drop drastically. A major cause of population decrease is the loss of habitat. Elephants have been endangering the vultures, since they destroy the trees the vultures live and nest in. Vultures tend not to nest in areas with high elephant populations. Fires have also caused the destruction of trees. Humans also have a large impact. Power lines have caused many vultures to be electrocuted. In Kenya especially, humans are using a toxic pesticide called Furadan, which has led to many vulture deaths. Vultures are also being poisoned by humans, although not intentionally. In order to kill hyenas, lions, and other predators, herders add poisons into their livestock. Vultures ingest the poison upon eating a deceased animal's carcass. This poisoning generally occurs outside of protected areas but is a leading factor in the population's decline. Habitats are also being disturbed by human land management and direct nesting persecution patterns.
More recent studies have indicated a new plausible factor in the current declination of the vultures. Researches have seen that there has been a rise in toxicity in the liver, kidneys, pectoral region, and internal organs. This toxicity is caused by higher levels of lead, cadmium, zinc, and copper. Although most of these metals level out as either non harmful or normal levels, the lead concentrate in the liver of the vultures and in the kidneys is higher than the average levels.
Studies have also been performed on the white-backed vulture and some species of Asian vultures within the Gyps clade to see the effect of veterinary diclofenac. Regardless of whether the vultures were given an oral or intravenous dose of the substance, the effects was nearly identical and the diclofenac eventually poisoned the subjects. This chemical is one of the greatest contaminants for the general vulture population because of its presence in livestock: easy food for the vultures.
Another study shows that there are heightened levels of polycyclic aromatic hydrocarbons, HPA's, which is not as likely a product in the endangerment resultant, but still concerning. HPA's, also known as polyaromatic hydrocarbons, are formations of hydrogen atoms surrounding rings of carbon. As common as these compounds are—found in foods, engines/incinerators, fires, combustion—there are many forms, and some carcinogenic. Although there is no direct correlation of the high levels of HPA's in the vultures, there is still a plausibility that it can result in a negative outcome for the species.
Another reason for the decline in the number of white-backed vultures is the decrease in the number of their nesting sites, which they construct in trees in savannah areas and which are roughly 1 meter in diameter. There is an inverse relationship between the amount of human activity and the amount of vulture nesting activity in said area, so as the amount of human activity in Africa expands, the number of nesting sites available decreases, putting the vultures at jeopardy.
On the 20th of June 2019, the corpses of 468 white-backed vultures, 17 white-headed vultures, 28 hooded vultures, 14 lappet-faced vultures and 10 cape vultures, altogether 537 vultures, besides 2 tawny eagles, were found in northern Botswana. It is suspected that they died after eating the corpses of 3 elephants that were poisoned by poachers, possibly to avoid detection by the birds, which help rangers to track poaching activity by circling above where there are dead animals. Most of them were new parents, leaving their young orphaned and "ill-equipped" for survival. Vultures are slow breeders, and losing over 400 on a week is a devastating blow for the species.
Diet
The primary food source of white-backed vultures are the carcasses of large, grazing animals found the wooded savannahs where it lives. This includes warthogs, zebras, gazelles, ostriches and even livestock. However, they can only eat animals with soft tissue, as their beak is not adapted for tearing through tough skin.White-backed vultures circle through the sky in search of freshly dead animals, often following other scavenger birds and mammalian carnivores to find it. Once a carcass is found, they will begin wheeling in the sky, signalling their discovery to other vultures. After feeding, white-backed vultures often rest with their wings spread and their backs facing the sun, as they have gorged themselves so much they can no longer fly.
Breeding
White-backed vultures nest in trees. They typically choose tall trees along riparian habitats and show strong a preference for Acacia species. The nests are large, around 1m in diameter, and are made of large sticks and lined with leaves and grasses. White-backed vultures face threats from habitat degradation and poaching; as such they have been shown to avoid anthropogenically-disturbed areas when selecting nest sites and protection status is also a strong determinant of site selection.White-backed vultures have a long breeding cycle. The incubation period is around 8 weeks and the nestling period is about 4–5 months.