Vultures are primarily scavenger birds . They feed on the remains of dead animals that have been discarded by other predators. In the decomposition process, vultures play a fundamental role for the ecosystem.
Since the beginning of livestock, human beings have had a close relationship with vultures. The best way to dispose of dead cattle has always been to offer it to the vultures, also preventing possible diseases. Not without reason, in ancient Egypt, Nekhbet , with the head and wings of a vulture, was a protective goddess.
With the passage of time and the growth of human populations, ecosystems have been changing. Due to their dietary characteristics, vultures have to cover large territories by flying to sustain their populations, and the displacement or disappearance of other animals from part of their territory causes serious impacts. When large tracts of wilderness were converted to cattle pasture or farmland, and wildlife was forced to move, pressure on vultures increased, also fueled by hunting and removal of wild animals.
However, human beings continued to maintain livestock activity, which became a key element for some vulture populations. Open areas were established where the ranchers carried the remains, which served as a feeding area for the vultures: the middens .
The establishment of the middens became a tradition that both ranchers and vultures benefited from . Their behavior changed; the middens became a recurring source of food that was always in the same place. It also changed the diet, as well as the time and energy spent searching for food. Even the nesting and breeding areas were established closer to the middens.
When the availability of other types of food decreases, the middens help the survival of the vultures. The dependence of these animals changes according to the situation, the conditions and the species, both of animals left in the dunghill and of the vulture species. Some populations of the Egyptian vulture came to depend heavily on the middens for their food; on the contrary, the bearded vulture seems to use them rather little.
But not only vultures take advantage of these feeders: wolves, foxes, weasels, kites, seagulls, crows, crows, magpies, owls, buzzards and even storks and egrets are visitors to the middens, more or less frequently.
However, in Spain, the panorama changed drastically from the year 2000 . With the arrival of bovine spongiform encephalopathy, or ‘mad cow disease’, European health regulations prohibited abandoning dead cattle in the wild. Instead, it forced ranchers to transport the remains to disposal and incineration plants. The dunghills were no longer supplied.
This measure had an immediate effect of scarcity and loss of quality of the food available to the vultures, forcing them to change their territorial behavior . As a consequence, there was decreased reproductive success, reduced population growth, increased mortality even in young groups, and reduced egg quality in vultures.
Vultures, like many other animals, have adapted to human presence for thousands of years, and the provision of food in middens is now part of their heritage. This way of feeding the vultures is, in itself, a conservation tool for these species. They provide quality carrion to vultures, particularly useful when the population of wild prey falls, and thereby improve their reproductive success and the survival of their young.
In addition, middens can be converted into field laboratories for analyzes related to carrion and scavengers. Thanks to them, it has been possible to observe and study the behavior of vultures, the hierarchical relationship in their populations, the competition between different species of vulture or the selection of prey. Particularly valuable knowledge when establishing protection and conservation systems for these majestic animals, which are still necessary in ecosystems.
References:
Donázar, JA 1992. Dumpsters and garbage dumps in the biology and conservation of birds in Spain. Ardeola , 39(2), 29-40.
Grande, JM et al. 2009. Importance of middens in the conservation of the Egyptian vulture «Neophron percnopterus» in Spain. Munibe. Supplement, 29, 254-267.
Jha, K. et al. 2021. Brown World of Vultures: A Case of Vulture Restaurant .
Lagos, L. et al. 2015. EU Sanitary Regulation on Livestock Disposal: Implications for the Diet of Wolves. Environmental Management , 56(4), 890-902. DOI: 10.1007/s00267-015-0571-4
