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Scavenging birds and ecosystem services
Chair General Ecology, Brandenburg Technical University Abstract: Scavengers play an important role in ecosystems. Their obvious service for public health is well
known at least in developing countries: In terms of ecosystem services they remove rotten meat and bones and
in doing so prevent serious diseases in people and livestock. Vulture decline and its negative effect on econ-
omy, public health and culture has well been studied in the case of India. One major effect was that rabies
spread as carrion was no longer consumed by birds but by mammals. So there is good evidence on the im-
portance of vultures as scavengers. However, vultures are mainly extinct in industrial countries like Germany
or China after prosecution and lack of food. Extinction of vultures occurred at least 200 years ago. Rabies was
a major risk to public health in Germany until the disease was eradicated by vaccinating foxes. Without com-
petition by vultures and without rabies causing death among foxes, their population increased tremendously
and foxes are now regarded as a threat for ground breeding birds. Whereas Germany interferes in the carrion
food web again by vaccinating foxes and causing more negative effect, India sees to eradicate the reasons for
vulture decline such as banning the use of Diclophenac in animal husbandry.In the NECROS project of BTU
Cottbus (Germany) the fragmented remaining food web based on carcasses is studied. Road kills of game,
mainly roe deer and wild boar, are deposited in a nature reserve to carry out field experiments. Carcasses are
monitored by automatic cameras. One of the main research aims is to find out what happens to the carrion
food web with only some vertebrate scavengers around and no vultures at all. Results show that compared to
complete ecosystems with large predators and vultures, the rudimentary food web based on carrion in Germa-
ny cannot provide the desirable ecosystem services.
Keywords: ecosystem services; scavenging birds; carcasses; vultures

1. Introduction
1.2. Scavengers in ecosystem service
1.1. Ecosystem service
There are numerous sources of mortality which cause nonpredatory death: death due to old age, malnutrition, Ecosystem services are natural processes that benefit disease, parasites, accidents, exposure, and catastrophic humans. The United Nations Millennium Ecosystem events; collisions with human-built structures, collisions Assessment distinguishes four principal types of ecosys- with automobiles, poisoning, and pollution (WHELAN et al. 2008). If sufficient scavengers exist, nonpredatory carcasses will be consumed. But if large obligatory scav- Provisioning services, such as production of fi- engers are absent, carcasses will not be consumed as quick as possible with bacteria dominating the process of Regulating services, obtained through ecosystem processes that regulate climate, water, and hu-man disease; Among vertebrate scavengers, vultures are essentially Cultural services, such as spiritual enrichment, obligate scavengers which are significant spiritually, cognitive development, reflection, recreation, economically and environmentally. They have historical-ly played a very important role in environmental health, by disposing of animal and human remains (PAIN et al. Supporting services, which include all other eco- 2003, GREEN et al. 2004, MARKANDYA et al. 2008). system processes, such as soil formation, nutrient Compared to other scavengers, vultures have high mobil- cycling, provisioning of habitat, and production ity, the flight maximize rapid carrion detection. They can Birds play many roles in ecosystem, such as predators, pollinators, scavengers, seed dispersers, seed predators and ecosystem engineers (WHELAN et al. 2008). Birds In India and elsewhere vultures have important role in take part in all the four kinds of ecosystem service. culture and religious significance (PAIN et al. 2003). For thousands of years and in different parts of world, hu- mans have laid out their dead for consumption by scav- the area is closed to the public due to contamination by engers. By consuming the dead person, birds literally ammunition, so disturbances by passersby are expected take the soul of the deceased to heaven. to be few; large vertebrate scavengers such as Wild Boar (Sus scrofa), Wolf (Canis lupus), White Tailed Eagle 1.3. Vulture declines in India
(Haliaeetus albicilla), Red Kite (Milvus milvus), Ravens Vultures help to dispose cattle carcasses in areas (Corvus corax) and others are known to be present. Ex- where beef eating is forbidden (RODRIGUEZ & periments were performed in all seasons from November BEARD 2005). The acidic condition in the stomach of 2008 till October 2011. We experimentally laid out road Gyps Vultures can kill many pathogenic bacteria, such as kills of game, mainly Roe Deer (Capreolus capreolus) anthrax, and reduce the risk of disease spread (PAIN et and Wild Boar (Sus scrofa) as most common game spe- al. 2003). They also help the Parsees to remove human cies. Carcasses are monitored by three automatic cameras corpses from traditional sites of “laying to rest” with two of them taking pictures and one taking videos. (RODRIGUEZ & BEARD 2005), which are called “tow- However, there was a sudden and drastic decline of 3. Results
vulture population in India. The use of the drug diclofenac in livestock was the cause of that decline We found several influences having impact on the (GREEN et al. 2004, SWAN et al. 2006). Livestock was decomposition and consumption of carcasses: the main diet of vultures in India (RODRIGUEZ & BEARD 2005). Diclofenac is a common drug against Season: In summer, carcasses are mainly con-sumed by arthropods and bacteria. Only Red Fox pain and inflammation (KRAWCZYNSKI & WAGNER 2008). Although healthy for mammals, it or its (Vulpes vulpes) is regularly eating from rotting metabolistic remains are poisonous for vultures (GREEN carcasses, while in winter consumption is done mainly by vertebrates. Wild Boar (Sus scrofa), Wolf (Canis lupus), Pine Marten (Martes Yet, carcasses of cattle are still transported to areas martes), Domestic Cat (Felis catus) and Raccoon on the edge of towns and villages. As there is no longer Dog (Nyctereutes procyonoides) used carcasses domination of vultures at carcasses, feral dogs, foxes and only in winter, especially after snowfall. In win- rats get access to food otherwise consumed by vultures. ter there are large flocks of Raven (Corvus This leads to growing populations of scavenging mam- corax) at the carcass, in summer only the resident mals which are in contrast to vultures carrying and spreading rabies. The risk for people and livestock of being infected with rabies has dramatically heightened. Condition of carcass: It makes a significant dif- Some areas are now increasingly dangerous to visit ference if the road kill shows open wounds or if (RODRIGUEZ & BEARD 2005). Declines of vulture the animal died of inside injuries. With no open populations have an ecological impact and present risks wounds even White Tailed Eagle (Haliaeetus to health, social systems and local economies (PAIN et albicilla) with its strong beak has difficulties in al. 2003). In most industrial countries such as Germany opening a carcass, and trying to open it is time or China, vultures are extinct. Extinction happened in consuming. In combination with the season, the Central Europe at least 200 years ago (BAUER et al. carcass starts rotting fast in summer and will not 2005) and decline was not rapidly like in the case of In- be used by most vertebrates. We have evidence dia but took place slowly by hunting, poisoning and lack for just one case when Ravens Corvus corax) of food. Ecosystem services carried out by vultures have were able to open the softer skin of a Wild Boar’s (Sus scrofa) belly and feed on the intes- In NECROS project of Brandenburg Technical Uni- versity, the fragmented remains of the food web based on carcasses are studied. What will happen to carcasses of (Vulpes vulpes) will eat of any carcass, the pup- large animals under such conditions? How long will it pies are mainly feeding on the large insects near take to decompose carcasses under different conditions? Can other scavengers provide the same ecosystem ser- Feeding strategy: Ravens (Corvus corax) do not actually feed at the carcass. They fill their craw with meat, hide it away and come back for more meat. As we often find more than 20 Ravens 2. Methods
(Corvus corax) at the same carcass, consumption rate can be accelerated much by Ravens (Corvus Study site is part of one of the largest former military training sites in Brandenburg, Germany. The area select-ed offers some advantages not found elsewhere: Most of Competition: Interspecific and intraspecific Consequences of the loss of these services cover competition is more complicated than expected. more than just lack of food for scavenging animals. It Although adult White Tailed Eagles (Haliaeetus seems plausible, that following the decline of vulture albicilla) dominate young ones at the carcasses, populations in Central Europe, populations of scavenging in groups of Raven (Corvus corax) there will be mammals increased as happened in India some years ago. one to mob any eagle by pulling their feathers on At least the threat of rabies was considerable until it could be eradicated by vaccination of foxes with drug the wings or tail. This strategy fails when used prepared baits. However, with no rabies to kill the grow- on Buzzards (Buteo buteo) as the Buzzard ing population of foxes, their numbers increased even (Buteo buteo) will strike back and single Ravens more. Foxes are now a common sight even in city centers get mobbed themselves by Red Kites (Milvus of large towns. In rural areas, foxes have become a seri- milvus) stealing the Raven’s meat stored in a ous threat to ground breeding birds such as lapwings. hideaway. Competition between vertebrates and bacteria is also remarkable; it seems to follow References
4. Discussion
[1] BAUER, H.-G., BEZZEL, E. & FIEDLER, W. (2005): Das When looking at the results it becomes obvious that Nonpasseriformes – Nichtsperlingsvögel. AULA: 1 – 808. Ravens (Corvus corax) play a large role in carcass ecolo- [2] GREEN, R.E., NEWTON, I., SHULTZ, S., CUNNINGHAM, gy. However, even large numbers of Ravens (Corvus Diclofenac-poisoning as a cause of vulture population declines corax) cannot contribute to the ecosystem services oth- across the Indian subcontinent. J. Appl. Ecol. 41, 793-800. erwise provided by vultures. Ravens (Corvus corax) can [3] KRAWCZYNSKI, R. & WAGNER, H.-G. (2008): Leben im consume carcasses quickly until only bones and skin Tod – Tierkadaver als Schlüsselelemente in Ökosystemen. – remains, which resembles the effectiveness of vultures. Naturschutz & Landschaftsplanung 40 (9): 261-264. [4] PAIN, D.J., CUNNINGHAM, A.A., DONALD, P.F., T.,PARRYJONES, J., POOLE, C., PRAKASH, V., ROUND, P., TIMMINS, R. (2003): Causes and effects of temporospatial Number of Raven must be sufficiently high. As Ravens congregate in large flocks only in winter, [5] RODRIGUEZ, J.P., BEARD, T.D., AGARD, J.R.B., they fail to provide vulture’s ecosystem services BENNETT,E., CORK, S., CUMMING, G.,DEANE, D., DOBSON, A.P., LODGE, D.M., MUTALE, M., NELSON, G.C., PETERSON, Carcasses must have open wounds so that Ra- PINGALI, P.L., BENNETT, M.E., ZUREK, M.B.(2005): vens can get access to the meat. Large predators such as Wolf (Canis lupus), Lynx (Lynx lynx) or Ecosystems and Human well-being: scenarios, volume 2 (2005). Bear (Ursus arctos) leave their kills with open [6] MARKANDYA, A., TAYLOR, T., LONGO, A., MURTY, wounds. Game that dies of another cause like old M.N., MURTY, S., DHAVALA, K. (2008): Counting the cost of vulture decline-An appraisal of the human kealth and other age, disease or parasites does not have open wounds. So the presence of large predators is http://www.scribd.com/doc/49834172/Counting-the-cost-of- vulture-decline%E2%80%94An-appraisal-of-the-human-health-and-other-benefits-of-vultures-in-India). [7] SWAN, G. E., CUTHBERT, R., QUEVEDO, M., GREEN, R. E., In Germany, there are only few areas that match these PAIN, D. J., BARTELS, P., CUNNINGHAM, A. A., DUNCAN, prerequisites. Such areas are Lusatia with Ravens N., MEHARG, A. A., OAKS, J. L., PARRY-JONES, J., SHULTZ, S., TAGGART, M. A., VERDOORN, G. & (Corvus corax) and Wolfs (Canis lupus) or the Harz WOLTER, K. (2006): Toxicity of diclofenac to Gyps vultures. Mountains same as Black Forest and Ore Mountains with Ravens (Corvus corax) and Lynxes (Lynx lynx). And [8] WHELAN, C.J., WENNY, D.G., MARQUIS, R.J.(2008): even there, large flocks of Raven will only be found in Ecosystem services provided by birds. (Available at winter. So ecosystem services which are similar to those http://onlinelibrary.wiley.com/doi/10.1196/annals.1439.003/abstr provided by vultures will be found only in small areas

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