Suchergebnisse

Context
The increase in density of large tree species, Vachellia robusta and V. tortilis, in the Serengeti Ecosystem of Tanzania has resulted in a decline of small tree species Senegalia senegal, V. hockii, Commiphora spp. This change has occurred since the late 1970s, a consequence of an increase in wildebeest following the extirpation of rinderpest, which reduced the dry grass fuel for fires, resulting in low fire frequencies. Change in tree species raises the question of whether there are indirect consequences for the avifauna that depend on the large trees for food and nesting.

Aims
To determine how an increase in large mammals could influence diversity and distribution of avifauna communities in the Serengeti ecosystem woodlands.

Methods
Data used to estimate changes in density of large and small trees were measured by Point Centre Quarter (PCQ). Bird species were recorded in 19 small-tree sites and 18 large-tree sites in the Serengeti National Park. Richness of bird guilds was calculated in the two habitat complexes (small and large trees), and the 'rarefaction' method was used to assess the difference in richness in habitats of the study area. Mean abundance for each species was calculated over the total number of sites for each habitat and compared using the Wilcoxon Rank Sum test to examine how the abundance of avifauna changes with each habitat type.

Key results
There was an increase in the density of large trees in some areas in which they have replaced the original small trees. Such changes have resulted in greater richness of hole nesters and bark feeders, and a greater abundance of large-hole nesters and gleaner bird species.

Conclusions
Because the increase in tree density was caused by an increase in large mammals, we conclude that this increasing mammal population is indirectly increasing richness and abundance of birds using the trees.

Implications
Understanding the influence of large mammal populations on bird distributions has important conservation implications because the Serengeti ecosystem is classified as an important, endemic bird area.

Context
Differences in body size and mouth morphologies influence dietary resource separation among savanna ungulates, and this influences their distribution across landscape.

Aim
The aim was to understand the influence of body size and mouth morphology differences on both diet and patch selection by ungulate species in western Serengeti. Two hypotheses were tested: (1) for ungulate species, the relative body sizes and muzzle widths (mean muzzle width range: 3.1- 9.85) relate directly to food biomass, and to quality of diets selected in the wet season when food is abundant; (2) in the wet season, if food is not limiting, similar-sized species should exhibit greater dietary niche overlap than ungulate species that differ greatly in body size and muzzle width; moreover, similar-sized species exhibit less dietary niche overlap than ungulate species that differ greatly in body size.

Methods
In the western Serengeti ecosystem, road transects and direct observation were used to obtain data on the distribution and diet of five ungulate species namely buffalo, zebra, wildebeest, topi and impala; which have of varying sizes (range: 70–630kg) feeding in three different vegetation types. Grassland biomass, structure, nutrient content and ungulate use were measured at sites along transects.

Key Results
Results indicated that large-bodied ungulates utilised patches of greater food abundance compared with those of smaller ungulates. Body mass was also negatively correlated with diet quality, so that smaller animals ate higher protein and lower-fibre foods, as predicted. Diet niche overlap (niche similarity) showed a strong positive relationship with body mass differences among ungulate species, in support of the second of the two predictions from this hypothesis, namely that dissimilarly sized species could eat the same food.

Conclusion
Overall, the results suggest that in this savanna system, variation in ungulate body size influences resource separation even in the food-abundant wet season, and that this helps multiple species to co-exist.

Implications
Implementing more focused conservation strategies will improve wildlife habitat quality by integrating fire as a forage management tool with grazing preferences to promote forage heterogeneity in protected areas.

Vultures provide critical ecosystem services, yet populations of many species have collapsed worldwide. We present the first estimates of a 30-year Pan-African vulture decline, confirming that declines have occurred on a scale broadly comparable with those seen in Asia, where the ecological, economic, and human costs are already documented. Populations of eight species we assessed had declined by an average of 62%; seven had declined at a rate of 80% or more over three generations. Of these, at least six appear to qualify for uplisting to Critically Endangered. Africa's vultures are facing a range of specific threats, the most significant of which are poisoning and trade in traditional medicines, which together accounted for 90% of reported deaths. We recommend that national governments urgently enact and enforce legislation to strictly regulate the sale and use of pesticides and poisons, to eliminate the illegal trade in vulture body parts, as food or medicine, and to minimize mortality caused by power lines and wind turbines.

Vultures provide critical ecosystem services, yet populations of many species have collapsed worldwide. We present the first estimates of a 30-year Pan- African vulture decline, confirming that declines have occurred on a scale broadly comparable with those seen in Asia, where the ecological, economic, and human costs are already documented. Populations of eight species we assessed had declined by an average of 62%; seven had declined at a rate of 80% or more over three generations. Of these, at least six appear to qualify for uplisting to Critically Endangered. Africa's vultures are facing a range of specific threats, the most significant of which are poisoning and trade in traditional medicines, which together accounted for 90% of reported deaths. We recommend that national governments urgently enact and enforce legislation to strictly regulate the sale and use of pesticides and poisons, to eliminate the illegal trade in vulture body parts, as food or medicine, and to minimize mortality caused by power lines and wind turbines. ; Publisher PDF ; Peer reviewed

The texts presented here are extended and updated versions of the papers given at a session entitled "Archaeology and the global crisis - multiple impacts, possible solutions", held on the 17th September 2009 at the 15th annual meeting of the European Association of Archaeologists (EAA) in Riva del Garda, Italy. As coorganisers of this session, we were particularly happy to see that over a hundred colleagues attended and took part in some lively discussions, where sober realism was mixed with hope and determination. The session furthermore benefitted from the friendly atmosphere and excellent organisation of the EAA meeting itself, as skilfully orchestrated by Franco Nicolis together with Martina Dalla Riva, their teams and sponsors. Indeed the European Association of Archaeologists as a whole, so we feel, has amply fulfilled its vocation as meeting-ground and think-tank for professional archaeologists from Europe and beyond (http://www.e-a-a.org). We are grateful in any case that our session at Riva del Garda was sponsored – in an intellectual sense – by three EAA committees or working parties. One is the "Committee on archaeological legislation and organisation in Europe", chaired by Christopher Young and Jean-Paul Demoule: the crisis and the structural changes that follow make the critical and comparative work of this committee more important than ever before. Further support was received from the "Committee on professional associations in archaeology", chaired by Kenneth Aitchison, a committee that is acutely concerned with working practices in European archaeology and how they are being affected by the economic situation. The third and most recently created of these EAA groups is the working party on "ACE - Archaeology in contemporary Europe: professional practices and public outreach" (www.ace-archaeology. eu) – a European Commission 'Culture' programme funded network gathering a dozen of partners from across the continent to examine together the fields of practice and social dimensions of contemporary archaeology. In addition to the invaluable material support provided by the ACE network, many of its partners contributed their comments and insights to the preparation of the 'Crisis' session, and also through subsequent meetings in Thessaloniki (with our Aristotle University partner) and in Budapest (with our KÖH partner). In this volume, ACE partners have contributed the chapters on the situations in the Netherlands, Spain, France and Poland. Another relevant European initiative is the "Discovering the Archaeologists of Europe" project (www.discovering-archaeologists.eu), a review of the archaeological labour market in twelve European Union states with the support of the European Commission 'Leonardo da Vinci' programme in 2006-2008. As data for the project were collected in 2007, at the height of the economic cycle, they give us very valuable information and insights for critical comparisons with the ongoing crisis situation. ; European Commission (through the Culture 2007-2013 programme) in the framework of the ACE project – "Archaeology in Contemporary Europe. Professional Practices and Public Outreach" ; Peer reviewed