Melman D.,Wageningen University |
Wymenga E.,Altenburg and Wymenga |
Bruinzeel L.,Altenburg and Wymenga |
Schotman A.,Wageningen University
Landschap | Year: 2012
The unfavourable conservation status of meadow birds in the Netherlands is of serious concern for authorities and conservation bodies. Since 1975 efforts have been directed towards conserving all meadow bird populations nationwide. This approach of spreading the efforts did not reverse the negative trend and at best the investments succeeded in slowing the decline. In order to achieve a turning point, the concept of designating core meadow bird areas has been launched. This idea follows directly from patterns observed in the field, in which meadow birds increasingly tend to concentrate in high quality areas. The core meadow bird approach, and the tools necessary to assign and maintain these, stresses that significant progress in conservation can only be achieved with increased efforts spread out over a smaller area. This approach follows partly from the fact that a considerable rise in budgets labelled for meadow bird conservation is currently not realistic. What can be expected of these meadow bird core areas? And what are the associated implications? This article focuses on the black-tailed godwit, the flagship species of the Dutch meadow bird community and a model species for which detailed ecological and demographic data is available. However, possible consequences for other species are touched upon in this paper. The core area approach may be applied to other species as a scientific base for nature conservation. A possible consequence of core areas is a change in involvement of and support by the public and agrarians, performing an important role in the current agri-environmental schemes.
Zwarts L.,Altenburg and Wymenga |
Bijlsma R.G.,Groningen Institute for Evolutionary Life science |
Van Der Kamp J.,Altenburg and Wymenga |
Sikkema M.,Altenburg and Wymenga |
Wymenga E.,Altenburg and Wymenga
Ardea | Year: 2015
In West Africa, tree preferences of wintering migratory birds (and African residents) were quantified in order to assess the importance of wintering conditions on distribution, abundance and trends of insectivorous woodland birds. This study encompassed 2000 plots between 10-18°N and 0-17°W, visited in October-March 2007-2015, and covered 183 woody species and 59 bird species. Canopy surface (measured in a horizontal plane) and birds present were determined in 308,000 trees and shrubs. Absolute bird density amounted to 13 birds/ha canopy, on average, varying for the different woody species between 0 and 130 birds/ha canopy. Birds were highly selective in their tree choice, with no insectivorous birds at all in 65% of the woody species. Bird density was four times higher in acacias and other thorny species than in non-thorny trees, and seven times higher in trees with leaves having a low crude fibre content than in trees with high crude fibre foliage. Salvadora persica shrubs, but only when carrying berries, were even more attractive. Overall, densities of migratory woodland birds were highest in the (thorny) trees of the Sahelian vegetation zone. This counterintuitive finding, with highest numbers of wintering birds in the driest and most desiccated parts of West Africa (short of the Sahara), also known as Moreau's Paradox, can be explained by the foliage palatability hypothesis. The Sahelian vegetation zone has always been subject to heavy grazing from large herbivores, and as a consequence woody species have evolved mechanical defences (thorns) to withstand grazing of large herbivores, at the expense of chemical defence against arthropods. South of the Sahel, with a much lower grazing pressure, thorny trees (rich in arthropods) are replaced by (usually non-thorny) trees with less palatable foliage and a higher crude fibre content, and hence with less arthropod food for insectivorous birds.