Bio: Norbert Schäffer is an academic researcher from Royal Society for the Protection of Birds. The author has contributed to research in topics: Acrocephalus & Population. The author has an hindex of 6, co-authored 6 publications receiving 178 citations.
01 Jan 1997
TL;DR: In this article, the authors reviewed the ecology of the Corncrake and found that the early mowing of hay and silage during the breeding season causes the destruction of nests and chicks.
Abstract: Declines in the population of the Corncrake have been reported from most states in the breeding range in Europe. States in eastern Europe with lower intensity of agriculture tend to have larger populations and higher population densities than states in western Europe. Information on the ecology of the Corncrake is reviewed. Corncrakes select tall vegetation that is not so dense that it is difficult for them to penetrate. Marshes and grasslands are important habitats, so drainage, conversion to other uses and agricultural intensification are threats to Corncrake populations. In most states many Corncrakes occupy grassland managed for the production of hay or silage. The nest is placed on the ground and the chicks are reared by the W in tall vegetation. W are capable of producing two broods of young in one summer, so the potential breeding season is long (May - August). Mowing hay and silage during the breeding season causes destruction of nests and chicks. The earlier that mowing occurs, the larger the negative impact on Corncrake breeding success. Agricultural development leading to earlier and more rapid harvesting of hay and silage is therefore another major threat to Corncrake populations in Europe.
TL;DR: In this article, a desk study was performed between May 1998 and October 2004, where information on known wintering grounds of the Globally Threatened Aquatic Warbler Acrocephalus paludicola was sought by means of questionnaires, personal communications, ringing data, publication and internet searches.
Abstract: Summary There is a clear need for protection of the migration and wintering grounds of the Globally Threatened Aquatic Warbler Acrocephalus paludicola, but little is known about them and the threats they face. To narrow this gap, a desk study was performed between May 1998 and October 2004. Information on known wintering grounds was sought by means of questionnaires, personal communications, ringing data, publication and internet searches. Results show that the Aquatic Warbler has so far been recorded in nine African countries, but with recent records since 1980 from only five countries (Egypt, Ghana, Mauritania, Morocco and Senegal). All present data suggest that the Aquatic Warbler migrates through north-west Africa in autumn and spring, with the wintering grounds limited to wetlands of western sub-Saharan Africa, with verified records only from Mauritania, Mali, Senegal and Ghana during the months of August to April. The species was almost always found in habitats similar to that of its breeding grounds, i.e. in Carex, Juncus or Phragmites (sedge, rush and reed) associations, but also in dense grasses, shrubs and other vegetation found in freshwater marshes, flooded or wet meadows, and along the edges of backwaters, flood basins, lagoons, lakes, ponds, rivers and wadis. Recent research suggests that at least some Aquatic Warblers may actually winter further south than the present data suggest, in countries such as The Gambia, Guinea-Bissau, Guinea, Sierra Leone, Liberia, Ivory Coast, Ghana, Togo and Benin, or maybe even in so far unexplored wetlands in Central or East Africa. Because wetlands throughout Africa face imminent threats from agricultural and tourist development, more fieldwork is urgently needed to further pinpoint the migration and wintering grounds of the Aquatic Warbler.
TL;DR: A novel approach to model the distribution of rarely recorded species, which is based on a combination of presence-only and presence‐absence modelling techniques, generates four progressively more conservative predictions of where the Aquatic Warbler overwinters in Africa.
Abstract: The Aquatic Warbler Acrocephalus paludicola is one of the most threatened Western Palearctic passerine species, classified as globally Vulnerable. With its breeding grounds relatively secure, a clear need remains for the monitoring and protection of the migration and wintering grounds of this rare and endangered migrant. Recent research has shown that the Aquatic Warbler migrates through northwest Africa in autumn and spring. The wintering grounds are apparently limited to wetlands of sub-Saharan West Africa, with records from only about 20 localities in Mauritania, Mali, Senegal and Ghana. Given the lack of knowledge of its whereabouts, we decided to use the available data to predict the wintering distribution of the Aquatic Warbler with the help of Geographic Information Systems (GIS). We used a novel approach to model the distribution of rarely recorded species, which is based on a combination of presence-only and presence‐absence modelling techniques. Using the program BIOMOD, we thus generated four progressively more conservative predictions of where the Aquatic Warbler overwinters in Africa. Whereas the most permissive model predicts the Aquatic Warbler to be found in a latitudinal band stretching from the Senegal river delta all the way to the Red Sea coast, the most restrictive model suggests a much smaller area concentrated within the regions around the Senegal river delta in northern Senegal and southern Mauritania and around the Niger inundation zone in southern Mali and eastern Burkina Faso. Such model predictions may be useful guidelines to focus further field research on the Aquatic Warbler. Given the excellent model predictions in this study, this novel technique may prove useful to model the distribution of other rare and endangered species, thus providing a means to guide future survey efforts.
01 Jan 2001
TL;DR: In this article, the Corncrake Crex crex overwinters in central and southern Africa, but migrates through and overwinter in the eastern parts of the world.
Abstract: Summary The Corncrake Crex crex breeds in the Palearctic but overwinters in central and southern Africa. While some information had previously been gathered about the Corncrake’s African wintering distribution, we here analyse a much more comprehensive database of 1,284 records based on a five-year desk study completed in January 2011 and use those records selected for spatiotemporal accuracy to build a continental distribution model. Our model was based mostly on climatic variables and predicts a high suitability for most eastern Africa countries south of the equator, but none of the western African countries with the exception of Angola and Namibia. Both the actual number of records as well as the distribution model thus indicates that the vast majority of Corncrakes migrate through and overwinter in the eastern parts of Africa. Because large parts of Angola, Mozambique, north-eastern Namibia, and Tanzania are predicted as suitable but have yielded very few actual records so far, they should be targeted for future field work. A very small number of Corncrakes may oversummer in Africa but such individuals are possibly unable to migrate due to sickness or injury, or may be first-year birds that are not ready to breed. An analysis of habitat and population density data indicates that, within the continental distribution, Corncrakes are mostly concentrated within grass-dominated habitats, mirroring their habitat preferences in the breeding areas. Corncrakes reach their wintering distribution mostly through an eastern migration route, but some individuals or subpopulations from the Western breeding population also use a western migration route. We also document the food choices, weights, and causes of injury and death within Africa. Because habitat conversion is accelerating all across Africa, we recommend constant monitoring of habitat availability and population densities within the Corncrake’s wintering distribution.
01 Jan 1977
TL;DR: This novel framework provides a baseline for adaptive conservation, management and monitoring of rare species at distinct spatial and temporal scales and highlights, from a statistically sound approach, the effects of multiple drivers in a same modelling framework and at two distinct scales.
TL;DR: Variation in annual survival and fledgling production per breeding attempt alone could not explain changes in abundance for at least seven species, and this may suggest that changes in post-fledging survival rates and/or the number of breeding attempts per year could have been important.
Abstract: Summary 1. Changes in agriculture have been linked to widespread declines in farmland bird populations. One approach to the identification of the causes of observed population changes is to investigate historical changes in national demographic rates. 2. We analysed the British Trust for Ornithology’s nest records database to investigate whether long-term farmland population trends could have been driven by changes in several components of the annual breeding performance of 12 granivorous bird species. Clutch size, brood size, chick : egg ratio and daily nest failure rates were analysed with respect to blocks of years during which abundance (as measured by the Common Birds Census) was increasing, stable or declining. The individual components of breeding performance were combined to provide estimates of the production of fledglings per breeding attempt. 3. Most species’ population declines were not associated with poor breeding performance per attempt. Effects of environmental change on this parameter therefore cannot be a general mechanism behind the major population declines seen. 4. A fall in linnet Carduelis cannabina fledgling production per attempt, driven primarily by increased nest failure rates during the egg period, represented the strongest evidence for an important effect of breeding performance on abundance. This change could have driven the principal population decline (1975–86) for this species. 5. Conversely, at least for the declining turtle dove Streptopelia turtur, skylark Alauda arvensis, tree sparrow Passer montanus, yellowhammer Emberiza citrinella and corn bunting Miliaria calandra, breeding performance per attempt was higher while populations declined. 6. Variation in annual survival and fledgling production per breeding attempt alone could not explain changes in abundance for at least seven species. This may suggest that changes in post-fledging survival rates and/or the number of breeding attempts per year could have been important. 7. Management to improve over-winter survival may be critical in reversing the population trends of most declining species, but such management might still best be directed at the breeding season. Post-fledging survival rates and the number of breeding attempts made within a season are little-studied demographic variables that are high priorities for future research and long-term monitoring.
TL;DR: A positive definition of species conservation on the basis of six attributes is elaborate and a categorization of different states of species Conservation is proposed using the extent of human management and the degree to which each of the attributes is conserved.
Abstract: The conservation of species is one of the foundations of conservation biology. Successful species conservation has often been defined as simply the avoidance of extinction. We argue that this focus, although important, amounts to practicing conservation at the “emergency room door,” and will never be a sufficient approach to conserving species. Instead, we elaborate a positive definition of species conservation on the basis of six attributes and propose a categorization of different states of species conservation using the extent of human management and the degree to which each of the attributes is conserved. These states can be used to develop a taxonomy of species “recovery” that acknowledges there are multiple stable points defined by ecological and social factors. “With this approach, we hope to contribute to a new, optimistic conservation biology that is not based on underambitious goals and that seeks to create the conditions under which Earth's biological systems can thrive.
TL;DR: Modelling the population growth rate showed that including the additional effect of mowing on female mortality resulted in a 1.7 times faster local population decline, consistent with the hypothesis that the extinction of whinchat populations in the lowlands of central Europe was caused not only by habitat degradation and low productivity, but also by increased man-made female mortality.