Ganzen in de Oostkustpolders: 45 jaar evolutie van aantallen en verspreiding
Kuijken, E.; Verscheure, C.; Meire, P. (2005). Ganzen in de Oostkustpolders: 45 jaar evolutie van aantallen en verspreiding. Natuur.Oriolus 71(Bijlage): 21-42
In: Natuur.Oriolus. Natuurpunt Antwerpen Noord: Turnhout. ISSN 1379-8863, more
Also appears in:Devos, K.; Leysen, K. (Ed.) (2005). Ganzen. Natuur.Oriolus, 71(Bijlage). Natuurpunt: Mechelen. 183 pp., more
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| Authors | | Top |
- Kuijken, E.
- Verscheure, C.
- Meire, P., more
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| Abstract |
The most important wintering location for wild geese in Flanders and Belgium is found in the Oostkustpolders (East coast polders) between Bruges, Ostend and Knokke. After their discovery in 1958 the geese have been intensively studied and the results of their long term monitoring is presented here. Primarily the two most important species dealt with here are White-fronted Goose Anser albifrons and Pink-footed Goose Anser brachyrynchus, with references to Bean Goose Anser fabalis rossicus, Greylag Goose Anser anser and Barnacle Goose Branta leucopsis. The trends in winter maxima as well as the total presence (expressed as goosedays) is discussed, also the phenology and related shifts. Concerning changes in preference for available habitats, the threatening reduction of historically permanent grassland in the polders means that geese are increasingly dependent upon farmland for foraging. The evolution of the maximum numbers of White-fronted and Pink-footed Geese over almost half a century is related to the strongly growing breeding populations of both species, coming from Northern Russia/Western Siberia and Spitzbergen respectively. At the same time the role of hard winters is emphasized which led geese to 'discover' this region. The decision following this for a general ban on hunting in 1981 has markedly influenced a number of be ha vi oral aspects, such as elimination of long distance travel to sleeping quarters, more efficient selection of habitat and use of terrain and above all the resulting spread of the grazing pressure over a large area. The marked temporal and spatial change is a phenomenon for which a number of characteristics and fundamentals are analysed: apart from the general increase in numbers, the shift in proportion between White-fronted and Pink-footed Geese is clearly to the advantage of the latter. Also the phenology (dates of arrival, winter peak, departure) and the influences of weather conditions on them show significant evolution. It is presumed that the general trend toward earlier dates might give an indication of climate change. The numbers of Greylag Goose and Barnacle Goose are also discussed. These have become worth recording only in the last 5 -10 seasons, but seem to have no influence on the self stabilizing trend of numbers, length of stay and goosedays of the wintering geese in the Oostkustpolders.The territorial expansion during 47 winters is coupled with sometimes clear differences in the preference of species for particular polder complexes, shown in particular by the Pink-footed Goose expansion westwards. Whether this is to do with competition between them is unclear. Grasslands remain on average 75 - 95% of the terrain used for foraging. During the course of the investigation, the distribution of the geese evolved from 'rotational grazing' to the 'overspill model' with 'local seeding' and currently a 'simultaneous expansion strategy'. Much attention has thus been given to such parameters as number of goosedays, length of stay, surface area used and the resulting grazing pressure. The ability of areas to support this will depend to a large extent on the conservation and/or restoration of polder grasslands. The concern about disappearing grassland areas and the capacity to support of the Oostkustpolders is at the heart of measures and the capacity to support of the Oostkustpolders. These must offer a guarantee that this region can sustain its internationally recognised function as the most southerly wintering location for the Pink-footed Goose. |
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