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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Habitat selection and -preferences of White-fronted- and Bean Geese Anser albifrons, A-fabalis at the Lower Rhine - Historical changesand possible reasons
Auteurs :	Hauke Ballasus, Auteur
Type de document :	Article
Dans :	Vogelwarte (43(2) MAY 2005)
Article en page(s) :	123-131
Langues:	Allemand
Résumé :	This work investigates habitat selection and preferences of White-fronted- and Bean Geese wintering at the Lower Rhine area of North-Rhine-Westphalia (district Kleve), Germany. The study was made against the background of historical changes in the number of geese and their habitat selection respectively. The observations were based on 67 resp. 125 goose counts in the course of the winters of 1997/98 and 1998/99 within an area of 120 km(2). Habitat preferences were determined for the winter of 1998/99. The data shows: The proportion of White-fronted and Bean Geese within the study area was comparable to the one of the entire Lower Rhine. On average, 27.000 (1997/98) resp. 30.000 (1998/99) White-fronted- and 2.300 resp. 1.350 Bean Geese stayed in the area during the main resting periods. The winter maximum ranged between 51.000 resp. 57.000 White-fronted- and 7.000 resp. 5.000 Bean Geese. White-fronted Geese did not change their habitat selection. They made use of grassland to nearly 95%. Bean Geese were recorded to 60% (1998/99) resp. 75% (1997/98) on fields with sugar beet harvest remains. In the course of their main resting periods, Bean Geese made use of those remains to 55-90%. Their habitat selection was contrary to the one of the approx. four times larger goose stock of the earlier 1980s. Both species had the strongest preference for sugar beet remains, followed by periodical grassland. The preference of Bean Geese for the latter corresponded to the concentration of birds on that habitat within single units of the study area. After periodical grassland, white-fronted Geese preferred continuous grassland, Bean Geese, according to the respective winter, possibly maize stubble. The observed superficial change in habitat selection of Bean Geese was presumably a consequence of the reduced goose number, which has been supported by the utilization of grassland till the winter of 1987/88. The dramatic increase of White-fronted Geese in that winter seems to be the most important factor for the extensive removal of Bean Geese.

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