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La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	La Reserve naturelle de la petite Camargue alsacienne, haut lieu du râle d’eau Rallus a. aquaticus en période de reproduction, dans la plaine du Rhin méridionale - Est de la France (2018)
Auteurs :	Benoît Wassmer, Auteur
Type de document :	Article
Dans :	Annales scientifiques de la Réserve de la Petite Camargue Alsacienne ( 2018)
Article en page(s) :	1-26
Langues:	Français
Mots-clés :	Rallus aquaticus ; Grand-Est ; Rhin ; Reproduction ; Dynamique population
Résumé :	Petite Camargue Alsacienne Nature Reserve, Water Rail top breeding area in the meridional part of the Rhine valley. Water Rail is one of the most poorly known species of the French avifauna. 30 years after the first census in the area, a new survey was conducted from autumn 2013 to summer 2014. Using playback (announcement call referred as «pig squealing»), about 40 % of the responses were duets in spring and summer (n = 179). Cumulative values for the four seasons were 46 % higher than the first time. A difference probably due to a better water level during the breeding period and survival rate after a mild winter. Site fidelity rate 2013-14 compared to 1990-91 was remarkable, reaching 64 and 61 % of inhabited areas in autumn and spring. During the four seasons, the distribution was uniform (0,752 ≤ GMASD ≤ 0,944). The NND (ind. or pairs) has varied significantly between autumn (116,6 ± 61,7 m) and spring (204,7 ± 99,8 m). The lowest density of 0,14 ind. / ha recorded in winter attests to the departure of some of the local birds, females essentially. A minimum of 13 breeding pairs were counted (Kirchenerkopf excluded) but the whole population was probably greater than 20 pairs (about 10% of the Alsatian population). So density was > 0,13 bp. / ha. a higher value having been obtained in the hearth of the area (1 bp. / ha). Water Rail occurred in heterogeneous wet habitat : 78 % of the pairs were established in mixed vegetation Phragmites, Carex and Salix bushes. Water depth was between 1-5 (15) cm. The major component was reed (89 %) than sedge (74 % – cover > 50 % within a 3 m radius observation–plot, n = 27). The laying period has been established from April 15th to August 9th. Observed in mid July, groups of non-flying youngs of different ages was a serious indication of two annual broods. In autumn, an influx of foreign birds could explain a real sensitivity to the intrusion (spontaneous vocalizations in response to the presence of the observer or response as soon as the playback begins). During this season, the sexe ratio was highly biased in favour of males (12,3 : 1). In Alsace, Water Rail is classified Vulnérable in the Red List. In a cross-border conservation strategy, to improve connectivity between small and highly isolated wetlands is of prime importance. Given the reduced extend of wet reedbeds (between 100 and 200 ha in Alsace), recognizing the rule of ecological managment of gravelpits and other waterbodies would be helpfull.

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