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Résumé :
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Capsule Water Rail Rallus aquaticus and Moorhen Gallinula chloropus abundance is affected by habitat (both species), site isolation (Water Rail) and elevation (Moorhen). Aims To evaluate the effects of patch area, habitat, isolation, elevation and inter-specific interactions on the abundance of two under-studied species, Water Rail and Moorhen; i.e. a wetland specialist and a more generalist species, respectively. Methods We modelled species\' abundance at 28 sites in a wetland system in Trentino (Italy), using variables describing both habitat and spatial configuration of sites. We evaluated spatial autocorrelation and carried out an AIC(C)-based model ranking and averaging, whose results were cross-checked using hierarchical partitioning. Results Water Rail abundance was positively affected by cover of reed-bed and other wetland herbaceous vegetation, and negatively by the distance to the nearest wetland. Moorhen abundance was positively affected by cover of reed-bed and negatively by elevation and cover of woody vegetation. Conclusions Results matched the preference for reed-beds and other wetland herbaceous vegetation reported at the local scale for Water Rails, and highlighted a negative effect of spatial isolation. Our work further demonstrates how explanations of species occurrence and abundance in fragmented landscapes must consider variables describing both habitat quality and spatial configuration.
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