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Résumé :
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Studies on the bird richness and abundance patterning in sandy coastal areas are almost neglected. A better knowledge of bird assemblage structure could permit the developing of appropriate conservation strategies in these key ecosystems. In this study, we aimed to test the hypothesis that a patchy. and structurally oversimplified ecosystem, as a Mediterranean sandy beach, may host bird assemblages highly variable in space and time and relatively poor in richness and abundance, whose structure should be therefore affected by chance. In 2007 a transect laid along a sandy beach was carried out, allowing to analyse the data temporally (six 2-month periods) and spatially (three longitudinal habitat types), either at single species or assemblage level. We observed a total of 25 bird species. Bird assemblages showed a taxonomical, phenological and ecological heterogeneity. In late autumn-winter the beach hosted the richest assemblage, in summer-autumn the lowest. Differences in mean values among 2-month periods were significant for species richness. Beaches represent patchy ecosystems with a different availability of resources in space and time. The presence of vegetation and linked trophic resources presumably permits the occurrence of a large variation in resource availability that determines a high turnover for different species along the temporal and spatial niche. Finally, we observed an inverse relationship between human presence and species richness.
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