D'OISEAUX NICHEURS D'UNE FORET ALLUVIALE DU RHIN (premiere partie)

摘要

Breeding birds of a Rhine riverine forest (part one).From 1992 to 1995, the breeding birds of a mature Oak-Elm riverine forest along the Rhine (Erstein Forest, Alsace, NE France- a nature reserve since 1989) were studied in order to identify the main characteristics of this insufficiently known forest type. Species richness is high (34) and breeding densities are high (129.3 pairs per 10 ha) as well as global diversify (SHANNON index of 4.13). These results are analysed then discussed in relation to other non-riverine conifer and broadleaved forests. Thisrichness can be explained by the architectural complexify of the studied forest resulting from the specific dynamics of riverside habitats: diversity of woody plant species, high vertical stratification, horizontal heterogeneity, abundance of large vines and vigour of plant growth are the most striking features of this habitat. Bird populations are similar to that of ordinary European Oak forest with three differences: a very high breeding density (50% higher), an abundance of shrubby habitats speciesin the heart of the forest, and the presence of species whose ecological optimum in Eastern France is cool montane habitat (Black Woodpecker, Dryocopus mortius, Firecrest Regulus atricapillus, Common Tree-creeper Certhia familiaris, Pied Flycatcher Ficedula hypoleuca). A comparison with the ancient Bialowieza forest has also been drawn: the higher temperatures and a much thicker and abundant woody vegetation explain the higher densities recorder in the Rhine riverine forest. Finally, a critical analysisof absolute population census tools is provided, highlighting weaknesses and suggesting possible alleys of improvement. In conclusion, we must unfortunately accept the fact that deep hydro-logical changes in European river habitats will modify the typical riverine forest architecture and will lead to the transformation of the Querco-Ulmetum minons into a yet unknown different type of forest.