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Résumé :
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This study addresses the development of a new set of indicators of bird populations using Relative Habitat Use (RHU), an objective method for indicator species selection. RHU facilitates the calculation of indicators for all nine basic habitat types included in the Danish Common Bird Census as well as three combined habitat types. RHU-based indicators avoid the potential bias from existing indicator selection methods using subjective selection criteria and are therefore considered as more reliable indicators of ecosystem status.Calculation of a multi-species indicator for each habitat facilitated the classification of an overall temporal trend for each habitat between 1976 and 2010. A comparison of population trends for species with strong habitat associations ('high use species') and more general habitat distributions ('intermediate use species') was performed to determine if these two different groups showed different trends.High-use indicators showed significant declines in bird populations in five out of nine habitats (coniferous, arable, lake, heath and dunes/shore), indicating an ongoing decline in the quality of these habitats. The intermediate use indicator was found to be heavily affected by a proximity effect between habitats and did not prove to be a reliable indicator of ecosystem status. The high use indicators for urban, farmland, freshwater and forest habitats covered 75% of all species included in the Common Birds Census, and with only a minimal species overlap. We conclude that the high use indicator is a useful tool for habitat monitoring and we suggest this set of indicators is used for monitoring the terrestrial and limnic environment in Denmark and abroad.
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