Influence de la mosaïque d'habitats sur l'écologie et la distribution de l'outarde canepetière en Crau

Abstract

The cultivation of the Crau's natural steppe, the "coussoul'', progressively gave place to a mosaic of pastoral and agricultural habitats, especially in the north of the plain. The consequences of these landscape changes for steppe birds are complex : in addition to the reduction and fragmentation of the original habitat, new "modified" habitats, more or less suitable, have developed at the periphery. In this work, I illustrate different aspects of the complementarity between the coussoul and modified agro-pastoral habitats for the little bustard Tetrax tetrax. At the scale of the year-cycle, a complementarity appears between, on the one hand pastoral habitats (coussoul, fallows and grazed crops), with a permanently short sward (<40 cm), accessible to bustards during most of the year, and on the other hand non-pastoral habitats (hay-fields andgrain crops), with marked vegetation dynamics, accessible to bustards at specific times only. Complementarity also exists among modified habitats, which bustards use at different periods of the year depending on vegetation growth. Landscape structure also influences habitat use and distribution of little bustards. In the winter, the use of non-pastoral habitats, where most food resources are found, is limited by the small size of fields (network of hedgerows) which forces bustards to be more vigilant and limits the duration of stopovers. During breeding, the density of displaying males on coussoul increases in the vicinity of the more attractive modified pastures, which partly explains the heterogeneity of bustard distribution within the Craus landscape. The implications of these results in terms of conservation are discussed. In particular, the continuation of extensive farming practices at the periphery of the coussoul appears as an essential complement to the management of the Natural Reserve of the Coussouls of the Crau for the preservation of the bustard population.