The effect of microhabitat features, anthropogenic pressure and spatial structure on bird diversity in southern Tunisian agroecosystems

Abstract

Abstract In southern Tunisia, oases and olive orchards are the two main agroecosystems, hence the importance of investigating their value for native fauna. Using generalised linear mixed models, we assessed the relative value of oases and olive plantations over the wintering and the breeding periods by comparing their avifauna diversity using the Shannon diversity index. We also used data on a series of microhabitat features, anthropogenic pressure and spatial parameters to identify the best predictors of bird diversity. In total, 32 species belonging to 18 families were recorded. Sedentary birds accounted for 47% of the counts. Our results showed that bird diversity depends on habitat type, being higher in oases than in olive plantations, but not on the season as no difference was recorded during the two periods of wintering and breeding. The assessment of the effects of microhabitat features, anthropogenic pressure and spatial structure revealed that bird diversity was positively influenced by the cover of trees in oases and olive orchards, negatively affected by distance to edge and that to the paved road in the olive orchards and spatially structured in both agroecosystems. Variation partitioning analysis revealed that the pure effect of microhabitat features (tree cover) was important in explaining the bird diversity both in oases and olive orchards. The identification of factors affecting bird diversity is of great importance for the efficient management of these agroecosystems. Special attention should be paid to keeping a good tree cover. This cannot be performed without: (a) increasing irrigation frequency, (b) adequate tree maintenance (pruning) and (c) reduction of pesticide application. Also, the synergy among owners, farmers, managers and researchers is recommended for the conservation of bird diversity in this North African arid agricultural region.

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