Importància dels guarets ambientals com a font d'insectes per a la conservació del sisó (Tetrax tetrax) i altres ocells esteparis en els secans cerealístics

Abstract

Farmland ecosystems of Western Europe (including the dryland cereal pseudo-steppes, with a rich and seriously endangered community of steppe birds) have undergone a great intensification process which has led to sharp decreases in the communities of plants, birds and insects. These, especially orthopterans, are the staple diet of many steppe birds, including some strictly herbivorous species whose chicks rely mainly on insects during their first weeks of live, such as the little bustard (Tetrax tetrax). Although field edges are key invertebrate source habitats, as well as for biodiversity conservation in general, they may not compensate for the loss and homogenization of landscape in intensified farmland. The introduction of wildlife fallows within the cereal matrix can be a very useful tool to diversify the landscape in excessively homogeneous areas. In the case of the little bustard, to provide display, nesting and feeding areas for adults and chicks. To reverse the negative situation of the little bustard in Catalonia, in 2006 a program was started in the SPA Belianes- Preixana (among others) to implement wildlife fallows, either with natural or sown with alfalfa. To evaluate the results of this actions, between 2010 and 2012 we conducted a total of 140 Orthoptera and Lepidoptera counts in different habitats in late June-early July, coinciding with the chick little bustard growing period. The results show that the wildlife fallows have the highest abundance of orthopterans and lepidopterans, followed by plots with barley stubble and, finally, plough fields. Thus, wildlife fallows, especially those sown with alfalfa, have on average between 2.5-4 times more orthopterans than unharvested cereal fields, between 9-14 times more than cereal stubble fields. Orthopterans are virtually absent from plough fields. A similar, though less marked, pattern is also observed in the lepidopterans. The amount of rain in late winterspring seems to be an important parameter to account for the number of arthropods in the different habitats, especially in the wildlife fallowsimwith alfalfa. To conclude with, we believe that the establishment of wildlife fallows is a positive management practice to promote arthropod populations in farmland, which can also have positive effects to improve the reproductive success of the little bustard and other steppe birds in areas intensified cereal.