Cambios poblacionales de una comunidad de aves esteparias en una localidad del centro de España en un periodo de 35 años

Abstract

The inter-annual changes in a breeding community of steppe birds are analysed in an area used for growing cereal crops in central Spain (Sepúlveda, province of Segovia). The data come from eight routes in which the uses (pasture, fallow, ploughed land and cornfield substrates) of the agricultural plots were recorded, and the birds censused during the spring of 1984, 2015, 2016 and 2019, assigning the observations to one of the four agricultural substrates or to field borders. The structure of the agricultural landscape did not change, but the agricultural uses varied from one year to another, mainly as a result of changes in ploughed and cornfield areas. An increase was found in bird richness and significant changes in the density of several species, with significant declines in the calandra lark, and less clear temporal trends in other species. The variation between substrates with regard to density and Ivlev’s electivity index showed that pastures and field borders benefited a majority of species, while ploughed and fallow fields each had positive effects on a single species (the greater short-toed lark and the common linnet, respectively). Cornfields were rejected, or used according to their availability. In conclusion, the importance of stable elements in agricultural landscapes (pastures and field borders) for breeding populations of steppe birds is emphasised