Riquesa d'espècies i interès per a la conservació dels ocells a l'àrea metropolitana de Barcelona: relacions amb la xarxa actual d'espais protegits

Abstract

The spatial distribution of bird species richness and its relationship with several territorial variables and with the distribution of nature reserves was analysed for three species groups of differing interest for conservation: (1) all species, (2) species with an unfavourable conservation status in Europe (categories 2 and 3 of SPEC; SPEC2+3), and (3) species included in Annex I of the Birds Directive. The study was carried out in the Vallès Oriental and surrounding areas, in the metropolitan area of Barcelona. Bird species numbers were obtained for each UTM 1 × 1 km square from a previous field survey carried out separately for nesting (spring) and wintering species (winter) over an 8 year period. The relationships between the different groups and between these and the most relevant territorial variables were assessed using Pearson correlations. The numbers of species and the territorial variables for areas inside and outside the nature reserves were also compared, using a random subsample of squares. The total species richness and the number of SPEC2+3 species were, in most cases, significantly higher outside the nature reserves and were concentrated in forest-cropland mosaics in the Moianès and Osona for the nesting species and in the Vallès plain for the wintering ones. All these species groups showed significant positive correlations with cropland and land cover diversity. The number of SPEC2+3 species was moderately correlated with total species richness. In contrast, the species richness of species included in the Birds Directive showed some hot spots in the Montseny natural park, and consequently was weakly correlated with the total species richness and the number of SPEC2+3 species. The study shows a complex conservation situation in the Vallès Oriental, with nature reserves harbouring several species included in the Birds Directive, while forest-cropland mosaics that are very species-rich are not especially protected. There is a clear need to promote and