Are large-nested bird colonies compatible with the conservation of grazed woodlands?

Abstract

Grazed woodlands provide important ecosystem services (ESs) that contribute to human well-being. Conservation towards protected bird species may sometimes threaten the preservation of protected habitats or the persistence of other threatened species. Studies evaluating the effect of species conservation programs on ecosystem services are yet unusual. Here, we evaluated the effect of white storks (Ciconia ciconia), a gregarious and protected large-nested bird species on the provisioning, supporting and regulating ecosystem services delivered by highly valuable grazed woodlands. We recorded herbaceous floristic composition, net primary productivity (ANPP), organic matter, bulk density, N–P–K, and soil organic carbon under and in-between trees with and without nests in protected grazed woodlands of Spain. We found that white storks only affected the projected area under the nested trees by increasing soil nutrients (N: 1.65-, P:14- and K: 3.40-fold) and grass yield (1.40-fold); and by reducing forage quality (75% reduction in legume yield), plant diversity (60% reduction) and floristic composition heterogeneity (with increased abundance of nutrient-demanding, often invasive, species). Thus, only under the tree canopy (and not in-between trees or ecotone microsites), certain provisioning (forage quality) and supporting (nutrient cycling and biodiversity) ESs decreased. However, large-nested colonies may compromise the long-term conservation of the necessary trees that create and maintain important plant communities underneath. Keywords: Ciconia ciconia, Ecosystem services, Cattle, Ash-dehesa, Nutrient cycling, Herbaceous diversity