How urban green management is influencing passerine birds nesting in the Mediterranean: a case study in a Catalan city

Abstract

The vegetation within the urban system provides sheltering and food provisions to birds, influencing their nesting options. This study analyses for the first time in the Mediterranean area how different socio-ecological factors related with public urban green management can influence the nesting of the passerine bird order. It uses a case study in the city of Valls (Catalonia, Spain). First, the public urban green was quantitatively and qualitatively characterised; then the nests from the passerine birds were collected and identified, and finally, potential associations between nests and urban green-related socio-ecological factors such as vegetation type (tree, shrub, herb, liana), plant species, neighbourhood type, pruning type, fruit and seed production, and presence of insect plague were analysed. A total of 300 nests were identified and belonged, mostly, to the family of Fringillidae and Sylviidae, all from Mediterranean agroforestry areas. Passerine birds show preference for the historic centre, being this area the one with highest biodiversity of vegetation in the city, in detriment of surrounding neighbourhoods, which in turn are less biodiverse. Passerine birds do not consider four tree species (Celtis australis, Laurus nobilis, Robinia pseudoacacia and Pinus pinea) suitable for nesting whereas showing preference for two tree species of medium height and size (Hibiscus syriacus and Melia azederach). Also, passerine birds seem to preferably nest in trees that have been pruned intensively. These results suggest that, to strengthen the passerine bird diversity in cities, urban green management should promote certain species of trees of medium size and intensive pruning while supporting the overall biodiversity of the urban green. All these results contribute to inform effective urban planning and management strategies for passerine birds conservation that aim to reconcile urban development and urban biodiversity protection.