The importance of university campuses for the avian diversity of cities

In a world of increasing urban areas and their subsequent negative effect on biodiversity, university campuses arise as environmentally friendly designs that can help enhancing biodiversity. However, current information on the topic is mainly based on single-campus studies, taxonomic diversity variables (e.g., species richness), and specific geographic regions like Asia or North America. Multi-campus comparisons, studies on other components of biodiversity (e.g., functional or phylogenetic diversity) and biodiversity information from other regions of the world are needed to generalize the previous findings. In this study we try to fill in these gaps by simultaneously investigating taxonomic, functional, and phylogenetic diversity of bird communities on 15 university campuses of Spain, which is located within the Mediterranean hotspot of biodiversity where no previous studies on this topic have been conducted. We compared campus areas with other randomly selected urban areas to test whether university campuses hold higher levels of bird diversity than non-campus areas. We also analyzed other environmental variables (e.g., green and building cover in and around campuses) to identify whether their influence in university campuses varies from other urban areas. Our results show that taxonomic diversity was higher within university campuses compared to other areas, but this pattern was not confirmed for functional and phylogenetic diversity. We found that grass cover, buildings, and the green area around the study areas have different associations with taxonomic, functional, or phylogenetic diversity respectively in campuses or non-campus areas. Our findings highlight the importance of university campuses for the conservation of Mediterranean urban biodiversity and support their use as relevant resources for promoting nature conservation among citizens.