Integrating connectivity and habitat availability to identify key wetlands for a critically endangered marsh passerine and guide its national-scale conservation

Abstract Widespread degradation of Mediterranean wetlands has led to dramatic loss of suitable habitats and connectivity between waterbird populations. Multi-scale approaches integrating connectivity and habitat availability can identify areas of high importance to prioritize conservation efforts. Nevertheless, these methods have not been used for small wetland-associated birds, such as Emberiza schoeniclus witherbyi (Eastern Iberian Reed Bunting), a marsh passerine critically endangered in Spain that has almost the entire national breeding population distributed in three apparently isolated wetlands. This study aims to contribute to the national conservation strategy of this species, providing clear management guidelines for decision makers based on habitat availability and connectivity between populations. We analyzed the availability of suitable habitats in 64 Spanish wetlands using a random forest algorithm trained with national census data. Breeding sites were then examined to determine which were the most important wetlands for connecting the current network, as well as how currently unoccupied individual patches could enhance connectivity. Both parameters were integrated to identify priority wetlands for future active management efforts. We found that availability of suitable habitats appears to be limiting the current breeding distribution, with 85% of the population restricted to the three wetlands with largest suitable areas. Two of these wetlands were also the most important metapopulation nodes for connectivity but have associated problems jeopardizing long-term populations sustainability. We identified currently unoccupied wetlands that could be used to increase connectivity, however most had low availability of suitable habitats and would require prior restoration efforts. We provide detailed multi-scale management guidelines to improve national conservation status of E. schoeniclus witherbyi, ranging from wetland-scale restorations to ex situ measures or the need for alternative national water policies that would benefit wetland wildlife.