Disentangling the effects of management, field characteristics of fallows, and surrounding landscape to promote steppe bird conservation

The steep decrease of fallow area in the last years has been directly related to steppe bird population declines in Europe, as fallow lands are a crucial habitat for shelter, food, and nesting resources. However, the potential of fallows to foster steppe bird populations may vary greatly depending on factors at both the landscape and field scale, which may also interact differently depending on the species. This study uses data from more than 3000 ha of fallow land in north-eastern Spain specifically managed for steppe bird conservation to explore which are the characteristics that maximize their conservation value for steppe bird species. We used variance partitioning methods to separate the effects of fallow management (e.g., vegetation height or fallow age) from field characteristics (e.g., field size) and landscape context (e.g., amount of surrounding shrubland area) on the occurrence and abundance of target steppe bird species. Even if fallow management was optimized to meet the requirements of steppe birds, field characteristics and landscape context had important effects (i.e., explained high part of the variance) in maximizing occurrence and abundance. All studied species consistently preferred bigger and dominant fallows (i.e., those at a higher relative elevation). Conservation measures promoting fallows for the conservation of steppe birds should consider mechanisms to optimize the selection of fields. Integrating optimal field selection might be too specific and challenging for agri-environment-climate measures (AECM), however it could be a cost-effective measure when implemented in local or targeted conservation plans, such as those applied within priority areas, protected areas, or compensatory measures.