Nest boxes for raptors in Natura 2000 farmland: demonstrating the biological control of the common vole in Spain

About the finalist 

Overview 

Large areas of cereal-planted steppe in the central area of the Spanish Northern Plateau are regularly ravaged by outbreaks of the common vole. These pest outbreaks cause significant damage to crops, and present health concerns due to the potential transmission of infectious diseases. Traditionally, farmers and regional authorities have tackled the problem by using chemical rodenticides. However, not only were the pesticides ineffective, they were also expensive and had negative environmental impacts. 

Between 2009 and 2023, the Spanish NGO GREFA, in collaboration with the Spanish Ministry of Ecological Transition and the Government of Castilla y León, promoted an alternative approach: the use of native birds of prey to manage the common vole.  

Such biological control was initially not readily accepted by some farmers, because raptors work in relatively discrete way compared to the conspicuous results of poison and other measures such as controlled fire. Hunters, on the other hand, were more positive about the new approach, because it avoided the losses of game species to poisoning. Meetings and talks with local community members, including landowners and farmers, allowed a consensus to be reached on discontinuing previous practices and trialling new methods.  

As a result, hundreds of nest boxes were installed on croplands in the Natura 2000 sites ‘Campos-Nava Norte and Sur’, ‘Lagunas de Villafáfila’ and ‘Campos de Alba’. The nest boxes provide adapted nesting sites, shelter and perches for the barn owl (Tyto alba), the common kestrel (Falco tinnunculus), the little owl (Athene noctua) and the lesser kestrel (Falco naumanni). These natural predators of the common vole would otherwise find hardly any nesting or roosting opportunities in these highly intensified agricultural landscapes. 

Annual monitoring of raptor offspring and nest occupation rates - which in several cases has reached over 90% - has shown a high overall effectiveness of the method, with birds of prey adapting their presence and reproductive effort to the natural fluctuations of the vole population. 

As a result of this initiative, biological control is now considered a valid, economical, long-lasting and environmentally-friendly alternative to traditional rodent pest management tools. In addition, this new method is also a conservation tool, as it provides important support for birds of prey such as the barn owl, which is declining in Spain. 

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