Preliminary results of the effect of raptor nest boxes in dryland agricultural landscapes during a common vole outbreak

Abstract

During last decades, the common vole (Microtus arvalis Pallas) colonized the agricultural lands of the Spanish northwestern plateau, where population outbreaks have occasionally caused significant crop damages. In these agroecosystems, there is an apparent imbalance in the relationship between avian predators and prey, probably influenced by a lack of adequate areas for the establishment, breeding and hunting of raptors. This is one of the causes that may be influencing common vole population dynamics, and causing crop damages. Thus, landscape modification to increase natural vole avian predators, could be an environmentally-friendly preventive tool to be considered into an integrated pest management strategy. An important question to be answered is the efficacy of this measure during a vole outbreak, when vole numbers would increase faster than those of their predators. Two different locations (Osorno la Mayor and Villarramiel) were provided with 100 nest-boxes (50 for barn owl and 50 for common kestrel) distributed in a 2000 ha surface. The effect of boxes in voles was studied considering the different habitats linked to these agricultural zones, including crops and vole reservoirs. During the campaign 2013/14, a common vole outbreak was detected in these areas. Considering the period between sowing and harvesting winter crops, data of distances, densities, raptor occupancy and breeding in nest-boxes, were used to generate informative covariates to be related with indexes of vole activity. In this contribution, preliminary results about the effect of the implementation of nest-boxes for raptors on the evolution of common vole abundance are reported.