Breeding biology of the Short-eared Owl (Asio flammeus) in agricultural habitats of southwestern France

Long-term studies of the Short-eared Owl (Asio flammeus) have been conducte d mainly in its central breeding range. We studied its breeding biology in an agricultural habitat in southwestern France, at the southern edge of its breeding range in Europe. The abundance of the main prey species, the comm on vole (Microtus arvalis), varied cyclically. Between 1994-98, breeding wa s only confirmed in 1996, a peak vole year, when 13-19 pairs bred in cereal crop and rye-grass fields. In that year, breeding success was high ((x) ov er bar = 5.7 +/- 0.9 [+/-SD] fledglings per pair), although some young had to be temporarily removed from fields to avoid mortality due to harvesting or mowing activities. The distribution of breeding pairs was clumped. Land use around Short-eared Owl nests included significantly more cereal and sem ipermanent crops (the two cover types with the highest vole densities in 19 96) than expected from random. The spatial distribution of Short-eared Owls was, however, not entirely explained by vole abundance, as there was an ap parent nonrandom spatial association with breeding harriers (Circus spp).