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Aims: Habitat preferences of Barn Owls was studied in two areas of Spain undergoing large-scale habitat alteration.

Location: Alicante (dry cultivations) and Valencia (irrigated cultivations) in eastern Spain.

Methods: Habitat composition around occupied and unoccupied territories in dry cultures and irrigated cultures was compared (n = 71, 1989-2000). This study also described differences n habitat composition between occupied and deserted territories after major habitat alterations started in 1996. Generalized Linear Models were used to examine patterns of habitat preference at three different spatial scales: nest site, home range and landscape.

Results: The study population declined by 69% in both study areas. At the nest site scale, Barn Owls preferred undisturbed areas with high availability of cavities, mainly in man-made structures. At the home range and landscape scales, Barn Owls occupied undisturbed areas with a high availability of cavities and high percentages of edges and ditches. Territory desertion was prompted by the modernisation or disappearance of man-made structures, depletion of edges and ditches, expansion of the road network and persecution. Accordingly, the spatial distribution of territories in irrigated cultures changed fro n uniform to random after habitat alteration. The availability of cavities alone does not account for all of the explained deviance, i.e., Barn Owls occupy structurally complex landscapes.

Conclusions: Compensation measures for habitat loss such as nest-box programs, usually proposed within the framework of environmental impact assessment, are discouraged unless habitat restoration and effective control of persecution are promoted first.