Can interspecific competition and nest site availability explain the decrease of lesser kestrel Falco naumanni populations?

Abstract

The population decline of the lesser kestrel, a globally threatened species, has been sometimes explained on the basis of interspecific competition and lack of suitable nest-sites. Our results from a three-year study of 674 kestrel colonies in northeastern and south Spain showed that nest-site cavities were not a scarce resource even in decreasing populations. The presence of presumptive competitors (jackdaws Corvus monedula and feral pigeons Columba livia) did not limit nest-site availability. Breeding success was not lower in colonies with competitors than in colonies where the species breeds alone. We conclude that neither the lack of cavities nor the effects of interspecific competition can satisfactorily explain the global decline of lesser kestrel populations.