CAN INTERSPECIFIC COMPETITION AND NEST-SITE AVAILABILITY EXPLAIN THE DECREASE OF LESSER KESTREL FALCO-NAUMANNI POPULATIONS

The population decline of the lesser, kestrel, a globally threatened s pecies, has been sometimes explained on the basis of interspecific com petition and lack of suitable nest-sites. Our results from a three-yea r 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) din not limit nest-site ava ilability. Bleeding success was not lower in colonies with competitors than in colonies where the species bleeds alone. We conclude that nei ther the lack of cavities nos the effects of interspecific competition can satisfactorily explain the global decline of lesser kestrel popul ations. Copyright (C) 1996 Elsevier Science Limited