Adaptation du comportement de nidification chez le faucon crécerellette Falco naumanni en réponse a la compétition avec le choucas des tours Corvus monedula / Adaptations of Lesser Kestrel Falco naumanni nesting behaviour in response to competition with Jackdaws Corvus monedula

The population of Lesser Kestrel Falco naumanni in France decreased by 90% between 1947 and 1980. In the Crau, an arid region of southern France, the species has been known to breed since 1959 but the existence of a population of some tens of pairs is a new phenomenon. During the 1980's this expanding population bred only in sheepfolds, but since the arrival of Jackdaw Corvus monedula in 1986, it started breeding in stone heaps, which were predominantly used in 1992 and are now the only breeding sites. A study of comparative fledgling success in sheepfolds with and without Jackdaws shows some differences, but the fledgling rates are close to those of an expanding population and these differences alone are not sufficient to explain the observed decrease and extinction of the main colony in a sheepfold in which Jackdaws had started breeding. We think that disturbance by Jackdaws, competition for nest-holes and availability of other breeding sites explain the decrease in this colony.