Breeding success of White Storks Ciconia ciconia after reintroductionin Alsace

摘要

In the mid 1970s, the breeding populations of the migrant White Stork (Ciconia ciconia) were close to extinction in North-East of France (Alsace). A reintroduction project, implemented with a majority of eggs and young from Maghreb, resulted in the settlement of some individuals. Both settled and migrant birds breed today in the same areas and rely on food from rubbish dumps. Since the onset of the population decline, the reproductive success decreased until today. This lower reproductive year to year may have resulted from some factors in the environment, the lower reproductive success of white storks from Maghreb and the modifications in behaviour (settled vs. migrant). The aim of this work was to test the last factor, i.e. the influence of bird behavior and of food availability (control nests vs. nests near rubbish dumps) on reproductive success. For all nests, the numbers of eggs and hatchlings were higher in settled birds than in migrants, this difference resulting only from the earlier breeding of settled storks. The large broods of settled birds showed a high mortality rate, leading to the same fledgling success (fledglings/hatchlings) and number of fledglings as in migrants. Fledgling success and number of fledglings were higher for nests close to a food supply. To sum up, although settled birds can breed earlier and produce more eggs, we found no advantage in terms of number of fledglings. The higher mortality rate found in large broods could be induced by the deterioration of their habitat.