Is the reintroduced white stork (Ciconia ciconia) population in Switzerland self-sustainable?
Résumé
The migratory white stork (Ciconia ciconia) became extinct in Switzerland in 1950. A reintroduction project with intensive management (translocation, prevention of migration, artificial feeding) started in 1948, and 175 pairs were breeding in 2000. For the period 1973-2000 we estimated annual survival rates and fledging success to estimate the population growth rate by a stochastic matrix projection model. Compared to other populations, adult survival rate (0.86, with 95% CI: 0.81-0.89) was very high and little variable over time, juvenile survival (0.37, CI: 0.31-0.43) was comparable to other populations whereas the average fledging success was low (1.65) but strongly variable over time. The population growth rate was positive, indicating that the population is self-sustainable at the moment. The growth of the white stork population was largely favoured by the high adult survival which more than compensates for the low fledging success. The population growth rate is particularly sensitive to changes in adult survival, but it would be very difficult to improve this further with management. However, maintenance of the high adult survival is crucial and an improvement in fledging success seems important for the long-term persistence of the white stork population in Switzerland. Fledging success depends on habitat quality, and thus restoration of breeding habitats should be the main management activity in the near future.