On the road to self-sustainability: reintroduced migratory European northern bald ibises Geronticus eremita still need management interventions for population viability

The northern bald ibis Geronticus eremita disappeared from Europe in the Middle Ages. Since 2003 a migratory population has been reintroduced in Central Europe. We conducted demographic analyses of the survival and reproduction of 384 northern bald ibises over a period of 12 years (2008-2019). These data also formed the basis for a population viability analysis simulating the possible future development of the northern bald ibis population under different scenarios. We analysed life stage-specific survival rates, rearing protocols and colonies, and the influence of stochastic catastrophic events and reinforcement translocations on population growth. Life stage-specific survival probabilities were 0.64-0.78. Forty-five per cent of the mature females reproduced, with a mean fecundity of 2.15 fledglings per nest. The complementary population viability analysis indicated that the Waldrappteam population is close to self-sustainability, with an estimated population growth rate of 0.95 and a 24% extinction probability within 50 years. Of the 326 future scenarios tested, 94% reached the criteria of extinction probabilities < 5% and population growth rates > 1. Stochastic catastrophic events had only a limited effect. Despite comparatively high survival and fecundity rates the population viability analysis indicated that to achieve self-sustainability the Waldrappteam population needs further translocations to support population growth and the implementation of effective measures against major mortality threats: illegal hunting in Italy and electrocution on unsecured power poles. The findings of this study are to be implemented as part of a second European LIFE project.