Li Richter, X. | bioRxiv Science

bioRxiv2026

The effects of breeding timing, clutch size, and nesting strategy on reproductive success in the crested ibis (Nipponia nippon)

O_LIStudying the reproduction process, which is a key determinant of individual and population fitness in endangered species, is challenging but urgently needed. The crested ibis (Nipponia nippon), a flagship endangered species recovering from an extreme population bottleneck, provides a valuable opportunity to examine how life-history strategies shape reproductive success and inform future conservation practices. C_LIO_LIWe monitored 176 breeding pairs of crested ibis over three consecutive breeding seasons and investigated the effects of three key life-history traits, namely breeding timing, clutch size, and nesting strategy (solitary versus colonial), on reproductive success (hatching and fledging success). C_LIO_LIOur analysis found that both hatching and fledging success declined significantly as breeding initiated later, and a positive association between clutch size and reproductive success in this species. These patterns were robust and repeatable across three years. Unlike other closely related species in this family, sibling competition is generally non-lethal, leading to large clutch sizes fledged in this endangered species. We consider this pattern to be a main reason underlying the rapid population recovery observed in the crested ibis. On the other hand, nesting strategy (colonial vs. solitary breeding) had no detectable effect on reproductive success. This pattern indicates the crested ibis can adopt different breeding strategies across habitats, highlighting its capacity to flexibly adjust breeding behavior in response to local environmental conditions. C_LIO_LIOur results provide an integrative assessment of how key life-history traits shape reproductive outcomes in a wild population of the crested ibis, serving as a foundation for evaluating its current status of population recovery and refining future conservation strategies for endangered avian species sharing similar life-history characteristics. C_LI

zoology↗

bioRxiv2024

Inbreeding and demography interact to impact population recovery from bottlenecks

Biodiversity loss driven by climate change and human activities poses a critical global challenge. Population restoration and reintroduction programs are essential for mitigating this threat, yet their outcomes are often unpredictable due to poorly understood success factors. The conservation program of the crested ibis (Nipponia nippon) marks a successful example where the population rose from seven survivors to over 9,000 in the past four decades. To learn whether this successful restoration was due to chance or largely repeatable, we developed an individual-based model that simulates the restoration process by incorporating life-history parameters from empirical data. Our simulation results closely mirror empirical findings, including the time taken to reach the current population size and population-level inbreeding coefficients. We further analyzed the model to compare the effectiveness of two reintroduction strategies and analyzed how inbreeding depression interacts with demography to influence the chance of recovery from bottlenecks. The reintroduction simulations reveal that the firework approach (one-source translocations) outperforms the stepping-stone (serial translocations) approach in restoration effectiveness. Our simulations over broad demographic parameters demonstrate that the net effect of inbreeding varies with species-specific demography, and highlight the importance of considering this interaction when interpreting conservation outcomes and designing future reintroduction programs.

ecology↗