Intraspecific competition drives dispersal of an endangered ibis data

Although dispersal drives population dynamics and species distribution, we still know little about how it affects the dynamic of endangered and restricted-range species. After 1981, when the last seven wild individuals of Crested Ibis were discovered in China, the species remained confined to a single location ('original nesting area') until 2000 (< 24 breeding pairs). Then, the breeding population began a significant spatial and numerical expansion (toward the 'secondary nesting area'). Our analyses of long-term (1993–2017) individual-based data (n = 193) show that: (i) natal, but not breeding dispersal, was common (≈77% and ≈2.1%); (ii) as predicted by the intraspecific competition hypothesis, the probability of natal dispersal from the original nesting area increased with increasing and decreasing density at the birthplace and the first breeding site, respectively; nonetheless, (iii) in the secondary nesting area, birth dispersal was density-independent, but (iv) from here they were more likely to disperse, pointing to weak competition at these breeding areas and, since they were all born to dispersing parents, to a role for individual personality; (v) the Weibull distribution provided the best fit to the observed dispersal distances, indicating the presence of long-distance dispersers. We expect the Crested Ibis to continue to spread throughout the region if the protection programs cover a wide range to allow long-distance dispersal. Overall, our study suggests that intraspecific competition can cause dispersal in a population of few individuals confined to a small area and, therefore, be critical for the recovery and expansion of an endangered species.