On Influencing Factors Of Breeding Dispersal Of A Reintroduced Population Of Crested Ibis (Nipponia Nippon) In Ningshan County

Breeding dispersal is defined as the process of unidirectional movements of individuals between two successive breeding sites.It can increase the breeding success through improving the quality of breeding sites,reducing intraspecific competition and avoiding inbreeding depression,which is a beneficial behavior to individuals and populations.Dispersal ecology has become one of the frontier research fields in avian ecology.At present,preliminary studies on the dispersal ecology have been carried out in the wild and reintroduced populations of Crested Ibis.However,the relationship between breeding dispersal and breeding site quality,individual competition and reproductive success has not been specifically addressed,especially the trade-off between dispersal costs and benefits is still unclear.The present study aims to clarify the effects of breeding site quality,individual competition and reproductive success on breeding dispersal of Ningshan Crested Ibis population,in order to explore the behavior mechanism of breeding dispersal,and provide a theoretical basis for the protection and restoration of breeding sites and the expansion of population distribution.By the end of 2020,a total of 56 breeding pairs of our focused population has formed,in which a total of 81 times of breeding dispersal were displayed by 30 individuals.In this study,based on the reproductive status and results of breeding dispersal,we explored the effects of breeding site quality,individual competition and reproductive success on breeding dispersal.Firstly,the independent variables were analyzed separately;secondly,the factors affecting breeding dispersal were analyzed by using the Generalized Linear Model(GLM).The main results are as follows:(?)In the population,the breeding dispersal rate of females(66.67%,n=24)was significantly higher than that of males(53.85%,n=26)(Fisher's exact test,P=0.041<0.05).In addition,short-distance dispersal is the main form of breeding dispersal,with an average distance of 0.87±1.42 km(n=81).Long-distance dispersal mainly existed in females,and males have high nest-site fidelity.(?)The Ningshan Crested Ibis selects breeding sites with relatively stable requirements for fractional vegetation cover(FVC),altitude and nest height.And the breeding sites with high vegetation coverage and middle-low altitude were preferred.The results of principal component analysis(PCA)showed that the distance from nest site to river,the distance from nest site to road,altitude,aspect and landscape type of breeding site were the key factors affecting the selection of breeding sites.However,the quality of breeding sites has no significant influence on the trend of breeding dispersal at present(Spearman:rs=-0.064,P=0.494,n=117).(?)Due to the fierce intraspecific competition in the nest-intensive areas,the nests of eggs,the chicks fledged numbers,and the breeding success in the nest-intensive areas was all lower than the population average.Besides,breeding dispersal usually took place among individuals nested in the nest-intensive area,and individuals with low breeding success were more likely to dispersal,which is consistent with the avoiding competition hypothesis.(?)Breeding dispersal of Crested Ibis was subject to the chicks fledged numbers and the breeding success.Breeding failure or low breeding success could promote dispersal,which changes the breeding sites and reduces interspecific competition,thereby breeding success and habitat suitability.(?)There was a significant correlation between breeding success and breeding distance in females(Spearman:rs=-0.326,P=0.037,n=42),while there was no significant correlation in males.Male Crested Ibis individuals not only occupy high-quality breeding sites to attract females,but also undertake the tasks of rearing chicks and defencing against natural enemies.Therefore,it is more profitable for them to stay in familiar habitats with high quality than to find new breeding sites.(?)This study provides a preliminary idea for evaluation of the quality of breeding site of Crested Ibis,and also a theoretical basis for the protection of the breeding sites.Extending the suitable habitat area of Crested Ibis is helpful to promote reproduction and dispersal.Therefore,strengthening the protection and restoration of Crested Ibis habitat is a powerful measure to expand the population distribution and maintain stable and sustainable development.As mentioned above,the recommendations we suggested are as follows:(1)Nature reserves should be established to improve habitat quality to increase the carrying capacity.To promote gene flow among populations,it is necessary to reconstruct and restored habitat;(2)we should strengthen the research on Crested Ibis population,fully understand the current situation of the Crested Ibis population,improve individual files and pedigree records,and establish a gene pool;(3)we must improve the population monitoring mechanism,increase capital investment,upgrade tracking equipment,and strengthen monitoring during the breeding period;(4)Laws and regulations associated with management should be publicized,and punishment for illegal activities should be strictly enforced.Publiceducation should be implemented to raise awareness of wildlife conservation.