ABSTRACT As top predators and environmental sentinels in marine ecosystems, seabirds face significant pressure from global fisheries in competing for fish resources. For the critically endangered Chinese crested tern ( Thalasseus bernsteini ), characterizing its dietary requirements is a fundamental step in assessing how food availability and potential fishery‐induced resource shifts may impact its recovery. This study, conducted on breeding islands (Xiangshan island and Nanji Island) in Zhejiang, analyzed 12S and COI regions from fecal samples ( n = 50) using DNA metabarcoding technology to systematically analyze the diets of mixed‐colony terns (Chinese crested terns and greater crested terns T. bergii ) across the breeding season (breeding stage and nestling stage). The results for both species combined revealed a highly specialized diet, primarily focused on epipelagic schooling fish, with Engraulidae (occurrence frequency, FO = 72.73%) and Scombridae (FO = 27.27%) being the dominant taxa (combined relative read abundance, RRA > 54%). The key species were Engraulis japonicus , Setipinna tenuifilis , and Thryssa kammalensis . Our multi‐scale taxonomic analysis revealed that the dietary structure of these terns was conserved at higher taxonomic levels but highly dynamic at the species level. PCoA indicated no significant segregation between breeding stages or islands at the family level, whereas distinct, significant differences emerged between breeding stages at the species level, with nestling‐stage diets exhibiting greater diversity (significant higher Chao index), reflecting increased flexibility in resource utilization during the provisioning period. By integrating our findings with data from Australia and South Africa, we identify a universal foraging characteristic of T. bergii and T. bernsteini as a specialist predator primarily dependent on epipelagic schooling fish across its global range. Although the waters surrounding the study islands serve as an important spawning ground for various commercial fish species, the diet of these terns contains economically valuable fish in very low proportions (relative sequence abundance < 5%), indicating niche separation from direct fishery competition. Additionally, the first detection of freshwater fish in 6.82% of samples (3 out of 44) in the tern diet within this study area highlights the behavioral plasticity of terns in human‐modified environments and the potential for novel human‐bird conflicts at these sites. Our study emphasizes that securing these shared prey resources, particularly Engraulidae, is essential for the breeding success of these mixed colonies. Conservation strategies must extend beyond traditional habitat protection to incorporate coastal human activities into risk management frameworks, thereby enhancing the recovery of the critically endangered Chinese crested tern by protecting its primary food base.
Ding et al. (Wed,) studied this question.