【Objective】The regulatory mechanism of physical condition on avian migration is one of the research hotspots in current zoology. As a key node of the East Asian-Australasian Flyway (EAAF), the Yancheng Coastal Wetland not only serves as an important migration corridor and stopover site for waterbirds, but also witnesses the passage of a large number of small passerine birds during the spring and autumn migration seasons every year. Based on bird ringing data, this study systematically analyzes the dynamic trends of physical conditions and interspecific differences of small passerine birds during the autumn migration period in Yancheng Wetland from 2018 to 2019 and 2021 to 2023, and further explores the causes of these differences.【Method】Taking three typical dominant warbler species in the region—arctic warbler (Phylloscopus borealis), pale-legged leaf warbler (P. tenellipes), and yellow-browed seawall warbler (P. inornatus)—as research objects, four netting sites with eight mist nets each were set up every 300 m in the coastal forest belt through the ringing network. The body length, body mass, and other parameters of the captured birds were recorded, and a generalized linear model (GLM) was used to analyze the relationship between the first arrival date, peak date, departure date, and the body mass of the warblers.【Result】A total of 796 individuals are ringed during the 5-year monitoring period, and there are extremely significant differences in average body mass among species (Kruskal-Wallis test: χ²=248.145, df=2, P<0.01). Based on time-series dynamic analysis, the body mass of the three bird species all shows a decreasing trend, among which the decreasing trends of P. inornatus and P. tenellipes are extremely significant (GLM: R²(P. inornatus)= 0.2, P < 0.01; R²(P. tenellipes)= 0.1, P < 0.01). The body mass of the three warbler species is significantly negatively correlated with the first arrival date (date when 50% of the population arrives), peak date (date when 75% of the population arrives), and departure date (date when 90% of the population arrives) of the population. Specifically, individuals with larger body mass have significantly delayed population first arrival date (GLM: R²= 0.85, P < 0.01), peak date (R²= 0.81, P < 0.01), and departure date (R²= 0.71, P < 0.01).【Conclusion】As an intuitive indicator of avian energy reserves, body mass significantly affects their migration timing. The significant interspecific differences in body mass among the three warbler species reflect their different energy reserve strategies and ecological adaptation characteristics. The research results provide new scientific evidence for understanding the ecological adaptation of migratory bird migration strategies.