The use of stable isotope technology to study the feathers of migratory birds has become an essential tool for understanding migration patterns. This technique enables researchers to pinpoint the origins of unmarked individuals at stopover sites, offering vital insights into migration routes, stopover behavior, and the environmental conditions influencing these journeys. By analyzing isotopic signatures in feathers, scientists can trace the geographical and ecological factors that shape the migration patterns of various species, even over long distances.In the autumns of 2021 and 2022, migratory bird banding efforts took place in Mingxi County, Sanming City, Fujian Province, which is located along the East Asia-Australasia migration route. This region is critical as a stopover site for numerous migratory species traveling between their breeding grounds and wintering areas. To better understand the migratory behaviors of birds in this area, researchers collected tail feather samples from 20 individuals each of two dominant species: the Eyebrowed Thrush (Turdus obscurus) and the Grey-backed Thrush (Turdus hortulorum). These species were chosen due to their significant presence in the region and their relevance to migration studies.Stable isotope analysis, focusing on isotopes of hydrogen (δ2Hf) and oxygen (δ1?Of), was conducted on the feather samples. These isotopes are sensitive to environmental factors such as water sources, precipitation patterns, and latitude, which provide unique chemical signatures revealing the birds’ breeding origins. Additionally, data on the relative abundance of breeding birds were included to enhance understanding of migration dynamics. Researchers employed Bayesian statistical methods to estimate the spatial probability distribution for both species, aiding predictions about their likely breeding grounds.The study revealed notable differences in the breeding grounds of the two thrush species. The Eyebrowed Thrush primarily breeds in the Lake Baikal region, straddling the border of the Buryatia Republic and Irkutsk Oblast in Russia, with additional populations near the Angara River in Krasnoyarsk Krai. In contrast, the Grey-backed Thrush mainly breeds around Xingkai Lake, located at the border between Heilongjiang Province in China and Primorsky Krai in Russia, along with coastal areas in Primorsky Krai.Furthermore, the analysis uncovered significant differences in the timing of passage through Mingxi between the two species. Statistical testing (T-test, P < 0.01) indicated that in both 2021 and 2022, Eyebrowed Thrushes arrived at the stopover site significantly later than Grey-backed Thrushes. This variation in migration timing is likely linked to differences in the latitudes of their breeding grounds, which affect their migration schedules.Overall, the study emphasizes the power of stable isotope technology in understanding migratory behavior and breeding sources. By elucidating migration timing, routes, and stopover behaviors, this approach contributes valuable insights that can inform future conservation efforts for migratory birds and their critical habitats.