Sympatric closely related species may experience interspecific trophic competition due to ecological similarity; they may isolate in terms of diet or habitat use as a strategy to avoid competition. The body tissues of consumers contain stable isotope signatures information that can be applied to infer their dietary information. In this study, δC and δN stable isotopes were analyzed to determine the dietary information and trophic niches of sympatric coexisting and . The results showed that the food sources of and were from six orders, including Orthoptera, and the cumulative contribution rate was 99.97%, with the two species eating similar diets but at different rates. The larger δC of indicates that it had a wider range of habitats for feeding, while the difference in δN values was not significant ( > 0.05), indicating that both species feed on similar nutrient levels. As determined by Bayesian ellipses, the isotopic niches of and were differentiated; the isotopic niche width of is 2.69‱, which was larger than that of (0.73‱), indicates that differentiation between the two species in diet or habitat use reduced competition. Trophic niche differentiation and differences in foraging proportions may be the principal resource allocation mechanisms behind and coexistence.