Bird bite force could be an indication of evolutionary adaptation in avian head and beak morphology, and thus an important indicator of ecological adaptation characteristic such as food type, intraspecific competition and predation pressure. However, there has been little work on bird bite force and its influencing factors. In this study, we compared bite forces of two sister sparrow species from the Passeridae family, the Tree Sparrow (Passer montanus) and Russet Sparrow (P. cinnamomeus), by using a bite force transducer. The results showed that bite force of Russet Sparrow (n = 12) was significantly stronger than that of Tree Sparrow (n = 59) (Fig. 1, t = 3.754, P < 0.01), however, there was no difference in sex of Russet Sparrow (t = 0.449, P > 0.05) or Tree Sparrow (Z =﹣1.198, P > 0.05) (Fig. 2).The head width (t =﹣3.713, P < 0.01), head depth (t =﹣5.405, P < 0.01) and beak width (t =﹣6.201, P < 0.01) of the Russet Sparrow were also much bigger than those of the Tree Sparrow (Table 1). Although our results showed that the bite force was not related to any body parameter in individuals of the two sparrow species (Table 2), it was indicated that head size and bill width might be related to the bite force in interspecific species competition. The difference in bite force of these two sparrow species may be due to their different habitats and food types. To the best of our knowledge, our work is the first quantitative study of bird bite force in China.