Common Cuckoo (Cuculus canorus) is an obligate brood parasitic bird that has evolved a series of adaptions, such as cuckoo chicks could hatch earlier and eject the host eggs, to exploit more of the hosts. In this study, we collected fresh eggs of the Common Cuckoo (n = 25) and its host Oriental Reed Warbler (Acrocephalus orientalis) (n = 20), and incubated them in an automatic incubator with constant temperature of 37.8 ℃. All eggs were measured soon after collection and the egg mass was weighted daily during the incubation using an electronic balance. Our results showed that hatching success of the Common Cuckoo (76%) was significantly higher than that of the Oriental Reed Warbler (40%; Chi-square, χ2 = 25.144, df = 1, P < 0.01), implying that the ecological amplitude of the embryonic development temperature of the Common Cuckoo might be wider than the host, and the incubation temperature tolerance of Cuckoo might be stronger than the host. Although the fresh egg mass (Independent-samples T test, t = 7.447, df = 43, P < 0.01) and egg volume (t = 7.447, df = 4, P < 0.01) of the Common Cuckoo were much larger than those of the Oriental Reed Warbler (Fig. 1), there was no significant difference in incubation period between the two species.