Many avian parents temporarily abandon incubation duties, leaving the developing embryo to ambient thermal conditions from several hours up to several consecutive days with little or no effect on hatchability. The hypothermic tolerance of the eggs in passerines is poorly known. Three abnormally long off-bouts (4.45 h, 1.17 h and 5.32 h bouts, respectively) were observed in an incubating Slaty-blue Flycatcher (Ficedula tricolor) female at the Lianhuashan Natural Reserve, Gansu Province, China. The nest temperature was measured and recorded by a temperature data logger at 50-second intervals. During the absences the nest temperature dropped to a minimum of 7.7℃ and included two periods (3.83 h and 4.60 h) when nest temperatures were below 10℃. Nest attendance resumed thereafter and continued normally until the eggs hatched.