We evaluated the basal metabolic rate (BMR), thermal conductance (C_m), and lower critical temperature (T_lc) of Leach’s Storm-petrel (Oceanodroma leucorhoa) using open-flow respirometry. Measurements were taken from six adults collected at their nests at Great Island, Witless Bay Ecological Reserve, Newfoundland, Canada. In order to establish T_lc and C_m, we determined rates of oxygen consumption after exposing birds to different ambient temperatures (10°C, 20°C, 26°C, and 30°C). Storm-petrels had a minimal C_m of 0.122 ± 0.019 ml O₂/g·°C·h and T_lc was 24°C. The basal rate of oxygen consumption was 1.85 ± 0.24 ml O₂/g·h. Incubating Leach’s Storm-petrels had a basal rate of metabolism lower than previously reported for this species. Possible explanations for this discrepancy include the use of different techniques to measure metabolic rates, and the physiological state of the birds being measured. In this respect, our results coupled with those from previous studies, suggest decreased metabolic rates in incubating Procellariformes compared to those of non-reproducing birds measured at the same temperature. This decline in metabolism is possibly related to metabolic depression due to fasting.