Climate change is increasing the frequency and magnitude of extreme weather events, reducing the predictability of food and water availability for animals. Understanding how endotherms balance energy and water during periods of resource scarcity is critical for predicting species resilience. The red-headed finch (A. erythrocephala) roosts communally and uses shallow rest-phase hypothermia to conserve energy when food-deprived, but the energetic benefits of huddling behaviour and responses to water shortages are unknown in this species. We examined energy-conservation strategies by measuring metabolic rate (MR) and body temperature (Tb ) of finches (n=30) at air temperatures (Ta )≈10–20°C in solitary birds, pairs, and groups of four, when finches were either well-fed or food-deprived. Well-fed individuals maintained normothermic Tb but had lower MR when huddling in groups. Food-deprived birds used shallow rest-phase hypothermia regardless of group size (minimum Tb =32.8°C). The greatest energy savings occurred when both strategies were used concurrently, with hypothermic birds huddling in a group of four saving >50% of energetic costs relative to normothermic, solitary individuals. We also examined the effect of water shortages on evaporative cooling capacity, by measuring evaporative water loss (EWL), MR, and Tb in well-hydrated and water-deprived finches (Ta ≈30–42°C; n=20). Water-deprived birds significantly reduced EWL but maintained similar Tb and MR to well-hydrated birds. This suggests that birds can reduce their water costs while maintaining normothermic Tb , but the mechanistic basis is unclear. These physiological and behavioural responses likely help birds maintain energy and water balance, increasing their survival during resource-scarce periods and extreme weather events.