Nocturnal torpor by superb fairy-wrens: a key mechanism for reducing winter daily energy expenditure

摘要: Many passerine birds are small and require a high mass-specific rate of resting energy expenditure, especially in the cold. The energetics thermoregulation is, therefore, an important aspect their ecology, yet few studies have quantified thermoregulatory patterns wild passerines. We used miniature telemetry to record skin temperature ( Tskin) free-living superb fairy-wrens Malurus cyaneus, 8.6 g; n = 6 over N 7-22 days) determine importance controlled reductions body during winter budgets. Fairy-wrens routinely exhibited large daily fluctuations Tskin between maxima 41.9 ± 0.6°C minima 30.4 0.7°C, with overall individual 27.4 1.1°C (maximum range: 14.7 0.9°C). These results provide strong evidence nocturnal torpor this passerine, which we calculated 42% reduction metabolic at Ta 5°C compared active-phase Tskin. A capacity for energy-saving has consequences understanding behaviour life-history ecology fairy-wrens. Moreover, our novel field data suggest that could be more widespread than previously thought within passerines, most diverse order birds.