Tiny radio transmitters reveal a hidden survival tactic in birds

Researchers used miniature (400 mg) temperature‑sensing radio transmitters and nighttime radio‑tracking in Sturt National Park (near Tibooburra, central Australia) to monitor body temperature of white‑backed swallows in their sandy burrows across the winters of 2023-24. Continuous data from autonomous loggers showed these passerines entered deep, prolonged bouts of torpor during cold, wet conditions, sometimes remaining in burrows through the daytime. These torpor episodes far exceeded what passerines were thought capable of and provided an energy‑saving response when flying insects - their food - were suppressed by rain and low temperatures. The work is reported in Current Biology.

The findings overturn assumptions that deep torpor is limited to some northern‑hemisphere or specialist species and demonstrate how modern biologging reveals hidden physiological strategies. Comparable recent biologging results show other unexpected thermal tactics in birds and mammals - such as large flying foxes using torpor in winter and controlled rises in body temperature during heat - to cope with extreme weather. This expands understanding of avian resilience and has direct relevance for predicting species’ responses to increasingly frequent and severe climate extremes.