Winter thermoregulation in free‑ranging pygmy falcons in the Kalahari Desert

Jess Lund, Diana Bolopo, Robert Thomson, Dorianne Elliott, Luke Arnott, Ryno Kemp, Anthony Lowney, Andrew McKechnie

Research output: Contribution to journalJournal Articlepeer-review

5 Citations (Scopus)


Among birds, pronounced heterothermy tends to be used by small species belonging to phylogenetically older taxa and inhabiting environments with unpredictable and/or seasonally scarce food resources. Previous evidence suggests that a small arid-zone raptor, the pygmy falcon (Polihierax semitorquatus), enters torpor and decreases its body temperature (Tb) to below 31 °C on winter nights in the Kalahari Desert, where sub-zero night-time temperatures occur regularly. To confrm that this species has the capacity for heterothermy and to characterise its thermoregulatory patterns under natural conditions, we implanted temperature-sensitive radio transmitters into free-ranging falcons. Based on data from seven individuals, we found no evidence for the substantial reductions in Tb previously reported. The mean minimum rest-phase Tb during the study period was 37.89±0.67 °C, we observed no instances of Tb<36 °C, and air temperature did not signifcantly infuence patterns of thermoregulation. Our results highlight intraspecifc variability in heterothermy among birds and reveal that, contrary to previous suggestions, even in mid-winter pygmy falcons may not reduce Tb below normothermic levels.
Original languageEnglish
Pages (from-to)549-555
Number of pages7
JournalJournal of Ornithology
Issue number2
Publication statusPublished - 29 Feb 2020
Externally publishedYes


  • Body temperature
  • Falconidae
  • Heterothermy
  • Telemetry
  • Torpor


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