Seasonal metabolic adjustments in an avian evolutionary relict restricted to mountain habitat

Krista N. Oswald, Alan T.K. Lee, Ben Smit

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

For endotherms, maintaining body temperature during cold winters is energetically costly.Greater increase in winter maximum thermogenic capacity (Msum) has typically been correlated with improved cold tolerance. However, seasonal studies have shown equivocal direction change in basal metabolic rate (BMR) in winter, perhaps explained by latitude or phylogeny. We examined seasonal metabolic responses in the Cape rockjumper (Chaetops frenatus; “rockjumper”), a range-restricted mountain bird. We hypothesized that, given their mountain habitat preference, rockjumpers would be physiologically specialized for cooler air temperatures compared to other subtropical passerines. We measured body condition (using the ratio of Mb/tarsus), BMR, and Msum, in wild-living rockjumpers during winter and summer (n = 12 adults in winter –– 4 females, 8 males; n = 12 adults in summer –– 6 females, 6 males). We found birds had lesser BMR and thermal conductance, and greater Msum and body condition, in winter compared to summer. These changes may help rockjumpers conserve energy in winter while still allowing birds to produce more metabolic heat during the coldest air temperatures. When compared with existing data on avian seasonal metabolic adjustments, rockjumper BMR fit general patterns observed in passerines, but their Msum was low compared with other members of the oscine Passeriformes. These patterns may be explained by the narrow temperature range of their habitat not requiring cold-adjustment, or perhaps by their basal placement within passerine phylogeny. Further work on the physiological phenotypic plasticity in habitat specialists across different latitudinal zones and taxa is needed to better understand the relationship between metabolism, habitat, and phylogeny.

Original languageEnglish
Article number102815
JournalJournal of Thermal Biology
Volume95
DOIs
StatePublished - 1 Jan 2021
Externally publishedYes

Keywords

  • Avian metabolism
  • Avian phylogeny
  • Basal metabolic rate
  • Seasonal physiological responses
  • Summit metabolism

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Agricultural and Biological Sciences (all)
  • Developmental Biology

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