Hot days are associated with short-term adrenocortical responses in a southern African arid-zone passerine bird

Lesedi L Moagi; Amanda R Bourne; Susan J Cunningham; Raymond Jansen; Celiwe A Ngcamphalala; André Ganswindt; Amanda R Ridley; Andrew E McKechnie

doi:10.1242/jeb.242535

Hot days are associated with short-term adrenocortical responses in a southern African arid-zone passerine bird

J Exp Biol. 2021 May 15;224(10):jeb242535. doi: 10.1242/jeb.242535. Epub 2021 May 25.

Authors

Lesedi L Moagi^{1

2}, Amanda R Bourne³, Susan J Cunningham³, Raymond Jansen⁴, Celiwe A Ngcamphalala^{1

5}, André Ganswindt⁶, Amanda R Ridley⁷, Andrew E McKechnie^{1

5}

Affiliations

¹ South African Research Chair in Conservation Physiology, National Zoological Garden, South African National Biodiversity Institute, Pretoria 0001, South Africa.
² Department of Nature Conservation, Tshwane University of Technology, Pretoria 0001, South Africa.
³ FitzPatrick Institute of African Ornithology, DSI-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa.
⁴ Department of Environmental, Water and Earth Sciences, Tshwane University of Technology, Pretoria 0001, South Africa.
⁵ DSI-NRF Centre of Excellence at the FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.
⁶ Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.
⁷ Centre for Evolutionary Biology, School of Biological Sciences, University of Western Australia, Crawley, Perth, WA 6009Australia.

PMID: 34032270
DOI: 10.1242/jeb.242535

Abstract

Relatively little effort has been directed towards elucidating the role of physiological stress pathways in mediating avian responses to global heating. For free-ranging southern pied babblers, Turdoides bicolor, daily maximum air temperatures (Tmax) between ∼35 and ∼40°C result in reduced foraging efficiency, loss of body mass and compromised breeding success. We tested the hypothesis that very hot days are experienced as stressors by quantifying relationships between Tmax and faecal glucocorticoid metabolite (fGCM) levels in naturally excreted droppings. On days when Tmax<38°C, fGCM levels were independent of Tmax (mean±s.d. 140.25±56.92 ng g-1 dry mass). At Tmax>38°C, however, fGCM levels increased linearly with Tmax and averaged 190.79±70.13 ng g-1 dry mass. The effects of Tmax on fGCM levels did not carry over to the following morning, suggesting that very hot days are experienced as acute stressors.

Keywords: Air temperature; Desert; Faecal glucocorticoid metabolites; Fitness costs; Heat stress.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Body Temperature Regulation
Glucocorticoids
Hot Temperature
Passeriformes*
Stress, Physiological
Temperature

Substances

Glucocorticoids