Heat tolerances of temperate and tropical birds and their implications for susceptibility to climate warming

Henry S. Pollock; Jeffrey D. Brawn; Zachary A. Cheviron

doi:10.1111/1365-2435.13693

Heat tolerances of temperate and tropical birds and their implications for susceptibility to climate warming

Henry S. Pollock, Jeffrey D. Brawn, Zachary A. Cheviron

Division of Biological and Biomedical Sciences

University of Illinois at Urbana-Champaign

Research output: Contribution to journal › Article › peer-review

52 Scopus citations

Abstract

Characterizing heat tolerance is critical for predicting an organism's vulnerability to climate warming. Recent studies of ectotherms report that impacts of climate warming are expected to be greater in the tropics, where ectotherms tend to have lower heat tolerances and experience air temperatures closer to their heat tolerance limits than their temperate counterparts. However, similar comparisons of heat tolerance are largely lacking for endotherms, and it remains an open question whether climate warming will also disproportionately affect tropical endotherms. To address this empirical gap, we measured thermoregulatory responses to acute heat stress in 81 bird species (23 temperate, 58 tropical), assembling the largest comparative dataset of endothermic heat tolerances to date. After controlling for body mass and experimental chamber humidity, temperate species had significantly higher heat tolerance limits (ΔHTL = 2.2°C; 45.2 vs. 43.0°C) and upper critical temperatures (ΔUCT = 1.1°C; 38.7 vs. 37.6°C) on average than tropical species. Importantly, however, these differences do not appear to impact vulnerability to climate warming, as neither thermal safety margins [i.e. the difference between upper critical temperature (UCT) and maximum air temperature, T_max] nor warming tolerances [the difference between heat tolerance limit (HTL) and T_max] differed between temperate and tropical species. We also observed substantial variation in heat tolerance among avian orders, with pigeons and doves (Columbiformes) being among the most heat tolerant species in our dataset. Overall, our results suggest that, from a physiological standpoint, tropical birds may not be systematically more susceptible to climate warming than temperate birds, contrasting previous studies of ectotherms. Furthermore, we show that certain avian clades may be more resilient to warming irrespective of local climate. However, because we only sampled at one temperate and one tropical site, we caution that replication from other habitats and localities are needed to evaluate the generality of our findings. A free Plain Language Summary can be found within the Supporting Information of this article.

Original language	English
Pages (from-to)	93-104
Number of pages	12
Journal	Functional Ecology
Volume	35
Issue number	1
DOIs	https://doi.org/10.1111/1365-2435.13693
State	Published - Jan 2021

Funding

We thank the Autoridad Nacional del Ambiente (ANAM) for providing research permits to work in the Republic of Panama and the Smithsonian Tropical Research Institute (STRI)—especially Raineldo Urriola, Adriana Bilgray and Owen McMillan, Egbert Leigh and Joe Wright for logistical support. We thank the South Carolina Department of Natural Resources for providing research permits to work in South Carolina and Brett DeGregorio, Chris McBride and especially Tracey Tuberville for logistical support. Access to field and laboratory facilities on the Savannah River Site were made possible by Award Number DE-FC09-07SR22506 from Department of Energy to the University of Georgia Research Foundation. All protocols were approved by the University of Illinois at Urbana-Champaign (#12202), the University of Georgia (#A2013 02-014-Y1-A0) and the Smithsonian Tropical Research Institute (#2013-0101-2016) Institutional Animal Care and Use Committees. We also thank: Blair Wolf, for helpful discussions and insightful guidance on avian thermal physiology; Mark Vukovich for generously allowing us to catch birds at his feeders; and finally, all of the field technicians who helped collect these data, including Yocelin Bello, Fernando Cediel, Noah Horsley, Sean MacDonald, Simon Nockold, Diego Rincón-Guarín, Chris Wagner, Tyler Winter and Kittie Yang. This research was supported in part by an NSF Graduate Research Fellowship, Smithsonian Tropical Research Institute Short-Term Fellowship, Smithsonian Committee for Institutional Cooperation Fellowship and University of Illinois PEEC Summer Research Grant to H.S.P.; a U.S. Army Corps of Engineers Engineer Research and Development Center - Construction Engineering Research Laboratory (ERDC-CERL) grant (#W9132T-11-2-0010) and U.S. Department of Agriculture National Institute of Food and Agriculture Grant (#875370) to J.D.B. The authors declare no competing interests. We thank the Autoridad Nacional del Ambiente (ANAM) for providing research permits to work in the Republic of Panama and the Smithsonian Tropical Research Institute (STRI)—especially Raineldo Urriola, Adriana Bilgray and Owen McMillan, Egbert Leigh and Joe Wright for logistical support. We thank the South Carolina Department of Natural Resources for providing research permits to work in South Carolina and Brett DeGregorio, Chris McBride and especially Tracey Tuberville for logistical support. Access to field and laboratory facilities on the Savannah River Site were made possible by Award Number DE‐FC09‐07SR22506 from Department of Energy to the University of Georgia Research Foundation. All protocols were approved by the University of Illinois at Urbana‐Champaign (#12202), the University of Georgia (#A2013 02‐014‐Y1‐A0) and the Smithsonian Tropical Research Institute (#2013‐0101‐2016) Institutional Animal Care and Use Committees. We also thank: Blair Wolf, for helpful discussions and insightful guidance on avian thermal physiology; Mark Vukovich for generously allowing us to catch birds at his feeders; and finally, all of the field technicians who helped collect these data, including Yocelin Bello, Fernando Cediel, Noah Horsley, Sean MacDonald, Simon Nockold, Diego Rincón‐Guarín, Chris Wagner, Tyler Winter and Kittie Yang. This research was supported in part by an NSF Graduate Research Fellowship, Smithsonian Tropical Research Institute Short‐Term Fellowship, Smithsonian Committee for Institutional Cooperation Fellowship and University of Illinois PEEC Summer Research Grant to H.S.P.; a U.S. Army Corps of Engineers Engineer Research and Development Center ‐ Construction Engineering Research Laboratory (ERDC‐CERL) grant (#W9132T‐11‐2‐0010) and U.S. Department of Agriculture National Institute of Food and Agriculture Grant (#875370) to J.D.B. The authors declare no competing interests.

Funders	Funder number
9132T‐11‐2‐0010
875370
University of Georgia	2013-0101-2016, 2013 02-014-Y1-A0
South Carolina Department of Natural Resources	DE‐FC09‐07SR22506
12202

Keywords

birds
climate warming
endotherms
heat tolerance limit
thermal safety margin
upper critical temperature
warming tolerance

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1111/1365-2435.13693

Cite this

@article{ca3089e49ce146419450d662c6db2d93,

title = "Heat tolerances of temperate and tropical birds and their implications for susceptibility to climate warming",

abstract = "Characterizing heat tolerance is critical for predicting an organism's vulnerability to climate warming. Recent studies of ectotherms report that impacts of climate warming are expected to be greater in the tropics, where ectotherms tend to have lower heat tolerances and experience air temperatures closer to their heat tolerance limits than their temperate counterparts. However, similar comparisons of heat tolerance are largely lacking for endotherms, and it remains an open question whether climate warming will also disproportionately affect tropical endotherms. To address this empirical gap, we measured thermoregulatory responses to acute heat stress in 81 bird species (23 temperate, 58 tropical), assembling the largest comparative dataset of endothermic heat tolerances to date. After controlling for body mass and experimental chamber humidity, temperate species had significantly higher heat tolerance limits (ΔHTL = 2.2°C; 45.2 vs. 43.0°C) and upper critical temperatures (ΔUCT = 1.1°C; 38.7 vs. 37.6°C) on average than tropical species. Importantly, however, these differences do not appear to impact vulnerability to climate warming, as neither thermal safety margins [i.e. the difference between upper critical temperature (UCT) and maximum air temperature, Tmax] nor warming tolerances [the difference between heat tolerance limit (HTL) and Tmax] differed between temperate and tropical species. We also observed substantial variation in heat tolerance among avian orders, with pigeons and doves (Columbiformes) being among the most heat tolerant species in our dataset. Overall, our results suggest that, from a physiological standpoint, tropical birds may not be systematically more susceptible to climate warming than temperate birds, contrasting previous studies of ectotherms. Furthermore, we show that certain avian clades may be more resilient to warming irrespective of local climate. However, because we only sampled at one temperate and one tropical site, we caution that replication from other habitats and localities are needed to evaluate the generality of our findings. A free Plain Language Summary can be found within the Supporting Information of this article.",

keywords = "birds, climate warming, endotherms, heat tolerance limit, thermal safety margin, upper critical temperature, warming tolerance",

author = "Pollock, \{Henry S.\} and Brawn, \{Jeffrey D.\} and Cheviron, \{Zachary A.\}",

note = "Publisher Copyright: {\textcopyright} 2020 British Ecological Society",

year = "2021",

month = jan,

doi = "10.1111/1365-2435.13693",

language = "English",

volume = "35",

pages = "93--104",

journal = "Functional Ecology",

issn = "0269-8463",

publisher = "Wiley-Blackwell Publishing Ltd",

number = "1",

}

TY - JOUR

T1 - Heat tolerances of temperate and tropical birds and their implications for susceptibility to climate warming

AU - Pollock, Henry S.

AU - Brawn, Jeffrey D.

AU - Cheviron, Zachary A.

PY - 2021/1

Y1 - 2021/1

N2 - Characterizing heat tolerance is critical for predicting an organism's vulnerability to climate warming. Recent studies of ectotherms report that impacts of climate warming are expected to be greater in the tropics, where ectotherms tend to have lower heat tolerances and experience air temperatures closer to their heat tolerance limits than their temperate counterparts. However, similar comparisons of heat tolerance are largely lacking for endotherms, and it remains an open question whether climate warming will also disproportionately affect tropical endotherms. To address this empirical gap, we measured thermoregulatory responses to acute heat stress in 81 bird species (23 temperate, 58 tropical), assembling the largest comparative dataset of endothermic heat tolerances to date. After controlling for body mass and experimental chamber humidity, temperate species had significantly higher heat tolerance limits (ΔHTL = 2.2°C; 45.2 vs. 43.0°C) and upper critical temperatures (ΔUCT = 1.1°C; 38.7 vs. 37.6°C) on average than tropical species. Importantly, however, these differences do not appear to impact vulnerability to climate warming, as neither thermal safety margins [i.e. the difference between upper critical temperature (UCT) and maximum air temperature, Tmax] nor warming tolerances [the difference between heat tolerance limit (HTL) and Tmax] differed between temperate and tropical species. We also observed substantial variation in heat tolerance among avian orders, with pigeons and doves (Columbiformes) being among the most heat tolerant species in our dataset. Overall, our results suggest that, from a physiological standpoint, tropical birds may not be systematically more susceptible to climate warming than temperate birds, contrasting previous studies of ectotherms. Furthermore, we show that certain avian clades may be more resilient to warming irrespective of local climate. However, because we only sampled at one temperate and one tropical site, we caution that replication from other habitats and localities are needed to evaluate the generality of our findings. A free Plain Language Summary can be found within the Supporting Information of this article.

AB - Characterizing heat tolerance is critical for predicting an organism's vulnerability to climate warming. Recent studies of ectotherms report that impacts of climate warming are expected to be greater in the tropics, where ectotherms tend to have lower heat tolerances and experience air temperatures closer to their heat tolerance limits than their temperate counterparts. However, similar comparisons of heat tolerance are largely lacking for endotherms, and it remains an open question whether climate warming will also disproportionately affect tropical endotherms. To address this empirical gap, we measured thermoregulatory responses to acute heat stress in 81 bird species (23 temperate, 58 tropical), assembling the largest comparative dataset of endothermic heat tolerances to date. After controlling for body mass and experimental chamber humidity, temperate species had significantly higher heat tolerance limits (ΔHTL = 2.2°C; 45.2 vs. 43.0°C) and upper critical temperatures (ΔUCT = 1.1°C; 38.7 vs. 37.6°C) on average than tropical species. Importantly, however, these differences do not appear to impact vulnerability to climate warming, as neither thermal safety margins [i.e. the difference between upper critical temperature (UCT) and maximum air temperature, Tmax] nor warming tolerances [the difference between heat tolerance limit (HTL) and Tmax] differed between temperate and tropical species. We also observed substantial variation in heat tolerance among avian orders, with pigeons and doves (Columbiformes) being among the most heat tolerant species in our dataset. Overall, our results suggest that, from a physiological standpoint, tropical birds may not be systematically more susceptible to climate warming than temperate birds, contrasting previous studies of ectotherms. Furthermore, we show that certain avian clades may be more resilient to warming irrespective of local climate. However, because we only sampled at one temperate and one tropical site, we caution that replication from other habitats and localities are needed to evaluate the generality of our findings. A free Plain Language Summary can be found within the Supporting Information of this article.

KW - birds

KW - climate warming

KW - endotherms

KW - heat tolerance limit

KW - thermal safety margin

KW - upper critical temperature

KW - warming tolerance

UR - https://www.scopus.com/pages/publications/85092574737

U2 - 10.1111/1365-2435.13693

DO - 10.1111/1365-2435.13693

M3 - Article

AN - SCOPUS:85092574737

SN - 0269-8463

VL - 35

SP - 93

EP - 104

JO - Functional Ecology

JF - Functional Ecology

IS - 1

ER -

Heat tolerances of temperate and tropical birds and their implications for susceptibility to climate warming

Abstract

Funding

Keywords

UN SDGs

Access to Document

Other files and links

Fingerprint

Cite this