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Avian thermoregulation in the heat: evaporative cooling in five Australian passerines reveals within-order biogeographic variation in heat tolerance.
J Exp Biol. 2017 07 01; 220(Pt 13):2436-2444.JE

Abstract

Evaporative heat loss pathways vary among avian orders, but the extent to which evaporative cooling capacity and heat tolerance vary within orders remains unclear. We quantified the upper limits to thermoregulation under extremely hot conditions in five Australian passerines: yellow-plumed honeyeater (Lichenostomus ornatus; ∼17 g), spiny-cheeked honeyeater (Acanthagenys rufogularis; ∼42 g), chestnut-crowned babbler (Pomatostomus ruficeps; ∼52 g), grey butcherbird (Cracticus torquatus; ∼86 g) and apostlebird (Struthidea cinerea; ∼118 g). At air temperatures (Ta) exceeding body temperature (Tb), all five species showed increases in Tb to maximum values around 44-45°C, accompanied by rapid increases in resting metabolic rate above clearly defined upper critical limits of thermoneutrality and increases in evaporative water loss (EWL) to levels equivalent to 670-860% of baseline rates at thermoneutral Ta Maximum cooling capacity, quantified as the fraction of metabolic heat production dissipated evaporatively, ranged from 1.20 to 2.17, consistent with the known range for passerines, and well below the corresponding ranges for columbids and caprimulgids. Heat tolerance limit (HTL, the maximum Ta tolerated) scaled positively with body mass, varying from 46°C in yellow-plumed honeyeaters to 52°C in a single apostlebird, but was lower than that of three southern African ploceid passerines investigated previously. We argue this difference is functionally linked to a smaller scope for increases in EWL above baseline levels. Our data reiterate the reliance of passerines in general on respiratory evaporative heat loss via panting, but also reveal substantial within-order variation in heat tolerance and evaporative cooling capacity.

Authors+Show Affiliations

DST-NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa aemckechnie@zoology.up.ac.za.Department of Biology, University of Massachusetts, Amherst, MA 01003, USA.School of Animal & Veterinary Sciences, University of Adelaide, Roseworthy Campus, Roseworthy, SA 5371, Australia.UNM Biology Department, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA.UNM Biology Department, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA.UNM Biology Department, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA.

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

28455441

Citation

McKechnie, Andrew E., et al. "Avian Thermoregulation in the Heat: Evaporative Cooling in Five Australian Passerines Reveals Within-order Biogeographic Variation in Heat Tolerance." The Journal of Experimental Biology, vol. 220, no. Pt 13, 2017, pp. 2436-2444.
McKechnie AE, Gerson AR, McWhorter TJ, et al. Avian thermoregulation in the heat: evaporative cooling in five Australian passerines reveals within-order biogeographic variation in heat tolerance. J Exp Biol. 2017;220(Pt 13):2436-2444.
McKechnie, A. E., Gerson, A. R., McWhorter, T. J., Smith, E. K., Talbot, W. A., & Wolf, B. O. (2017). Avian thermoregulation in the heat: evaporative cooling in five Australian passerines reveals within-order biogeographic variation in heat tolerance. The Journal of Experimental Biology, 220(Pt 13), 2436-2444. https://doi.org/10.1242/jeb.155507
McKechnie AE, et al. Avian Thermoregulation in the Heat: Evaporative Cooling in Five Australian Passerines Reveals Within-order Biogeographic Variation in Heat Tolerance. J Exp Biol. 2017 07 1;220(Pt 13):2436-2444. PubMed PMID: 28455441.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Avian thermoregulation in the heat: evaporative cooling in five Australian passerines reveals within-order biogeographic variation in heat tolerance. AU - McKechnie,Andrew E, AU - Gerson,Alexander R, AU - McWhorter,Todd J, AU - Smith,Eric Krabbe, AU - Talbot,William A, AU - Wolf,Blair O, Y1 - 2017/04/28/ PY - 2016/12/26/received PY - 2017/04/20/accepted PY - 2017/4/30/pubmed PY - 2018/3/27/medline PY - 2017/4/30/entrez KW - Body temperature KW - Evaporative water loss KW - Hyperthermia KW - Passeriformes KW - Respiratory evaporative water loss KW - Resting metabolic rate SP - 2436 EP - 2444 JF - The Journal of experimental biology JO - J. Exp. Biol. VL - 220 IS - Pt 13 N2 - Evaporative heat loss pathways vary among avian orders, but the extent to which evaporative cooling capacity and heat tolerance vary within orders remains unclear. We quantified the upper limits to thermoregulation under extremely hot conditions in five Australian passerines: yellow-plumed honeyeater (Lichenostomus ornatus; ∼17 g), spiny-cheeked honeyeater (Acanthagenys rufogularis; ∼42 g), chestnut-crowned babbler (Pomatostomus ruficeps; ∼52 g), grey butcherbird (Cracticus torquatus; ∼86 g) and apostlebird (Struthidea cinerea; ∼118 g). At air temperatures (Ta) exceeding body temperature (Tb), all five species showed increases in Tb to maximum values around 44-45°C, accompanied by rapid increases in resting metabolic rate above clearly defined upper critical limits of thermoneutrality and increases in evaporative water loss (EWL) to levels equivalent to 670-860% of baseline rates at thermoneutral Ta Maximum cooling capacity, quantified as the fraction of metabolic heat production dissipated evaporatively, ranged from 1.20 to 2.17, consistent with the known range for passerines, and well below the corresponding ranges for columbids and caprimulgids. Heat tolerance limit (HTL, the maximum Ta tolerated) scaled positively with body mass, varying from 46°C in yellow-plumed honeyeaters to 52°C in a single apostlebird, but was lower than that of three southern African ploceid passerines investigated previously. We argue this difference is functionally linked to a smaller scope for increases in EWL above baseline levels. Our data reiterate the reliance of passerines in general on respiratory evaporative heat loss via panting, but also reveal substantial within-order variation in heat tolerance and evaporative cooling capacity. SN - 1477-9145 UR - https://www.unboundmedicine.com/medline/citation/28455441/Avian_thermoregulation_in_the_heat:_evaporative_cooling_in_five_Australian_passerines_reveals_within_order_biogeographic_variation_in_heat_tolerance_ L2 - http://jeb.biologists.org/cgi/pmidlookup?view=long&pmid=28455441 DB - PRIME DP - Unbound Medicine ER -