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Avian thermoregulation in the heat: evaporative cooling capacity and thermal tolerance in two Australian parrots.
J Exp Biol. 2018 03 23; 221(Pt 6)JE

Abstract

Avian orders differ in their thermoregulatory capabilities and tolerance of high environmental temperatures. Evaporative heat loss, and the primary avenue whereby it occurs, differs amongst taxa. Although Australian parrots (Psittaciformes) have been impacted by mass mortality events associated with extreme weather events (heat waves), their thermoregulatory physiology has not been well characterized. We quantified the upper limits to thermoregulation under extremely hot conditions in two Australian parrots: the mulga parrot (Psephotellus varius; ∼55 g) and the galah (Eolophus roseicapilla; ∼265 g). At air temperatures (Ta) exceeding body temperature (Tb), both species showed increases in Tb to maximum values around 43-44°C, accompanied by rapid increases in resting metabolic rate above clearly defined upper critical limits of thermoneutrality and increases in evaporative water loss to levels equivalent to 700-1000% of baseline rates at thermoneutral Ta Maximum cooling capacity, quantified as the fraction of metabolic heat production dissipated evaporatively, ranged from 1.71 to 1.79, consistent with the known range for parrots, similar to the corresponding range in passerines, and well below the corresponding ranges for columbids and caprimulgids. Heat tolerance limit (the maximum Ta tolerated) ranged from 44 to 55°C, similar to the range reported for passerines, but lower than that reported for columbids and caprimulgids. Our data suggest that heat tolerance in parrots is similar to that in passerines. We argue that understanding how thermoregulatory capacity and heat tolerance vary across avian orders is vital for predicting how climate change and the associated increase in frequency of extreme weather events may impact avian populations in the future.

Authors+Show Affiliations

School of Animal & Veterinary Sciences, University of Adelaide, Roseworthy Campus, South Australia 5371, Australia todd.mcwhorter@adelaide.edu.au.Department of Biology, University of Massachusetts, Amherst, MA 01003, USA.Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA.Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA.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. South African Research Chair in Conservation Physiology, National Zoological Gardens of South Africa, P.O. Box 754, Pretoria 0001, South Africa.Department of Biology, 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

29440360

Citation

McWhorter, Todd J., et al. "Avian Thermoregulation in the Heat: Evaporative Cooling Capacity and Thermal Tolerance in Two Australian Parrots." The Journal of Experimental Biology, vol. 221, no. Pt 6, 2018.
McWhorter TJ, Gerson AR, Talbot WA, et al. Avian thermoregulation in the heat: evaporative cooling capacity and thermal tolerance in two Australian parrots. J Exp Biol. 2018;221(Pt 6).
McWhorter, T. J., Gerson, A. R., Talbot, W. A., Smith, E. K., McKechnie, A. E., & Wolf, B. O. (2018). Avian thermoregulation in the heat: evaporative cooling capacity and thermal tolerance in two Australian parrots. The Journal of Experimental Biology, 221(Pt 6). https://doi.org/10.1242/jeb.168930
McWhorter TJ, et al. Avian Thermoregulation in the Heat: Evaporative Cooling Capacity and Thermal Tolerance in Two Australian Parrots. J Exp Biol. 2018 03 23;221(Pt 6) PubMed PMID: 29440360.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Avian thermoregulation in the heat: evaporative cooling capacity and thermal tolerance in two Australian parrots. AU - McWhorter,Todd J, AU - Gerson,Alexander R, AU - Talbot,William A, AU - Smith,Eric Krabbe, AU - McKechnie,Andrew E, AU - Wolf,Blair O, Y1 - 2018/03/23/ PY - 2017/08/25/received PY - 2018/02/01/accepted PY - 2018/2/15/pubmed PY - 2019/4/4/medline PY - 2018/2/15/entrez KW - Body temperature KW - Evaporative water loss KW - Hyperthermia KW - Psittaciformes KW - Respiratory evaporative water loss KW - Resting metabolic rate JF - The Journal of experimental biology JO - J. Exp. Biol. VL - 221 IS - Pt 6 N2 - Avian orders differ in their thermoregulatory capabilities and tolerance of high environmental temperatures. Evaporative heat loss, and the primary avenue whereby it occurs, differs amongst taxa. Although Australian parrots (Psittaciformes) have been impacted by mass mortality events associated with extreme weather events (heat waves), their thermoregulatory physiology has not been well characterized. We quantified the upper limits to thermoregulation under extremely hot conditions in two Australian parrots: the mulga parrot (Psephotellus varius; ∼55 g) and the galah (Eolophus roseicapilla; ∼265 g). At air temperatures (Ta) exceeding body temperature (Tb), both species showed increases in Tb to maximum values around 43-44°C, accompanied by rapid increases in resting metabolic rate above clearly defined upper critical limits of thermoneutrality and increases in evaporative water loss to levels equivalent to 700-1000% of baseline rates at thermoneutral Ta Maximum cooling capacity, quantified as the fraction of metabolic heat production dissipated evaporatively, ranged from 1.71 to 1.79, consistent with the known range for parrots, similar to the corresponding range in passerines, and well below the corresponding ranges for columbids and caprimulgids. Heat tolerance limit (the maximum Ta tolerated) ranged from 44 to 55°C, similar to the range reported for passerines, but lower than that reported for columbids and caprimulgids. Our data suggest that heat tolerance in parrots is similar to that in passerines. We argue that understanding how thermoregulatory capacity and heat tolerance vary across avian orders is vital for predicting how climate change and the associated increase in frequency of extreme weather events may impact avian populations in the future. SN - 1477-9145 UR - https://www.unboundmedicine.com/medline/citation/29440360/Avian_thermoregulation_in_the_heat:_evaporative_cooling_capacity_and_thermal_tolerance_in_two_Australian_parrots_ L2 - http://jeb.biologists.org/cgi/pmidlookup?view=long&pmid=29440360 DB - PRIME DP - Unbound Medicine ER -