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Avian thermoregulation in the heat: evaporative cooling capacity of arid-zone Caprimulgiformes from two continents.
J Exp Biol 2017; 220(Pt 19):3488-3498JE

Abstract

Birds in the order Caprimulgiformes (nightjars and allies) have a remarkable capacity for thermoregulation over a wide range of environmental temperatures, exhibiting pronounced heterothermy in cool conditions and extreme heat tolerance at high environmental temperatures. We measured thermoregulatory responses to acute heat stress in three species of Caprimulgiformes that nest in areas of extreme heat and aridity, the common poorwill (Phalaenoptilus nuttallii: Caprimulgidae) and lesser nighthawk (Chordeiles acutipennis: Caprimulgidae) in the Sonoran Desert of Arizona, and the Australian owlet-nightjar (Aegotheles cristatus: Aegothelidae) in the mallee woodlands of South Australia. We exposed wild-caught birds to progressively increasing air temperatures (Ta) and measured resting metabolic rate (RMR), evaporative water loss (EWL), body temperature (Tb) and heat tolerance limit (HTL; the maximum Ta reached). Comparatively low RMR values were observed in all species (0.35, 0.36 and 0.40 W for the poorwill, nighthawk and owlet-nightjar, respectively), with Tb approximating Ta at 40°C and mild hyperthermia occurring as Ta reached the HTL. Nighthawks and poorwills reached HTLs of 60 and 62°C, respectively, whereas the owlet-nightjar had a HTL of 52°C. RMR increased gradually above minima at Ta of 42, 42 and 35°C, and reached 1.7, 1.9 and 2.0 times minimum resting values at HTLs in the poorwill, nighthawk and owlet-nightjar, respectively. EWL increased rapidly and linearly as Ta exceeded Tb and resulted in maximum rates of evaporative heat dissipation equivalent to 237-424% of metabolic heat production. Bouts of gular flutter resulted in large transient increases in evaporative heat loss (50-123%) accompanied by only small increments in RMR (<5%). The cavity-nesting/roosting owlet-nightjar had a lower HTL and less efficient evaporative cooling compared with the species that nest and/or roost on open desert surfaces. The high efficiency of gular flutter for evaporative cooling, combined with mild hyperthermia, provides the physiological basis for defending Tb well below Ta in extreme heat and is comparable to the efficient cooling observed in arid-zone columbids in which cutaneous EWL is the predominant cooling pathway.

Authors+Show Affiliations

Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA wtalbot@unm.edu.School of Animal & Veterinary Sciences, University of Adelaide, Roseworthy Campus, SA 5371, Australia.Department of Biology, University of Massachusetts, Amherst, MA 01003, 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.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

28760832

Citation

Talbot, William A., et al. "Avian Thermoregulation in the Heat: Evaporative Cooling Capacity of Arid-zone Caprimulgiformes From Two Continents." The Journal of Experimental Biology, vol. 220, no. Pt 19, 2017, pp. 3488-3498.
Talbot WA, McWhorter TJ, Gerson AR, et al. Avian thermoregulation in the heat: evaporative cooling capacity of arid-zone Caprimulgiformes from two continents. J Exp Biol. 2017;220(Pt 19):3488-3498.
Talbot, W. A., McWhorter, T. J., Gerson, A. R., McKechnie, A. E., & Wolf, B. O. (2017). Avian thermoregulation in the heat: evaporative cooling capacity of arid-zone Caprimulgiformes from two continents. The Journal of Experimental Biology, 220(Pt 19), pp. 3488-3498. doi:10.1242/jeb.161653.
Talbot WA, et al. Avian Thermoregulation in the Heat: Evaporative Cooling Capacity of Arid-zone Caprimulgiformes From Two Continents. J Exp Biol. 2017 10 1;220(Pt 19):3488-3498. PubMed PMID: 28760832.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Avian thermoregulation in the heat: evaporative cooling capacity of arid-zone Caprimulgiformes from two continents. AU - Talbot,William A, AU - McWhorter,Todd J, AU - Gerson,Alexander R, AU - McKechnie,Andrew E, AU - Wolf,Blair O, Y1 - 2017/07/31/ PY - 2017/04/26/received PY - 2017/07/20/accepted PY - 2017/8/2/pubmed PY - 2018/5/15/medline PY - 2017/8/2/entrez KW - Caprimulgiformes KW - Evaporative water loss KW - Heat tolerance limit KW - Hyperthermia KW - Respirometry KW - Resting metabolic rate SP - 3488 EP - 3498 JF - The Journal of experimental biology JO - J. Exp. Biol. VL - 220 IS - Pt 19 N2 - Birds in the order Caprimulgiformes (nightjars and allies) have a remarkable capacity for thermoregulation over a wide range of environmental temperatures, exhibiting pronounced heterothermy in cool conditions and extreme heat tolerance at high environmental temperatures. We measured thermoregulatory responses to acute heat stress in three species of Caprimulgiformes that nest in areas of extreme heat and aridity, the common poorwill (Phalaenoptilus nuttallii: Caprimulgidae) and lesser nighthawk (Chordeiles acutipennis: Caprimulgidae) in the Sonoran Desert of Arizona, and the Australian owlet-nightjar (Aegotheles cristatus: Aegothelidae) in the mallee woodlands of South Australia. We exposed wild-caught birds to progressively increasing air temperatures (Ta) and measured resting metabolic rate (RMR), evaporative water loss (EWL), body temperature (Tb) and heat tolerance limit (HTL; the maximum Ta reached). Comparatively low RMR values were observed in all species (0.35, 0.36 and 0.40 W for the poorwill, nighthawk and owlet-nightjar, respectively), with Tb approximating Ta at 40°C and mild hyperthermia occurring as Ta reached the HTL. Nighthawks and poorwills reached HTLs of 60 and 62°C, respectively, whereas the owlet-nightjar had a HTL of 52°C. RMR increased gradually above minima at Ta of 42, 42 and 35°C, and reached 1.7, 1.9 and 2.0 times minimum resting values at HTLs in the poorwill, nighthawk and owlet-nightjar, respectively. EWL increased rapidly and linearly as Ta exceeded Tb and resulted in maximum rates of evaporative heat dissipation equivalent to 237-424% of metabolic heat production. Bouts of gular flutter resulted in large transient increases in evaporative heat loss (50-123%) accompanied by only small increments in RMR (<5%). The cavity-nesting/roosting owlet-nightjar had a lower HTL and less efficient evaporative cooling compared with the species that nest and/or roost on open desert surfaces. The high efficiency of gular flutter for evaporative cooling, combined with mild hyperthermia, provides the physiological basis for defending Tb well below Ta in extreme heat and is comparable to the efficient cooling observed in arid-zone columbids in which cutaneous EWL is the predominant cooling pathway. SN - 1477-9145 UR - https://www.unboundmedicine.com/medline/citation/28760832/Avian_thermoregulation_in_the_heat:_evaporative_cooling_capacity_of_arid_zone_Caprimulgiformes_from_two_continents_ L2 - http://jeb.biologists.org/cgi/pmidlookup?view=long&amp;pmid=28760832 DB - PRIME DP - Unbound Medicine ER -