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Avian thermoregulation in the heat: metabolism, evaporative cooling and gular flutter in two small owls.
J Exp Biol 2018; 221(Pt 12)JE

Abstract

The thermoregulatory responses of owls to heat stress have been the subject of few studies. Although nocturnality buffers desert-dwelling owls from significant heat stress during activity, roost sites in tree and cactus cavities or in deep shade provide only limited refuge from high environmental temperatures during the day. We measured thermoregulatory responses to acute heat stress in two species of small owls, the elf owl (Micrathene whitneyi) and the western screech-owl (Megascops kennicottii), which occupy the Sonoran Desert of southwestern North America, an area of extreme heat and aridity. 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 limits (HTL; the maximum Ta reached). Comparatively low RMR values were observed in both species, Tb approximated Ta at 40°C and mild hyperthermia occurred as Ta was increased toward the HTL. Elf owls and screech-owls reached HTLs of 48 and 52°C, respectively, and RMR increased to 1.5 and 1.9 times thermoneutral values. Rates of EWL at the HTL allowed for the dissipation of 167-198% of metabolic heat production (MHP). Gular flutter was used as the primary means of evaporative heat dissipation and produced large increases in evaporative heat loss (44-100%), accompanied by only small increases (<5%) in RMR. These small, cavity-nesting owls have thermoregulatory capacities that are intermediate between those of the open-ground nesting nightjars and the passerines that occupy the same ecosystem.

Authors+Show Affiliations

Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA wtalbot@unm.edu.Department of Biology, University of Massachusetts, Amherst, MA 01003, 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.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

29925545

Citation

Talbot, William A., et al. "Avian Thermoregulation in the Heat: Metabolism, Evaporative Cooling and Gular Flutter in Two Small Owls." The Journal of Experimental Biology, vol. 221, no. Pt 12, 2018.
Talbot WA, Gerson AR, Smith EK, et al. Avian thermoregulation in the heat: metabolism, evaporative cooling and gular flutter in two small owls. J Exp Biol. 2018;221(Pt 12).
Talbot, W. A., Gerson, A. R., Smith, E. K., McKechnie, A. E., & Wolf, B. O. (2018). Avian thermoregulation in the heat: metabolism, evaporative cooling and gular flutter in two small owls. The Journal of Experimental Biology, 221(Pt 12), doi:10.1242/jeb.171108.
Talbot WA, et al. Avian Thermoregulation in the Heat: Metabolism, Evaporative Cooling and Gular Flutter in Two Small Owls. J Exp Biol. 2018 06 20;221(Pt 12) PubMed PMID: 29925545.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Avian thermoregulation in the heat: metabolism, evaporative cooling and gular flutter in two small owls. AU - Talbot,William A, AU - Gerson,Alexander R, AU - Smith,Eric Krabbe, AU - McKechnie,Andrew E, AU - Wolf,Blair O, Y1 - 2018/06/20/ PY - 2017/09/25/received PY - 2018/04/17/accepted PY - 2018/6/22/entrez PY - 2018/6/22/pubmed PY - 2019/10/8/medline KW - Body temperature KW - Evaporative water loss KW - Heat tolerance limit KW - Respirometry KW - Resting metabolic rate KW - Strigiformes JF - The Journal of experimental biology JO - J. Exp. Biol. VL - 221 IS - Pt 12 N2 - The thermoregulatory responses of owls to heat stress have been the subject of few studies. Although nocturnality buffers desert-dwelling owls from significant heat stress during activity, roost sites in tree and cactus cavities or in deep shade provide only limited refuge from high environmental temperatures during the day. We measured thermoregulatory responses to acute heat stress in two species of small owls, the elf owl (Micrathene whitneyi) and the western screech-owl (Megascops kennicottii), which occupy the Sonoran Desert of southwestern North America, an area of extreme heat and aridity. 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 limits (HTL; the maximum Ta reached). Comparatively low RMR values were observed in both species, Tb approximated Ta at 40°C and mild hyperthermia occurred as Ta was increased toward the HTL. Elf owls and screech-owls reached HTLs of 48 and 52°C, respectively, and RMR increased to 1.5 and 1.9 times thermoneutral values. Rates of EWL at the HTL allowed for the dissipation of 167-198% of metabolic heat production (MHP). Gular flutter was used as the primary means of evaporative heat dissipation and produced large increases in evaporative heat loss (44-100%), accompanied by only small increases (<5%) in RMR. These small, cavity-nesting owls have thermoregulatory capacities that are intermediate between those of the open-ground nesting nightjars and the passerines that occupy the same ecosystem. SN - 1477-9145 UR - https://www.unboundmedicine.com/medline/citation/29925545/Avian_thermoregulation_in_the_heat:_metabolism_evaporative_cooling_and_gular_flutter_in_two_small_owls_ L2 - http://jeb.biologists.org/cgi/pmidlookup?view=long&amp;pmid=29925545 DB - PRIME DP - Unbound Medicine ER -