Avian thermoregulation in the heat: metabolism, evaporative cooling and gular flutter in two small owls.

Autor: Talbot WA; Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA wtalbot@unm.edu., Gerson AR; Department of Biology, University of Massachusetts, Amherst, MA 01003, USA., Smith EK; Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA., McKechnie AE; 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., Wolf BO; Department of Biology, University of New Mexico, MSC03-2020, Albuquerque, NM 87131-0001, USA.
Jazyk: angličtina
Zdroj: The Journal of experimental biology [J Exp Biol] 2018 Jun 20; Vol. 221 (Pt 12). Date of Electronic Publication: 2018 Jun 20.
DOI: 10.1242/jeb.171108
Abstrakt: 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 ( T a ) and measured resting metabolic rate (RMR), evaporative water loss (EWL), body temperature ( T b ) and heat tolerance limits (HTL; the maximum T a reached). Comparatively low RMR values were observed in both species, T b approximated T a at 40°C and mild hyperthermia occurred as T a 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.
Competing Interests: Competing interestsThe authors declare no competing or financial interests.
(© 2018. Published by The Company of Biologists Ltd.)
Databáze: MEDLINE
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