Seasonal variation in thermal energetics of the Australian owlet-nightjar (Aegotheles cristatus)

Lisa Doucette, F Geiser

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19 Citations (Scopus)

Abstract

Many birds living in regions with seasonal fluctuations in ambient temperatures (Ta) typically respond to cold by increasing insulation and adjusting metabolic rate. Seasonal variation in thermal physiology has not been studied for the Caprimulgiformes, an order of birds that generally have basal metabolic rates (BMR) lower than predicted for their body mass. We measured the metabolic rate and thermal conductance of Australian owlet-nightjars (Aegotheles cristatus) during summer and winter using open-flow respirometry. Within the thermoneutral zone (TNZ; 31.3 to 34.8 °C), there was no seasonal difference in BMR or thermal conductance (C), but body temperature was higher in summer- (38.2±0.3 °C) than winter-acclimatized (37.1±0.5 °C) birds. Below the TNZ, resting metabolic rate (RMR) increased linearly with decreasing Ta, and RMR and C were higher for summer- than winter-acclimatized birds. The mean mass-specific BMR of owlet-nightjars (1.27 mL O2 g-1 h-1) was close to the allometrically predicted value for a 45 g Caprimulgiformes, but well below that predicted for birds overall. These results suggest that owlet-nightjars increase plumage insulation to cope with low winter Ta, which is reflected in the seasonal difference in RMR and C below the TNZ, rather than adjusting BMR.
Original languageEnglish
Pages (from-to)615-620
Number of pages6
JournalComparative biochemistry and physiology. Part A: Molecular integrative physiology
Volume151
DOIs
Publication statusPublished - 2008
Externally publishedYes

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Basal Metabolism
Birds
Hot Temperature
Insulation
Temperature
Physiology
Body Temperature

Cite this

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title = "Seasonal variation in thermal energetics of the Australian owlet-nightjar (Aegotheles cristatus)",
abstract = "Many birds living in regions with seasonal fluctuations in ambient temperatures (Ta) typically respond to cold by increasing insulation and adjusting metabolic rate. Seasonal variation in thermal physiology has not been studied for the Caprimulgiformes, an order of birds that generally have basal metabolic rates (BMR) lower than predicted for their body mass. We measured the metabolic rate and thermal conductance of Australian owlet-nightjars (Aegotheles cristatus) during summer and winter using open-flow respirometry. Within the thermoneutral zone (TNZ; 31.3 to 34.8 {\^A}°C), there was no seasonal difference in BMR or thermal conductance (C), but body temperature was higher in summer- (38.2{\^A}±0.3 {\^A}°C) than winter-acclimatized (37.1{\^A}±0.5 {\^A}°C) birds. Below the TNZ, resting metabolic rate (RMR) increased linearly with decreasing Ta, and RMR and C were higher for summer- than winter-acclimatized birds. The mean mass-specific BMR of owlet-nightjars (1.27 mL O2 g-1 h-1) was close to the allometrically predicted value for a 45 g Caprimulgiformes, but well below that predicted for birds overall. These results suggest that owlet-nightjars increase plumage insulation to cope with low winter Ta, which is reflected in the seasonal difference in RMR and C below the TNZ, rather than adjusting BMR.",
keywords = "Caprimulgiformes, Conductance, Energetic costs, Insulation, Metabolic rate, Moulting, Respirometry, Seasonal acclimatization",
author = "Lisa Doucette and F Geiser",
year = "2008",
doi = "10.1016/j.cbpa.2008.07.025",
language = "English",
volume = "151",
pages = "615--620",
journal = "Comparative biochemistry and physiology. Part A, Molecular & integrative physiology",
issn = "1095-6433",
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T1 - Seasonal variation in thermal energetics of the Australian owlet-nightjar (Aegotheles cristatus)

AU - Doucette, Lisa

AU - Geiser, F

PY - 2008

Y1 - 2008

N2 - Many birds living in regions with seasonal fluctuations in ambient temperatures (Ta) typically respond to cold by increasing insulation and adjusting metabolic rate. Seasonal variation in thermal physiology has not been studied for the Caprimulgiformes, an order of birds that generally have basal metabolic rates (BMR) lower than predicted for their body mass. We measured the metabolic rate and thermal conductance of Australian owlet-nightjars (Aegotheles cristatus) during summer and winter using open-flow respirometry. Within the thermoneutral zone (TNZ; 31.3 to 34.8 °C), there was no seasonal difference in BMR or thermal conductance (C), but body temperature was higher in summer- (38.2±0.3 °C) than winter-acclimatized (37.1±0.5 °C) birds. Below the TNZ, resting metabolic rate (RMR) increased linearly with decreasing Ta, and RMR and C were higher for summer- than winter-acclimatized birds. The mean mass-specific BMR of owlet-nightjars (1.27 mL O2 g-1 h-1) was close to the allometrically predicted value for a 45 g Caprimulgiformes, but well below that predicted for birds overall. These results suggest that owlet-nightjars increase plumage insulation to cope with low winter Ta, which is reflected in the seasonal difference in RMR and C below the TNZ, rather than adjusting BMR.

AB - Many birds living in regions with seasonal fluctuations in ambient temperatures (Ta) typically respond to cold by increasing insulation and adjusting metabolic rate. Seasonal variation in thermal physiology has not been studied for the Caprimulgiformes, an order of birds that generally have basal metabolic rates (BMR) lower than predicted for their body mass. We measured the metabolic rate and thermal conductance of Australian owlet-nightjars (Aegotheles cristatus) during summer and winter using open-flow respirometry. Within the thermoneutral zone (TNZ; 31.3 to 34.8 °C), there was no seasonal difference in BMR or thermal conductance (C), but body temperature was higher in summer- (38.2±0.3 °C) than winter-acclimatized (37.1±0.5 °C) birds. Below the TNZ, resting metabolic rate (RMR) increased linearly with decreasing Ta, and RMR and C were higher for summer- than winter-acclimatized birds. The mean mass-specific BMR of owlet-nightjars (1.27 mL O2 g-1 h-1) was close to the allometrically predicted value for a 45 g Caprimulgiformes, but well below that predicted for birds overall. These results suggest that owlet-nightjars increase plumage insulation to cope with low winter Ta, which is reflected in the seasonal difference in RMR and C below the TNZ, rather than adjusting BMR.

KW - Caprimulgiformes

KW - Conductance

KW - Energetic costs

KW - Insulation

KW - Metabolic rate

KW - Moulting

KW - Respirometry

KW - Seasonal acclimatization

U2 - 10.1016/j.cbpa.2008.07.025

DO - 10.1016/j.cbpa.2008.07.025

M3 - Article

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SP - 615

EP - 620

JO - Comparative biochemistry and physiology. Part A, Molecular & integrative physiology

JF - Comparative biochemistry and physiology. Part A, Molecular & integrative physiology

SN - 1095-6433

ER -