Roost type influences torpor use by Australian owlet-nightjars

Lisa Doucette, R Brigham, C Pavey, F Geiser

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Australian owlet-nightjars (Aegotheles cristatus; ⿼50 g) are one of only a few avian species that roost in cavities year-round and regularly enter torpor. Cavity roosts act as thermal buffers, and roost type likely affects energy expenditure of small birds. We used radiotelemetry to locate diurnal winter roost sites of owlet-nightjars in central Australia and to measure body (Tb) and skin (Tskin) temperature. We also recorded ambient temperature inside (TIN) and outside roosts. Individual owlet-nightjars used one to seven different roosts (tracking time 3-10 weeks), selecting either rock crevices (four birds) or tree hollows (four birds), or switching between the two roost types (seven birds). Rock crevices (TIN +9°C to +33°C) were warmer and thermally more stable than tree hollows (TIN ⿿4.0°C to +37°C). Torpor, often expressed by a reduction of Tskin/Tb by >10°C for 3⿿4 h at dawn, was influenced by roost selection; torpor use in tree hollows was almost twice that in rock crevices. Despite the potential energy savings accrued from roosting in well-insulated cavities, owlet-nightjars roosted in tree hollows more often (65% bird days, n=398) than in rock crevices (35% bird days, n=211). Lower costs of arousal from torpor via passive rewarming and basking and decreased risk of predation are two possible explanations for the preference to roost in tree hollows. We provide the first evidence for the influence of cavity roost selection on torpor use in a free-ranging bird and show that roost selection and thermal biology are strongly interrelated in determining energy expenditure.
Original languageEnglish
Pages (from-to)845-854
Number of pages10
JournalNaturwissenschaften
Volume98
DOIs
Publication statusPublished - 2011
Externally publishedYes

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Torpor
torpor
resting periods
Birds
tree cavities
bird
birds
cavity
rocks
energy expenditure
rock
Energy Metabolism
Temperature
expenditure
skin
Hot Temperature
temperature
roost site
Body Weights and Measures
heat

Cite this

Doucette, Lisa ; Brigham, R ; Pavey, C ; Geiser, F. / Roost type influences torpor use by Australian owlet-nightjars. In: Naturwissenschaften. 2011 ; Vol. 98. pp. 845-854.
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title = "Roost type influences torpor use by Australian owlet-nightjars",
abstract = "Australian owlet-nightjars (Aegotheles cristatus; {\^a}¿¼50 g) are one of only a few avian species that roost in cavities year-round and regularly enter torpor. Cavity roosts act as thermal buffers, and roost type likely affects energy expenditure of small birds. We used radiotelemetry to locate diurnal winter roost sites of owlet-nightjars in central Australia and to measure body (Tb) and skin (Tskin) temperature. We also recorded ambient temperature inside (TIN) and outside roosts. Individual owlet-nightjars used one to seven different roosts (tracking time 3-10 weeks), selecting either rock crevices (four birds) or tree hollows (four birds), or switching between the two roost types (seven birds). Rock crevices (TIN +9{\^A}°C to +33{\^A}°C) were warmer and thermally more stable than tree hollows (TIN {\^a}¿¿4.0{\^A}°C to +37{\^A}°C). Torpor, often expressed by a reduction of Tskin/Tb by >10{\^A}°C for 3{\^a}¿¿4 h at dawn, was influenced by roost selection; torpor use in tree hollows was almost twice that in rock crevices. Despite the potential energy savings accrued from roosting in well-insulated cavities, owlet-nightjars roosted in tree hollows more often (65{\%} bird days, n=398) than in rock crevices (35{\%} bird days, n=211). Lower costs of arousal from torpor via passive rewarming and basking and decreased risk of predation are two possible explanations for the preference to roost in tree hollows. We provide the first evidence for the influence of cavity roost selection on torpor use in a free-ranging bird and show that roost selection and thermal biology are strongly interrelated in determining energy expenditure.",
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Roost type influences torpor use by Australian owlet-nightjars. / Doucette, Lisa; Brigham, R; Pavey, C; Geiser, F.

In: Naturwissenschaften, Vol. 98, 2011, p. 845-854.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Roost type influences torpor use by Australian owlet-nightjars

AU - Doucette, Lisa

AU - Brigham, R

AU - Pavey, C

AU - Geiser, F

PY - 2011

Y1 - 2011

N2 - Australian owlet-nightjars (Aegotheles cristatus; ⿼50 g) are one of only a few avian species that roost in cavities year-round and regularly enter torpor. Cavity roosts act as thermal buffers, and roost type likely affects energy expenditure of small birds. We used radiotelemetry to locate diurnal winter roost sites of owlet-nightjars in central Australia and to measure body (Tb) and skin (Tskin) temperature. We also recorded ambient temperature inside (TIN) and outside roosts. Individual owlet-nightjars used one to seven different roosts (tracking time 3-10 weeks), selecting either rock crevices (four birds) or tree hollows (four birds), or switching between the two roost types (seven birds). Rock crevices (TIN +9°C to +33°C) were warmer and thermally more stable than tree hollows (TIN ⿿4.0°C to +37°C). Torpor, often expressed by a reduction of Tskin/Tb by >10°C for 3⿿4 h at dawn, was influenced by roost selection; torpor use in tree hollows was almost twice that in rock crevices. Despite the potential energy savings accrued from roosting in well-insulated cavities, owlet-nightjars roosted in tree hollows more often (65% bird days, n=398) than in rock crevices (35% bird days, n=211). Lower costs of arousal from torpor via passive rewarming and basking and decreased risk of predation are two possible explanations for the preference to roost in tree hollows. We provide the first evidence for the influence of cavity roost selection on torpor use in a free-ranging bird and show that roost selection and thermal biology are strongly interrelated in determining energy expenditure.

AB - Australian owlet-nightjars (Aegotheles cristatus; ⿼50 g) are one of only a few avian species that roost in cavities year-round and regularly enter torpor. Cavity roosts act as thermal buffers, and roost type likely affects energy expenditure of small birds. We used radiotelemetry to locate diurnal winter roost sites of owlet-nightjars in central Australia and to measure body (Tb) and skin (Tskin) temperature. We also recorded ambient temperature inside (TIN) and outside roosts. Individual owlet-nightjars used one to seven different roosts (tracking time 3-10 weeks), selecting either rock crevices (four birds) or tree hollows (four birds), or switching between the two roost types (seven birds). Rock crevices (TIN +9°C to +33°C) were warmer and thermally more stable than tree hollows (TIN ⿿4.0°C to +37°C). Torpor, often expressed by a reduction of Tskin/Tb by >10°C for 3⿿4 h at dawn, was influenced by roost selection; torpor use in tree hollows was almost twice that in rock crevices. Despite the potential energy savings accrued from roosting in well-insulated cavities, owlet-nightjars roosted in tree hollows more often (65% bird days, n=398) than in rock crevices (35% bird days, n=211). Lower costs of arousal from torpor via passive rewarming and basking and decreased risk of predation are two possible explanations for the preference to roost in tree hollows. We provide the first evidence for the influence of cavity roost selection on torpor use in a free-ranging bird and show that roost selection and thermal biology are strongly interrelated in determining energy expenditure.

KW - Aegotheles

KW - Cavities

KW - Desert

KW - Roost selection

KW - Thermal buffering

KW - Thermoregulation.

U2 - 10.1007/s00114-011-0835-7

DO - 10.1007/s00114-011-0835-7

M3 - Article

VL - 98

SP - 845

EP - 854

JO - Die Naturwissenschaften

JF - Die Naturwissenschaften

SN - 0028-1042

ER -