Avian thermoregulation in the heat: scaling of heat tolerance and evaporative cooling capacity in three southern African arid-zone passerines

Whitfield, Maxine C.; Smit, Ben; McKechnie, Andrew E.; Wolf, Blair O.

doi:10.1242/jeb.121749

Cited by 143 publications

(347 citation statements)

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“…The southern African component of the study took place at the same study sites and during the same periods as described by Whitfield et al (2015). We measured EWL, RMR and T b over a range of T a in three species from the family Columbidae, namely, Namaqua dove [Oena capensis (Linnaeus 1766), ∼40 g], laughing dove [Spilopelia senegalensis (Linnaeus 1766), ∼100 g; formerly Streptopelia senegalensis] and Cape turtle dove [Streptopelia capicola (Sundevall 1857), ∼153 g] (Hockey et al, 2005).…”

Section: Materials and Methods Study Sites And Speciesmentioning

confidence: 99%

“…Measurements of EWL, carbon dioxide production (VĊ O2 ), T a and T b were conducted using the same general methods and experimental setup as described by Whitfield et al (2015). Birds were placed individually in sealable plastic chambers with volumes of 4 litres (O. capensis) or 9 litres (S. senegalensis, S. capicola and Ocyphaps lophotes).…”

Section: Gas Exchange and Temperature Measurementsmentioning

confidence: 99%

“…Birds tended to remain calmer when flow rates were higher and chamber humidities were lower. As was the case in the study by Whitfield et al (2015), the high flow rates we used meant that fractional depletion of oxygen within the chamber was below the resolution of the oxygen analyzer we used (FC-10A, Sable Systems, Las Vegas, NV, USA), and oxygen consumption (VȮ 2 ) could therefore not be measured accurately. Core T b was measured during experiments using a temperature-sensitive passive integrated transponder (PIT) tag injected into the abdominal cavity of each bird, and a PIT tag reader and portable transceiver system, following Whitfield et al (2015).…”

Section: Gas Exchange and Temperature Measurementsmentioning

confidence: 99%

“…We used the same experimental protocol during which birds were exposed to progressively higher T a in a stepped profile as described by Whitfield et al (2015) and Smith et al (2015), and analyzed our data in the same way as in these studies. Birds were exposed to T a values of 25-40°C in 5°C increments, and T a values of 40-62°C in 2°C increments.…”

Section: Experimental Protocol and Data Analysesmentioning

confidence: 99%

“…The capacity for evaporative cooling is particularly pronounced in birds, reflecting their predominantly diurnal activity and limited use of thermally buffered underground microsites, even among species occupying the hottest regions on the planet (Dawson and Bartholomew, 1968;Dawson and Fisher, 1969;Dawson and Schmidt-Nielsen, 1964;Grant, 1982;Williams and Tieleman, 2005, but see also Williams and Tieleman, 2005). A number of studies have shown that birds can maintain T b 10-20°C below air temperature (T a ) during acute (Dawson and Fisher, 1969;Tieleman et al, 2002b;Whitfield et al, 2015;Wolf and Walsberg, 1996) and chronic (Marder and Arieli, 1988) heat exposure, via rapid increases in the rate of evaporative water loss (EWL) when T a exceeds normothermic T b . Under such conditions, a trade-off arises between the avoidance of hyperthermic T b and the avoidance of dehydration resulting from rapid depletion of body water; at T a values approaching 50°C, rates of EWL in very small birds may be equivalent to ∼7% of body mass per hour (Wolf and Walsberg, 1996).…”

Section: Introductionmentioning

confidence: 99%

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Avian thermoregulation in the heat: efficient evaporative cooling allows for extreme heat tolerance in four southern Hemisphere columbids

McKechnie

Whitfield

Smit

et al. 2016

Journal of Experimental Biology

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113

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Birds show phylogenetic variation in the relative importance of respiratory versus cutaneous evaporation, but the consequences for heat tolerance and evaporative cooling capacity remain unclear. We measured evaporative water loss (EWL), resting metabolic rate (RMR) and body temperature (T b ) in four arid-zone columbids from southern Africa [Namaqua dove (Oena capensis, ∼37 g), laughing dove (Spilopelia senegalensis, ∼89 g) and Cape turtle dove (Streptopelia capicola, ∼148 g)] and Australia [crested pigeon (Ocyphaps lophotes), ∼186 g] at air temperatures (T a ) of up to 62°C. There was no clear relationship between body mass and maximum T a tolerated during acute heat exposure. Maximum T b at very high T a was 43.1±1.0, 43.7±0.8, 44.7±0.3 and 44.3±0.8°C in Namaqua doves, laughing doves, Cape turtle doves and crested pigeons, respectively. In all four species, RMR increased significantly at T a above thermoneutrality, but the increases were relatively modest with RMR at T a =56°C being 32, 60, 99 and 11% higher, respectively, than at T a =35°C. At the highest T a values reached, evaporative heat loss was equivalent to 466, 227, 230 and 275% of metabolic heat production. The maximum ratio of evaporative heat loss to metabolic production observed in Namaqua doves, 4.66, exceeds by a substantial margin previous values reported for birds. Our results support the notion that cutaneous evaporation provides a highly efficient mechanism of heat dissipation and an enhanced ability to tolerate extremely high T a .

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Section: Materials and Methods Study Sites And Speciesmentioning

confidence: 99%

Section: Gas Exchange and Temperature Measurementsmentioning

confidence: 99%

Section: Gas Exchange and Temperature Measurementsmentioning

confidence: 99%

Section: Experimental Protocol and Data Analysesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Avian thermoregulation in the heat: efficient evaporative cooling allows for extreme heat tolerance in four southern Hemisphere columbids

McKechnie

Whitfield

Smit

et al. 2016

Journal of Experimental Biology

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113

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Limited heat tolerance in an Arctic passerine: Thermoregulatory implications for cold‐specialized birds in a rapidly warming world

O’Connor

Pogam

Young

et al. 2021

Ecology and Evolution

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Arctic animals inhabit some of the coldest environments on the planet and have evolved physiological mechanisms for minimizing heat loss under extreme cold. However, the Arctic is warming faster than the global average and how well Arctic animals tolerate even moderately high air temperatures (Ta) is unknown. Using flow‐through respirometry, we investigated the heat tolerance and evaporative cooling capacity of snow buntings (Plectrophenax nivalis; ≈31 g, N = 42), a cold specialist, Arctic songbird. We exposed buntings to increasing Ta and measured body temperature (Tb), resting metabolic rate (RMR), rates of evaporative water loss (EWL), and evaporative cooling efficiency (the ratio of evaporative heat loss to metabolic heat production). Buntings had an average (±SD) Tb of 41.3 ± 0.2°C at thermoneutral Ta and increased Tb to a maximum of 43.5 ± 0.3°C. Buntings started panting at Ta of 33.2 ± 1.7°C, with rapid increases in EWL starting at Ta = 34.6°C, meaning they experienced heat stress when air temperatures were well below their body temperature. Maximum rates of EWL were only 2.9× baseline rates at thermoneutral Ta, a markedly lower increase than seen in more heat‐tolerant arid‐zone species (e.g., ≥4.7× baseline rates). Heat‐stressed buntings also had low evaporative cooling efficiencies, with 95% of individuals unable to evaporatively dissipate an amount of heat equivalent to their own metabolic heat production. Our results suggest that buntings’ well‐developed cold tolerance may come at the cost of reduced heat tolerance. As the Arctic warms, and this and other species experience increased periods of heat stress, a limited capacity for evaporative cooling may force birds to increasingly rely on behavioral thermoregulation, such as minimizing activity, at the expense of diminished performance or reproductive investment.

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Simulated heat waves reduce cognitive and motor performance of an endotherm

Danner

Coomes

Derryberry

2021

Ecology and Evolution

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Heat waves cause mass mortality of animals, including humans, across the globe annually, which has drawn new attention to how animals cope with high air temperatures. Recent field research has explored behavioral responses to high air temperatures, which can influence reproductive success and mortality. Less well studied are the effects of high air temperatures on cognition, which may underlie behavioral changes. Specifically, it is poorly known if cognitive declines occur at high temperatures, and if cognitive and motor components of behavior are similarly affected. We tested how well zebra finches (Taeniopygia guttata castanotis), a model for cognition research, performed two learned foraging tasks (color association and detour‐reaching) at mild (22°C) and high (43 and 44°C) air temperatures that occur naturally in their range. We habituated birds to the trial conditions and temperatures on days preceding the test trials and at the trial temperature for 30 min immediately prior to each test trial. Trials lasted less than 10 min. At high air temperatures, zebra finches exhibited heat dissipation behaviors during most tasks, suggesting thermoregulatory challenge. Cognitive performance declined at high air temperatures in two of three measures: Color association was unaffected, but birds missed more food rewards, and did more unproductive behaviors. Motor performance declined at high temperatures on the color association task, including longer times to complete the task, move between food rewards, and process individual seeds. Performance declines varied among components of behavior and among individuals. We combined our behavioral data with existing climate data and predicted that in the austral summer of 2018–2019, zebra finches experienced air temperatures that caused cognitive and motor declines in our captive birds in 34% and 45% of their Australian range, respectively. This study provides novel experimental evidence that high air temperatures cause cognitive and motor performance decline in birds. Further, our results provide insights to how those declines might affect bird ecology and evolution. First, differences in declines among behavioral components may allow identification of behaviors that are most susceptible to decline in the wild. Second, variation in performance declines and heat dissipation behaviors among individuals suggests variability in heat tolerance, which could lead to differential fitness in the wild. Last, these results suggest that high air temperatures cause cognitive declines in the wild and that understanding cognition could help refine predictive models of population persistence.

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Avian thermoregulation in the heat: scaling of heat tolerance and evaporative cooling capacity in three southern African arid-zone passerines

Cited by 143 publications

References 48 publications

Avian thermoregulation in the heat: efficient evaporative cooling allows for extreme heat tolerance in four southern Hemisphere columbids

Avian thermoregulation in the heat: efficient evaporative cooling allows for extreme heat tolerance in four southern Hemisphere columbids

Limited heat tolerance in an Arctic passerine: Thermoregulatory implications for cold‐specialized birds in a rapidly warming world

Simulated heat waves reduce cognitive and motor performance of an endotherm

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