Heat dissipation behaviour of birds in seasonally hot arid‐zones: are there global patterns?
- Pattinson, Nicholas B, Thompson, Michelle L, Griego, Michael, Russell, Grace, Mitchell, Nicola J, Martin, Rowan O, Wolf, Blair O, Smit, Ben, Cunningham, Susan J, McKechnie, Andrew, Hockey, Philip A R
- Authors: Pattinson, Nicholas B , Thompson, Michelle L , Griego, Michael , Russell, Grace , Mitchell, Nicola J , Martin, Rowan O , Wolf, Blair O , Smit, Ben , Cunningham, Susan J , McKechnie, Andrew , Hockey, Philip A R
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441682 , vital:73906 , https://doi.org/10.1111/jav.02350
- Description: Quantifying organismal sensitivity to heat stress provides one means for predicting vulnerability to climate change. Birds are ideal for investigating this approach, as they display quantifiable fitness consequences associated with behavioural and physiological responses to heat stress. We used a recently developed method that examines correlations between readily‐observable behaviours and air temperature (Tair) to investigate interspecific variation in avian responses to heat stress in seasonally hot, arid regions on three continents: the southwestern United States, the Kalahari Desert of southern Africa and the Gascoyne region of western Australia.
- Full Text:
- Date Issued: 2020
- Authors: Pattinson, Nicholas B , Thompson, Michelle L , Griego, Michael , Russell, Grace , Mitchell, Nicola J , Martin, Rowan O , Wolf, Blair O , Smit, Ben , Cunningham, Susan J , McKechnie, Andrew , Hockey, Philip A R
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441682 , vital:73906 , https://doi.org/10.1111/jav.02350
- Description: Quantifying organismal sensitivity to heat stress provides one means for predicting vulnerability to climate change. Birds are ideal for investigating this approach, as they display quantifiable fitness consequences associated with behavioural and physiological responses to heat stress. We used a recently developed method that examines correlations between readily‐observable behaviours and air temperature (Tair) to investigate interspecific variation in avian responses to heat stress in seasonally hot, arid regions on three continents: the southwestern United States, the Kalahari Desert of southern Africa and the Gascoyne region of western Australia.
- Full Text:
- Date Issued: 2020
Regularly drinking desert birds have greater evaporative cooling capacity and higher heat tolerance limits than non‐drinking species
- Czenze, Zenon J, Kemp, Ryno, van Jaarsveld, Barry, Freeman, Marc T, Smit, Ben, Wolf, Blair O, McKechnie, Andrew
- Authors: Czenze, Zenon J , Kemp, Ryno , van Jaarsveld, Barry , Freeman, Marc T , Smit, Ben , Wolf, Blair O , McKechnie, Andrew
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441585 , vital:73900 , https://doi.org/10.1111/1365-2435.13573
- Description: Surface water is a critical resource for many birds inhabiting arid re-gions, but the implications of regular drinking and dependence on sur-face water for the evolution of thermal physiology remain largely unex-plored. We hypothesized that avian thermoregulation in the heat has evolved in tandem with the use of surface water and predicted that (a) regularly drinking species have a greater capacity to elevate rates of evaporative water loss (EWL) compared to non‐drinking species, and (b) heat tolerance limits (HTLs) are higher among drinking species. To test these predictions, we quantified thermoregulatory responses to high air temperature (Ta) in 12 species of passerines from the South African arid zone and combined these with values for an additional five species. We categorized each species as either: (a) water‐dependent, regularly drinking, or (b) water‐independent, occasional‐/non‐drinking.
- Full Text:
- Date Issued: 2020
- Authors: Czenze, Zenon J , Kemp, Ryno , van Jaarsveld, Barry , Freeman, Marc T , Smit, Ben , Wolf, Blair O , McKechnie, Andrew
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441585 , vital:73900 , https://doi.org/10.1111/1365-2435.13573
- Description: Surface water is a critical resource for many birds inhabiting arid re-gions, but the implications of regular drinking and dependence on sur-face water for the evolution of thermal physiology remain largely unex-plored. We hypothesized that avian thermoregulation in the heat has evolved in tandem with the use of surface water and predicted that (a) regularly drinking species have a greater capacity to elevate rates of evaporative water loss (EWL) compared to non‐drinking species, and (b) heat tolerance limits (HTLs) are higher among drinking species. To test these predictions, we quantified thermoregulatory responses to high air temperature (Ta) in 12 species of passerines from the South African arid zone and combined these with values for an additional five species. We categorized each species as either: (a) water‐dependent, regularly drinking, or (b) water‐independent, occasional‐/non‐drinking.
- Full Text:
- Date Issued: 2020
Differences in the use of surface water resources by desert birds are revealed using isotopic tracers
- Smit, Ben, Woodborne, Stephan, Wolf, Blair O, McKechnie, Andrew E
- Authors: Smit, Ben , Woodborne, Stephan , Wolf, Blair O , McKechnie, Andrew E
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440532 , vital:73790 , https://doi.org/10.1093/auk/uky005
- Description: The scarcity of free-standing water sources is a key determinant of animal and plant community structure in arid environments, and an understanding of the extent to which particular species use surface water is vital for modeling the effects of climate change on desert avifauna. We investigated interspecific variation in the use of artificial water sources among birds in the Kalahari Desert, South Africa, by (i) observations at waterholes and (ii) tracing spatial water-use patterns during summer by isotopically labeled water sources and blood sampling. More than 50% of the avian community (primarily insectivores and omnivores) were not observed to drink. The majority (53%) of species drinking at waterholes were granivorous, and their use of surface water was best predicted by their relative abundance in the community. Species representing the remaining dietary guilds drank significantly more on hot days. Blood samples revealed that only 11 of 42 species (mostly granivores and a few omnivores) showed evidence of drinking at a waterhole with enriched deuterium values; on average, in the latter birds, water from the enriched waterhole accounted for ~38% of their body water pool. These findings illustrate that 2 methods employed in this study provide different, but complementary data on the relative importance of a water source for an avian community. Although our results suggest that most avian species are independent of surface water, drinking patterns on the hottest days during our study period suggest that free-standing water might become more important for some of the non-drinking species under hotter climatic conditions.
- Full Text:
- Date Issued: 2019
- Authors: Smit, Ben , Woodborne, Stephan , Wolf, Blair O , McKechnie, Andrew E
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440532 , vital:73790 , https://doi.org/10.1093/auk/uky005
- Description: The scarcity of free-standing water sources is a key determinant of animal and plant community structure in arid environments, and an understanding of the extent to which particular species use surface water is vital for modeling the effects of climate change on desert avifauna. We investigated interspecific variation in the use of artificial water sources among birds in the Kalahari Desert, South Africa, by (i) observations at waterholes and (ii) tracing spatial water-use patterns during summer by isotopically labeled water sources and blood sampling. More than 50% of the avian community (primarily insectivores and omnivores) were not observed to drink. The majority (53%) of species drinking at waterholes were granivorous, and their use of surface water was best predicted by their relative abundance in the community. Species representing the remaining dietary guilds drank significantly more on hot days. Blood samples revealed that only 11 of 42 species (mostly granivores and a few omnivores) showed evidence of drinking at a waterhole with enriched deuterium values; on average, in the latter birds, water from the enriched waterhole accounted for ~38% of their body water pool. These findings illustrate that 2 methods employed in this study provide different, but complementary data on the relative importance of a water source for an avian community. Although our results suggest that most avian species are independent of surface water, drinking patterns on the hottest days during our study period suggest that free-standing water might become more important for some of the non-drinking species under hotter climatic conditions.
- Full Text:
- Date Issued: 2019
The functional significance of facultative hyperthermia varies with body size and phylogeny in birds
- Gerson, Alexander R, McKechnie, Andrew, Smit, Ben, Whitfield, Maxine C, Smith, Eric K, Talbot, William A, McWhorter, Todd J, Wolf, Blair O
- Authors: Gerson, Alexander R , McKechnie, Andrew , Smit, Ben , Whitfield, Maxine C , Smith, Eric K , Talbot, William A , McWhorter, Todd J , Wolf, Blair O
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441609 , vital:73901 , https://doi.org/10.1111/1365-2435.13274
- Description: Facultative hyperthermia, the elevation of body temperature above normothermic levels, during heat exposure, importantly affects the wa-ter economy and heat balance of terrestrial endotherms. We currently lack a mechanistic understanding of the benefits hyperthermia provides for avian taxa. Facultative hyperthermia has been proposed to minimize rates of water loss via three distinct mechanisms: M1) by maintaining body temperature (Tb) above environmental temperatures (Te), heat can be lost non‐evaporatively, saving water; M2) by minimizing the thermal gradient when Te > Tb, environmental heat gain and evaporative water loss rates are reduced; and M3) by storing heat via increases in Tb which reduces evaporative heat loss demands and conserves wa-ter. Although individuals may benefit from all three mechanisms during heat exposure, the relative importance of each mechanism has not been quantified among species that differ in their body size, heat toler-ance and mechanisms of evaporative heat dissipation. We measured resting metabolism, evaporative water loss and real‐time Tb from 33 species of birds representing nine orders ranging in mass from 8 to 300 g and estimated the water savings associated with each proposed mechanism. We show that facultative hyperthermia varies in its benefits among species.
- Full Text:
- Date Issued: 2019
The functional significance of facultative hyperthermia varies with body size and phylogeny in birds
- Authors: Gerson, Alexander R , McKechnie, Andrew , Smit, Ben , Whitfield, Maxine C , Smith, Eric K , Talbot, William A , McWhorter, Todd J , Wolf, Blair O
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441609 , vital:73901 , https://doi.org/10.1111/1365-2435.13274
- Description: Facultative hyperthermia, the elevation of body temperature above normothermic levels, during heat exposure, importantly affects the wa-ter economy and heat balance of terrestrial endotherms. We currently lack a mechanistic understanding of the benefits hyperthermia provides for avian taxa. Facultative hyperthermia has been proposed to minimize rates of water loss via three distinct mechanisms: M1) by maintaining body temperature (Tb) above environmental temperatures (Te), heat can be lost non‐evaporatively, saving water; M2) by minimizing the thermal gradient when Te > Tb, environmental heat gain and evaporative water loss rates are reduced; and M3) by storing heat via increases in Tb which reduces evaporative heat loss demands and conserves wa-ter. Although individuals may benefit from all three mechanisms during heat exposure, the relative importance of each mechanism has not been quantified among species that differ in their body size, heat toler-ance and mechanisms of evaporative heat dissipation. We measured resting metabolism, evaporative water loss and real‐time Tb from 33 species of birds representing nine orders ranging in mass from 8 to 300 g and estimated the water savings associated with each proposed mechanism. We show that facultative hyperthermia varies in its benefits among species.
- Full Text:
- Date Issued: 2019
Avian thermoregulation in the heat: is evaporative cooling more economical in nocturnal birds?
- O'Connor, Ryan S, Smit, Ben, Talbot, William A, Gerson, Alexander R, Brigham, R Mark, Wolf, Blair O, McKechnie, Andrew E
- Authors: O'Connor, Ryan S , Smit, Ben , Talbot, William A , Gerson, Alexander R , Brigham, R Mark , Wolf, Blair O , McKechnie, Andrew E
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441518 , vital:73895 , https://journals.biologists.com/jeb/article/221/17/jeb181420/19595/Avian-thermoregulation-in-the-heat-is-evaporative
- Description: Evaporative cooling is a prerequisite for avian occupancy of hot, arid environments, and is the only avenue of heat dissipation when air temperatures (Ta) exceed body temperature (Tb). Whereas diurnal birds can potentially rehydrate throughout the day, nocturnal species typically forgo drinking between sunrise and sunset. We hypothesized that nocturnal birds have evolved reduced rates of evaporative water loss (EWL) and more economical evaporative cooling mechanisms compared with diurnal species, permitting nocturnal species to tolerate extended periods of intense heat without becoming lethally dehydrated. We used phylogenetically informed regressions to compare EWL and evaporative cooling efficiency [ratio of evaporative heat loss (EHL) and metabolic heat production (MHP); EHL/MHP] among nocturnal and diurnal birds at high Ta. We analyzed variation in three response variables: (1) slope of EWL at Ta between 40 and 46°C, (2) EWL at Ta=46°C and (3) EHL/MHP at Ta=46°C. Nocturnality emerged as a weak, negative predictor, with nocturnal species having slightly shallower slopes and reduced EWL compared with diurnal species of similar mass.
- Full Text:
- Date Issued: 2018
- Authors: O'Connor, Ryan S , Smit, Ben , Talbot, William A , Gerson, Alexander R , Brigham, R Mark , Wolf, Blair O , McKechnie, Andrew E
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441518 , vital:73895 , https://journals.biologists.com/jeb/article/221/17/jeb181420/19595/Avian-thermoregulation-in-the-heat-is-evaporative
- Description: Evaporative cooling is a prerequisite for avian occupancy of hot, arid environments, and is the only avenue of heat dissipation when air temperatures (Ta) exceed body temperature (Tb). Whereas diurnal birds can potentially rehydrate throughout the day, nocturnal species typically forgo drinking between sunrise and sunset. We hypothesized that nocturnal birds have evolved reduced rates of evaporative water loss (EWL) and more economical evaporative cooling mechanisms compared with diurnal species, permitting nocturnal species to tolerate extended periods of intense heat without becoming lethally dehydrated. We used phylogenetically informed regressions to compare EWL and evaporative cooling efficiency [ratio of evaporative heat loss (EHL) and metabolic heat production (MHP); EHL/MHP] among nocturnal and diurnal birds at high Ta. We analyzed variation in three response variables: (1) slope of EWL at Ta between 40 and 46°C, (2) EWL at Ta=46°C and (3) EHL/MHP at Ta=46°C. Nocturnality emerged as a weak, negative predictor, with nocturnal species having slightly shallower slopes and reduced EWL compared with diurnal species of similar mass.
- Full Text:
- Date Issued: 2018
Avian thermoregulation in the heat: phylogenetic variation among avian orders in evaporative cooling capacity and heat tolerance
- Smit, Ben, Whitfield, Maxine C, Talbot, William A, Gerson, Alexander R, McKechnie, Andrew E, Wolf, Blair O
- Authors: Smit, Ben , Whitfield, Maxine C , Talbot, William A , Gerson, Alexander R , McKechnie, Andrew E , Wolf, Blair O
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440517 , vital:73789 , https://doi.org/10.1242/jeb.174870
- Description: Little is known about the phylogenetic variation of avian evaporative cooling efficiency and heat tolerance in hot environments. We quantified thermoregulatory responses to high air temperature (Ta) in ∼100-g representatives of three orders, namely, the African cuckoo (Cuculus gularis, Cuculiformes), lilac-breasted roller (Coracias caudatus, Coraciiformes) and Burchell's starling (Lamprotornis australis, Passeriformes). All three species initiated respiratory mechanisms to increase evaporative heat dissipation when body temperature (Tb) approached 41.5°C in response to increasing Ta, with gular flutter observed in cuckoos and panting in rollers and starlings. Resting metabolic rate and evaporative water loss increased by quantitatively similar magnitudes in all three species, although maximum rates of evaporative water loss were proportionately lower in starlings. Evaporative cooling efficiency [defined as the ratio of evaporative heat loss (EHL) to metabolic heat production (MHP)] generally remained below 2.0 in cuckoos and starlings, but reached a maximum of ∼3.5 in rollers. The high value for rollers reveals a very efficient evaporative cooling mechanism, and is similar to EHL/MHP maxima for similarly sized columbids which very effectively dissipate heat via cutaneous evaporation. This unexpected phylogenetic variation among the orders tested in the physiological mechanisms of heat dissipation is an important step toward determining the evolution of heat tolerance traits in desert birds.
- Full Text:
- Date Issued: 2018
- Authors: Smit, Ben , Whitfield, Maxine C , Talbot, William A , Gerson, Alexander R , McKechnie, Andrew E , Wolf, Blair O
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/440517 , vital:73789 , https://doi.org/10.1242/jeb.174870
- Description: Little is known about the phylogenetic variation of avian evaporative cooling efficiency and heat tolerance in hot environments. We quantified thermoregulatory responses to high air temperature (Ta) in ∼100-g representatives of three orders, namely, the African cuckoo (Cuculus gularis, Cuculiformes), lilac-breasted roller (Coracias caudatus, Coraciiformes) and Burchell's starling (Lamprotornis australis, Passeriformes). All three species initiated respiratory mechanisms to increase evaporative heat dissipation when body temperature (Tb) approached 41.5°C in response to increasing Ta, with gular flutter observed in cuckoos and panting in rollers and starlings. Resting metabolic rate and evaporative water loss increased by quantitatively similar magnitudes in all three species, although maximum rates of evaporative water loss were proportionately lower in starlings. Evaporative cooling efficiency [defined as the ratio of evaporative heat loss (EHL) to metabolic heat production (MHP)] generally remained below 2.0 in cuckoos and starlings, but reached a maximum of ∼3.5 in rollers. The high value for rollers reveals a very efficient evaporative cooling mechanism, and is similar to EHL/MHP maxima for similarly sized columbids which very effectively dissipate heat via cutaneous evaporation. This unexpected phylogenetic variation among the orders tested in the physiological mechanisms of heat dissipation is an important step toward determining the evolution of heat tolerance traits in desert birds.
- Full Text:
- Date Issued: 2018
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