THE COOLING POWER OF THE PIGEON HEAD

1994 ◽  
Vol 194 (1) ◽  
pp. 329-339 ◽  
Author(s):  
R St-Laurent ◽  
J Larochelle
Keyword(s):  
Wind Speed ◽  
Heat Dissipation ◽  
Buccal Cavity ◽  
Resting Metabolic Rate ◽  
Cooling Power ◽  
Evaporative Heat Loss ◽  
Body Temperatures ◽  
Air Stream ◽  
Beak Opening ◽  
Stable Core

Resting pigeons preheated to a stable core temperature of 43.2 °C, which is within the range of body temperatures recorded during flight, were able to cool their body at high rates if their head and upper neck were exposed to an air stream at 23.5 °C. The heat dissipation capacity of the head and neck, estimated from measurements made at a wind speed (100 km h-1) corresponding to fast flight, was 9.8 W, or 4.5 times the resting heat production. Since the greater part of this capacity, about 8 W, was attributable to the inner surfaces of the mouth, ram ventilation of the buccal cavity appears to be an important mechanism for increasing evaporative heat loss during flight. Accordingly, wind-assisted mouth cooling should be utilized by resting pigeons, since exposure to a slight breeze (approximately 10 km h-1) could augment their dissipating power by an amount equivalent to their resting metabolic rate. It is concluded that beak opening, together with a source of convection other than panting and gular flutter, is required to exploit fully the heat dissipation capacity of the buccopharyngeal mucosa of birds.

scholarly journals Thermoregulation in desert birds: scaling and phylogenetic variation in heat tolerance and evaporative cooling

2021 ◽  
Vol 224 (Suppl 1) ◽  
pp. jeb229211
Author(s):  
Andrew E. McKechnie ◽  
Alexander R. Gerson ◽  
Blair O. Wolf
Keyword(s):  
Heat Tolerance ◽  
Heat Dissipation ◽  
Arid Zone ◽  
Resting Metabolic Rate ◽  
Heat Exposure ◽  
Published Data ◽  
Evaporative Heat Loss ◽  
Evaporative Water ◽  
Data Set ◽  
The Difference

ABSTRACTEvaporative heat dissipation is a key aspect of avian thermoregulation in hot environments. We quantified variation in avian thermoregulatory performance at high air temperatures (Ta) using published data on body temperature (Tb), evaporative water loss (EWL) and resting metabolic rate (RMR) measured under standardized conditions of very low humidity in 56 arid-zone species. Maximum Tb during acute heat exposure varied from 42.5±1.3°C in caprimulgids to 44.5±0.5°C in passerines. Among passerines, both maximum Tb and the difference between maximum and normothermic Tb decreased significantly with body mass (Mb). Scaling exponents for minimum thermoneutral EWL and maximum EWL were 0.825 and 0.801, respectively, even though evaporative scope (ratio of maximum to minimum EWL) varied widely among species. Upper critical limits of thermoneutrality (Tuc) varied by >20°C and maximum RMR during acute heat exposure scaled to Mb0.75 in both the overall data set and among passerines. The slope of RMR at Ta>Tuc increased significantly with Mb but was substantially higher among passerines, which rely on panting, compared with columbids, in which cutaneous evaporation predominates. Our analysis supports recent arguments that interspecific within-taxon variation in heat tolerance is functionally linked to evaporative scope and maximum ratios of evaporative heat loss (EHL) to metabolic heat production (MHP). We provide predictive equations for most variables related to avian heat tolerance. Metabolic costs of heat dissipation pathways, rather than capacity to increase EWL above baseline levels, appear to represent the major constraint on the upper limits of avian heat tolerance.

scholarly journals Avian thermoregulation in the heat: phylogenetic variation among avian orders in evaporative cooling capacity and heat tolerance

2017 ◽  
Author(s):  
Ben Smit ◽  
Maxine C. Whitfield ◽  
William A. Talbot ◽  
Alexander R. Gerson ◽  
Andrew E. McKechnie ◽  
...  
Keyword(s):  
Heat Tolerance ◽  
Heat Dissipation ◽  
Resting Metabolic Rate ◽  
Evaporative Cooling ◽  
Cooling Capacity ◽  
Evaporative Heat Loss ◽  
Cooling Efficiency ◽  
Evaporative Water ◽  
Cutaneous Evaporation ◽  
Hot Environments

AbstractLittle 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: 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 (RMR) and evaporative water loss (EWL) increased by quantitatively similar magnitudes in all three species, although maximum rates of EWL 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.Summary statementWe show that avian evaporative cooling efficiency and heat tolerance display substantial taxonomic variation that are, unexpectedly, not systematically related to the use of panting versus gular flutter processes.

The Cooling Power of Pigeon Wings

1991 ◽  
Vol 155 (1) ◽  
pp. 193-202 ◽  
Author(s):  
ALBERT CRAIG ◽  
JACQUES LAROCHELLE
Keyword(s):  
Body Temperature ◽  
Heat Production ◽  
Heat Dissipation ◽  
Experimental System ◽  
Whole Body ◽  
Cooling Power ◽  
Wind Speeds ◽  
Maximum Value ◽  
Body Cooling ◽  
Whole Body Cooling

The rate of heat loss through the stretched wings (Hwings) was studied in resting pigeons preheated to a body temperature (43.7°C) within the range of those recorded during flight. The experimental system was designed to allow the calculation of Hwings from the increase in whole-body cooling rates resulting from exposure of the wings to various wind speeds (0–50 km h−1) at 23°C. The maximum value of HWings was 3.8 W, less than twice the heat production of a resting pigeon. This indicates that the contribution of the wings to heat dissipation during flight may not be nearly as important as has been supposed. At low windspeeds (0–12.5 km h−1), HWings corresponded to about 40% of the resting rate of heat production, and this value is discussed in connection with the various wing postures observed in hyperthermic birds.

Effect of heating rate on evaporative heat loss in the microwave-exposed mouse

1982 ◽  
Vol 53 (2) ◽  
pp. 316-323 ◽  
Author(s):  
C. J. Gordon
Keyword(s):  
Body Temperature ◽  
Heat Loss ◽  
Heat Dissipation ◽  
Dew Point ◽  
Whole Body ◽  
Evaporative Heat Loss ◽  
Heat Absorption ◽  
Deep Body Temperature ◽  
The Difference ◽  
Body Heat

Male CBA/J mice were administered heat loads of 0–28 J X g-1 at specific absorption rates (SARs) of either 47 or 93 W X kg-1 by exposure to 2,450-MHz microwave radiation at an ambient temperature of 30 degrees C while evaporative heat loss (EHL) was continuously monitored with dew-point hygrometry. At an SAR of 47 W X kg-1 a threshold heat load of 10.5 J X g-1 had to be exceeded before EHL increased. An approximate doubling of SAR to 93 W X kg-1 reduced the threshold to 5.2 J X g-1. Above threshold the slopes of the regression lines were 1.15 and 0.929 for the low- and high-SAR groups, respectively. Thus the difference in threshold and not slope attributes to the significant increase in EHL when mice are exposed at a high SAR (P less than 0.02). In separate experiments a SAR of 47 W X kg-1 raised the deep body temperature of anesthetized mice at a rate of 0.026 degrees C X s-1, whereas 93 W X kg-1 raised temperature at 0.049 degrees C X s-1. Hence the sensitivity of the EHL mode of heat dissipation is directly proportional to the rate of heat absorption and to the rate of rise in body temperature. These data contradict the notion that mammals have control over whole-body heat exchange only (i.e., thermoregulation) but instead indicate that the EHL system is highly responsive to the rate of heat absorption (i.e., temperature regulation).

scholarly journals Testing the heat dissipation limit theory in a breeding passerine

2018 ◽  
Vol 285 (1878) ◽  
pp. 20180652 ◽  
Author(s):  
Jan-Åke Nilsson ◽  
Andreas Nord
Keyword(s):  
Heat Dissipation ◽  
Work Rate ◽  
Body Temperatures ◽  
Limit Theory ◽  
Ambient Temperatures ◽  
Metabolic Heat ◽  
Thermal Window ◽  
Future Reproduction ◽  
Maximum Work ◽  
Males And Females

The maximum work rate of animals has recently been suggested to be determined by the rate at which excess metabolic heat generated during work can be dissipated (heat dissipation limitation (HDL) theory). As a first step towards testing this theory in wild animals, we experimentally manipulated brood size in breeding marsh tits ( Poecile palustris ) to change their work rate. Parents feeding nestlings generally operated at above-normal body temperatures. Body temperature in both males and females increased with maximum ambient temperature and with manipulated work rate, sometimes even exceeding 45°C, which is close to suggested lethal levels for birds. Such high body temperatures have previously only been described for birds living in hot and arid regions. Thus, reproductive effort in marsh tits may potentially be limited by the rate of heat dissipation. Females had lower body temperatures, a possible consequence of their brood patch serving as a thermal window facilitating heat dissipation. Because increasing body temperatures are connected to somatic costs, we suggest that the HDL theory may constitute a possible mediator of the trade-off between current and future reproduction. It follows that globally increasing, more stochastic, ambient temperatures may restrict the capacity for sustained work of animals in the future.

The significance of coat type in cattle

1960 ◽  
Vol 11 (4) ◽  
pp. 645 ◽  
Author(s):  
HG Turner ◽  
AV Schleger
Keyword(s):  
Growth Rate ◽  
Body Weight ◽  
Beef Cattle ◽  
Heat Dissipation ◽  
Metabolic Efficiency ◽  
Body Temperatures ◽  
Potential Value ◽  
Respiration Rates ◽  
Different Seasons ◽  
Age And Sex

A system of subjective scoring of cattle coats, ranging from very sleek to very woolly, is described. It has been applied to about 1600 animals, of which 500 were Hereford and Shorthorn cows and the rest their progeny from matings in four years to British breed and Zebu bulls. Consistency of scoring within and between observers is satisfactory. Highly significant differences between animals of the same breed persist through different seasons. The repeatability of coat score is 0.6 or more over intervals of up to 17 months. Effects of season, age, and sex are described. Heritability of coat score is estimated at 0.63. Coat scores are well correlated with body temperatures and respiration rates. Coat score and post-weaning growth rate of British breed calves are correlated to such a degree that coat score can be superior to a record of body weight as an estimate of growth capacity. The genetic correlation between coat score and growth rate is high in the British breeds. Evidence of the relation between coat score and growth rate in Zebu cross calves is inconclusive. The observed relationships are discussed with particular reference to their physiological causes. The results indicate the potential value of coat characters in selecting tropical beef cattle. The degree to which these results may be applicable to other populations in other environments is discussed. It is concluded that a sleek coat is important in favouring heat dissipation, but it may have even greater significance as an indicator of metabolic efficiency or of capacity to react favourably to stress.

Characteristics of Heat Dissipation from a Block Heat Source Module in a Three-Dimensional Cabinet to Ambient Natural Convective Air Stream

2012 ◽  
Vol 229-231 ◽  
pp. 2589-2592
Author(s):  
Y.L. Tsay ◽  
J.C. Cheng
Keyword(s):  
Natural Convection ◽  
Rayleigh Number ◽  
Heat Source ◽  
Heat Dissipation ◽  
Three Dimensional ◽  
Thermal Interaction ◽  
Air Stream ◽  
Conjugate Conduction ◽  
Air Streams ◽  
Thermal Conductivities

This study combined the numerical analysis and experimental measurement to investigate the conjugate conduction and natural convection for a block heat source module in a three-dimensional cabinet filled and surrounded by air. The effects of Rayleigh number Ra, module position C1, ratio of block to air thermal conductivities Kbf, and ratio of board to air thermal conductivities Kpf are examined. Moreover, efforts are carried out to explore the influence of thermal interaction between the air streams inside and outside the cabinet.

scholarly journals Cooling Effect Efficiency Prediction of Aluminum Dimples Block using DOE Technique

2018 ◽  
Vol 7 (4.30) ◽  
pp. 152
Author(s):  
Ganesan H. N ◽  
Kasim M. S ◽  
Izamshah R ◽  
Anand T.J. S ◽  
Hafiz M. S. A ◽  
...  
Keyword(s):  
Heat Dissipation ◽  
Orientation Angle ◽  
Cooling Time ◽  
Cooling Effect ◽  
Average Error ◽  
Stream Velocity ◽  
Air Stream ◽  
Enhancement Method ◽  
Air Flow Velocity ◽  
The Mathematical Model

The main aim of the present work is to study the effect of heat enhancement method on the cooling process of a spherical dimple profile. It was prominently known that introducing dimples configuration causes an enhancement in heat transfer over a surface. In this project, an experimental investigation was carried out to examine the cooling effect of the spherical dimple profile during steady laminar flow in a wind tunnel. Seventeen different sets of parameters related to dimple diameter (mm), dimple orientation (angle) and air stream velocity (m/s) were studied. The Box-Behnken of Response Surface Methodology (RSM) was used as design of experiments (DoE) tool to evaluate these parameters on cooling time. This work deals with the analysis of variance (ANOVA) in order to establish the significant effect of input parameters. The result reveals that an increase in dimple diameter and air stream velocity increase heat dissipation. The shortest cooling time of 7 minutes can be achieved when the dimple diameter is 12 mm; the dimple orientation is 60° and air flow velocity at 18 m/s. The mathematical model has been rendered where the model has been experimentally validated with the average error of 6%.

scholarly journals Avian thermoregulation in the heat: is evaporative cooling more economical in nocturnal birds?

2018 ◽  
Author(s):  
Ryan S. O’Connor ◽  
Ben Smit ◽  
William A. Talbot ◽  
Alexander R. Gerson ◽  
R. Mark Brigham ◽  
...  
Keyword(s):  
Heat Dissipation ◽  
Heat Waves ◽  
Evaporative Cooling ◽  
Evaporative Heat Loss ◽  
Arid Environments ◽  
Evaporative Water ◽  
Air Temperatures ◽  
Nocturnal Species ◽  
Diurnal Species ◽  
Intense Heat

AbstractEvaporative 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 than those of diurnal species that permit them 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 Tabetween 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 to diurnal species of similar mass. In contrast, nocturnal activity was positively correlated with EHL/MHP, indicating a greater capacity for evaporative cooling in nocturnal birds. However, our analysis also revealed conspicuous differences among nocturnal taxa. Caprimulgids and Australian-owlet nightjars had shallower slopes and reduced EWL compared to similarly-sized diurnal species, whereas owls had EWL rates comparable to diurnal species. Consequently, our results did not unequivocally demonstrate more economical cooling among nocturnal birds. Owls predominately select refugia with cooler microclimates, but the more frequent and intense heat waves forecast for the 21stcentury may increase microclimate temperatures and the necessity for active heat dissipation, potentially increasing owls’ vulnerability to dehydration and hyperthermia.

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