Physiological ecologist, science communicator, hummingbirds. Currently a Rose Postdoctoral Fellow at the Cornell Lab of Ornithology. Address: Ithaca, New York, United States
Synopsis Torpor is an incredibly efficient energy-saving strategy that many endothermic birds and... more Synopsis Torpor is an incredibly efficient energy-saving strategy that many endothermic birds and mammals use to save energy by lowering their metabolic rates, heart rates, and typically body temperatures. Over the last few decades, the study of daily torpor—in which torpor is used for <24 h per bout—has advanced rapidly. The papers in this issue cover the ecological and evolutionary drivers of torpor, as well as some of the mechanisms governing torpor use. We identified broad focus areas that need special attention: clearly defining the various parameters that indicate torpor use and identifying the genetic and neurological mechanisms regulating torpor. Recent studies on daily torpor and heterothermy, including the ones in this issue, have furthered the field immensely. We look forward to a period of immense growth in this field.
Females and males can exhibit striking differences in body size, relative trait size, physiology,... more Females and males can exhibit striking differences in body size, relative trait size, physiology, and behavior. As a consequence, the sexes can have very different rates of whole-body energy use, or converge on similar rates through different physiological mechanisms. Yet many studies that measure the relationship between metabolic rate and body size only pay attention to a single sex (more often males), or do not distinguish between sexes. We present four reasons why explicit attention to energy-use between the sexes can yield insight into the physiological mechanisms that shape broader patterns of metabolic scaling in nature. First, the sexes often differ considerably in their relative investment in reproduction, which shapes much of life-history and rates of energy use. Second, males and females share a majority of their genome but may experience different selective pressures. Sex-specific energy profiles can reveal how the energetic needs of individuals are met despite the chall...
Contains descriptions for all dataset files accompanying this paper (each column and its possible... more Contains descriptions for all dataset files accompanying this paper (each column and its possible values are described)
Respirometry measurements of oxygen consumption for Costa's hummingbirds in a temperature-con... more Respirometry measurements of oxygen consumption for Costa's hummingbirds in a temperature-controlled chamber. Used to model the thermoneutral zone for broad-billed hummingbirds. Data collected in 1986 by DR Powers
1. Managing energy stores in response to variable resource availability is a key component to ind... more 1. Managing energy stores in response to variable resource availability is a key component to individual fitness, yet because directly measuring energy budgets is difficult, daily energy management is rarely measured. 2. Hummingbirds’ energy management is relatively simple to model compared to other endotherms because they have high mass-specific metabolic rates and store little fat. 3. We determined which aspects of the hummingbird daily energy budget (i.e. thermoregulation, daytime activity costs, nighttime costs) change at the individual level in response to environmental variation. 4. We found that daily energy expenditure varied three-fold in two populations of broad-billed hummingbirds (Cynanthus latirostris). 5. Our model indicated the energy budget was distributed in the following proportions: daytime activity, 59% (range 22-84%); thermoregulation, 23% (11 – 32%), basal metabolism, 7% (3 – 16%), and nighttime energy 17% (6 – 37%). Activity costs were higher at the hotter, homogeneous site and during the early-wet season at both sites. 6. Increased daily energy expenditure was related to decreased nectar availability, and not significantly related to temperature or bird mass. With climate change, the indirect energetic costs of shifting resources could have greater impacts on endotherm energy budgets than direct costs such as thermoregulation. Increased foraging and activity costs could decrease the energy available to birds for somatic repair and reproduction, potentially causing differential fitness across seasons and sites
Hummingbirds' daily energy expenditure scales with an unusually high slope with mass. The all... more Hummingbirds' daily energy expenditure scales with an unusually high slope with mass. The allometric slopes of their daily activities, unusual relative to other birds - from their ability for minimal energy expenditure in torpor, to their extremely high-powered hovering flight- seem to explain their high daily energy expenditure slope.
Code associated with the Functional Ecology article titled "Hummingbirds budget energy flexi... more Code associated with the Functional Ecology article titled "Hummingbirds budget energy flexibly in response to changing resources"
ABSTRACTTorpor is an important energy saving strategy in small endotherms, but it has been insuff... more ABSTRACTTorpor is an important energy saving strategy in small endotherms, but it has been insufficiently studied in natural field conditions. Building on what we know from laboratory studies, we compared torpor use across hummingbird species and different natural temperature regimes to explore predominant hypotheses about torpor use and evaluate the possible effects of environmental variation on energy management.We found that the probability of an individual entering torpor was correlated with mass and unrelated to nighttime temperature, and that hummingbirds at both warm tropical and cooler temperate sites used torpor.Energy savings in torpor were maximized as ambient temperatures approached a species’ minimum body temperature consistent with laboratory studies; energy savings ranged between 65-92% of energy per hour in torpor compared to normothermy.However, variation in total nighttime energy expenditure was more significantly influenced by torpor bout duration than by the vari...
Many endotherms use torpor, saving energy by a controlled reduction of their body temperature and... more Many endotherms use torpor, saving energy by a controlled reduction of their body temperature and metabolic rate. Some species (e.g., arctic ground squirrels, hummingbirds) enter deep torpor, dropping their body temperatures by 23-37°C, while others can only enter shallow torpor (e.g., pigeons, 3-10°C reductions). However, deep torpor in mammals can increase predation risk (unless animals are in burrows or caves), inhibit immune function, and result in sleep deprivation, so even for species that can enter deep torpor, facultative shallow torpor might help balance energy savings with these potential costs. Deep torpor occurs in three avian orders, but the trade-offs of deep torpor in birds are unknown. Although the literature hints that some bird species (mousebirds and perhaps hummingbirds) can use both shallow and deep torpor, little empirical evidence of such an avian heterothermy spectrum within species exists. We infrared imaged three hummingbird species that are known to use de...
Synopsis Torpor is an incredibly efficient energy-saving strategy that many endothermic birds and... more Synopsis Torpor is an incredibly efficient energy-saving strategy that many endothermic birds and mammals use to save energy by lowering their metabolic rates, heart rates, and typically body temperatures. Over the last few decades, the study of daily torpor—in which torpor is used for <24 h per bout—has advanced rapidly. The papers in this issue cover the ecological and evolutionary drivers of torpor, as well as some of the mechanisms governing torpor use. We identified broad focus areas that need special attention: clearly defining the various parameters that indicate torpor use and identifying the genetic and neurological mechanisms regulating torpor. Recent studies on daily torpor and heterothermy, including the ones in this issue, have furthered the field immensely. We look forward to a period of immense growth in this field.
Females and males can exhibit striking differences in body size, relative trait size, physiology,... more Females and males can exhibit striking differences in body size, relative trait size, physiology, and behavior. As a consequence, the sexes can have very different rates of whole-body energy use, or converge on similar rates through different physiological mechanisms. Yet many studies that measure the relationship between metabolic rate and body size only pay attention to a single sex (more often males), or do not distinguish between sexes. We present four reasons why explicit attention to energy-use between the sexes can yield insight into the physiological mechanisms that shape broader patterns of metabolic scaling in nature. First, the sexes often differ considerably in their relative investment in reproduction, which shapes much of life-history and rates of energy use. Second, males and females share a majority of their genome but may experience different selective pressures. Sex-specific energy profiles can reveal how the energetic needs of individuals are met despite the chall...
Contains descriptions for all dataset files accompanying this paper (each column and its possible... more Contains descriptions for all dataset files accompanying this paper (each column and its possible values are described)
Respirometry measurements of oxygen consumption for Costa's hummingbirds in a temperature-con... more Respirometry measurements of oxygen consumption for Costa's hummingbirds in a temperature-controlled chamber. Used to model the thermoneutral zone for broad-billed hummingbirds. Data collected in 1986 by DR Powers
1. Managing energy stores in response to variable resource availability is a key component to ind... more 1. Managing energy stores in response to variable resource availability is a key component to individual fitness, yet because directly measuring energy budgets is difficult, daily energy management is rarely measured. 2. Hummingbirds’ energy management is relatively simple to model compared to other endotherms because they have high mass-specific metabolic rates and store little fat. 3. We determined which aspects of the hummingbird daily energy budget (i.e. thermoregulation, daytime activity costs, nighttime costs) change at the individual level in response to environmental variation. 4. We found that daily energy expenditure varied three-fold in two populations of broad-billed hummingbirds (Cynanthus latirostris). 5. Our model indicated the energy budget was distributed in the following proportions: daytime activity, 59% (range 22-84%); thermoregulation, 23% (11 – 32%), basal metabolism, 7% (3 – 16%), and nighttime energy 17% (6 – 37%). Activity costs were higher at the hotter, homogeneous site and during the early-wet season at both sites. 6. Increased daily energy expenditure was related to decreased nectar availability, and not significantly related to temperature or bird mass. With climate change, the indirect energetic costs of shifting resources could have greater impacts on endotherm energy budgets than direct costs such as thermoregulation. Increased foraging and activity costs could decrease the energy available to birds for somatic repair and reproduction, potentially causing differential fitness across seasons and sites
Hummingbirds' daily energy expenditure scales with an unusually high slope with mass. The all... more Hummingbirds' daily energy expenditure scales with an unusually high slope with mass. The allometric slopes of their daily activities, unusual relative to other birds - from their ability for minimal energy expenditure in torpor, to their extremely high-powered hovering flight- seem to explain their high daily energy expenditure slope.
Code associated with the Functional Ecology article titled "Hummingbirds budget energy flexi... more Code associated with the Functional Ecology article titled "Hummingbirds budget energy flexibly in response to changing resources"
ABSTRACTTorpor is an important energy saving strategy in small endotherms, but it has been insuff... more ABSTRACTTorpor is an important energy saving strategy in small endotherms, but it has been insufficiently studied in natural field conditions. Building on what we know from laboratory studies, we compared torpor use across hummingbird species and different natural temperature regimes to explore predominant hypotheses about torpor use and evaluate the possible effects of environmental variation on energy management.We found that the probability of an individual entering torpor was correlated with mass and unrelated to nighttime temperature, and that hummingbirds at both warm tropical and cooler temperate sites used torpor.Energy savings in torpor were maximized as ambient temperatures approached a species’ minimum body temperature consistent with laboratory studies; energy savings ranged between 65-92% of energy per hour in torpor compared to normothermy.However, variation in total nighttime energy expenditure was more significantly influenced by torpor bout duration than by the vari...
Many endotherms use torpor, saving energy by a controlled reduction of their body temperature and... more Many endotherms use torpor, saving energy by a controlled reduction of their body temperature and metabolic rate. Some species (e.g., arctic ground squirrels, hummingbirds) enter deep torpor, dropping their body temperatures by 23-37°C, while others can only enter shallow torpor (e.g., pigeons, 3-10°C reductions). However, deep torpor in mammals can increase predation risk (unless animals are in burrows or caves), inhibit immune function, and result in sleep deprivation, so even for species that can enter deep torpor, facultative shallow torpor might help balance energy savings with these potential costs. Deep torpor occurs in three avian orders, but the trade-offs of deep torpor in birds are unknown. Although the literature hints that some bird species (mousebirds and perhaps hummingbirds) can use both shallow and deep torpor, little empirical evidence of such an avian heterothermy spectrum within species exists. We infrared imaged three hummingbird species that are known to use de...
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