Estimates Of Daily Energy Expenditure Research Articles

Seasonal sex–specific energy expenditure in breeding and non‐breeding Palestine sunbirds Nectarinia osea

The timing of the chick‐rearing phase is known to have a profound effect on the reproductive success of birds. However, little is known about the energetic costs faced by the parents during different periods of the breeding season. These costs may have vital consequences for both their survival and future reproduction. In most studies, daily energy expenditure (DEE) of breeding and non‐breeding birds has been compared, without controlling for the effect of season. In the present study, we examined the energy demands of breeding compared to non‐breeding Palestine sunbirds Nectarinia osea and whether there were sex‐specific differences in DEE within and between different seasons. We predicted that DEE would be elevated when birds rear chicks, especially at cooler ambient temperatures. Time‐energy budgets were constructed for pairs of sunbirds, rearing chicks, or not breeding, in spring and summer. There were significant seasonal differences in estimates of DEE in non‐breeders that were 21% higher in spring than in summer. We attributed these to increases in non‐flight metabolic rate rather than changes in time spent on different activities. Our estimates of DEE for the birds that were rearing chicks were higher than non‐breeding adults. In females the increase in DEE when breeding, compared to when not breeding, was similar in both spring and summer, while males increased their DEE much less when breeding in spring. The differences in estimated DEE, however, were not significant between male and female birds in any season. Between seasons, female breeders had 17.1% higher DEE in spring than in summer, while male breeders showed no difference in DEE when rearing chicks in different seasons. Accordingly, our initial prediction was supported, as DEE in chick‐rearing adults was higher than in non‐breeding adults. In addition, although temperatures are lower in spring, breeding in the spring is only more costly than breeding in summer for females. Apparently, males are more flexible in reallocating their time and energy spent on different activities.

Factorial estimation of daily energy expenditure using a simplified method was improved by adjustment for excess post-exercise oxygen consumption and thermic effect of food

This study validated a simplified factorial method for measuring energy expenditure (EE) against EE measured by doubly labelled water (DEE), and investigated whether adjustment for excess post-exercise oxygen consumption (EPOC) and thermic effect of food (TEF) as described by Institute of Medicine (2002) improved the factorial measure. Seventeen normal weight subjects (10 females, seven males) were recruited from among university staff and students. Factorial EE was measured using a 16-activity-category method, published energy costs of activities and measured basal metabolic rate, before (FEE) and after (FEE(adj)) adjustment for EPOC and TEF, and by DEE. FEE underestimated daily EE by 14.6% relative to DEE (P = 0.000), but this underestimate was improved to 5.1% (P = 0.071) when FEE was adjusted for EPOC and TEF. Individual differences between DEE and FEE(adj) ranged from -20.2 to 17.6%, with 88% of subjects showing differences of less than +/-12%.

Energetics in Homo erectus and other early hominins: The consequences of increased lower-limb length

Previous studies of daily energy expenditure (DEE) in hominin fossils have estimated locomotor costs using a formula that was based on six species, all 18 kg or less in mass, including no primates, and that has a number of other problems when applied in an ecological context. It is well established that the energetic cost of human walking is lower than that of representative mammals, particularly for individuals with long lower limbs. The current study reevaluates the daily energy expenditures of a variety of hominin species using more appropriate approaches to estimating locomotor costs. To estimate DEE for primates, I relied on published data on body mass, day range, and the percentage of time spent in various activities. Based on those data, I calculated a value for nonlocomotor DEE. I then used a variant of a method that I have suggested elsewhere to calculate the daily cost due to locomotion (DEEL) and summed the two to calculate total DEE. The more up-to-date methods for calculating the cost of travel result in lower estimates of this aspect of the energy budget than seen in previous studies. Values obtained here for DEE in various representatives of Australopithecus are lower than reported previously by around 200 kcal/day. Taking into account the greater economy of human walking, particularly the effect of the longer lower limbs found in many later Homo species, also results in lowered estimates of DEE. Elongation of the lower limbs in H. erectus reduced relative travel costs nearly 50% in comparison to A.L. 288-1 ( A. afarensis). The present method for calculating DEE indicates that female H. erectus DEE was 84% greater than that of female Australopithecus; this disparity is even larger than that suggested by previous workers.

Comparison of Predicted REE by the Actical® Activity Monitor with Indirect Calorimetry

The prevalence of obesity continues to increase throughout the world. While it is well known that a positive energy balance is the primary factor contributing to this epidemic, there is a great need to improve our understanding of how relatively small changes in physical activity contribute to energy balance. Actical® Physical Activity Monitors (ActMon) are designed to measure activity and provide estimates of daily energy expenditure using an algorithm that calculates resting energy expenditure (REE). Yet, it is not known exactly how well REE predicted from this algorithm compares to more precise estimates of REE. Therefore, REE predicted by the ActMon (ActMon REE) was compared to REE estimated with an indirect calorimeter (IC REE). Using a sample of 50 men and women between 18 and 43 years of age, we measured REE with the two methods described and percent body fat (%BF) using a bioelectrical impedance scale. The ActMon REE was 28.5 kcal greater than the IC REE. When the sample was split by %BF (<25 and ≥ 25.0), it was found that the ActMon over predicted REE more for those persons with > 25.0 %BF than for those with <25 %BF. The data were also split by gender since there was a significant gender by %BF interaction and the greater the %BF, the more the ActMon over predicted REE, for men only. Thus, the ActMon may be useful for large cohort studies, but some caution must be exercised when using the device in persons with either high or low %BF.

The Effects of Conjugated Linoleic Acid Supplementation during Resistance Training

We determined the effects of conjugated linoleic acid (CLA) supplementation during resistance training. Seventy-six subjects were randomized to receive CLA (5 g.d(-1)) or placebo (PLA) for 7 wk while resistance training 3 d.wk(-1). Seventeen subjects crossed over to the opposite group for an additional 7 wk. Measurements at baseline, 7 wk, and 14 wk (for subjects in the crossover study) included body composition, muscle thickness of the elbow flexors and knee extensors, resting metabolic rate (RMR), bench and leg press strength, knee extension torque, and urinary markers of myofibrillar degradation (3-methylhistidine (3MH) and bone resorption (cross-linked N-telopeptides (Ntx)). After 7 wk the CLA group had greater increases in lean tissue mass (LTM) (+1.4 vs +0.2 kg; P < 0.05), greater losses of fat mass (-0.8 vs +0.4 kg; P < 0.05), and a smaller increase in 3MH (-0.1 vs + 1.3 micromol.kg LTM.d(-1); P < 0.05) compared with PLA. Changes between groups were similar for all other measurements, except for a greater increase in bench press strength for males on CLA (P < 0.05). In the crossover study subjects had minimal changes in body composition, but smaller increases in 3MH (-1.2 vs +2.2 micromol.kg LTM.d(-1); P < 0.01) and NTx (-4.8 vs +7.3 nmol.kg(-1) LTM.d(-1); P < 0.01) while on CLA versus PLA. Supplementation with CLA during resistance training results in relatively small changes in body composition accompanied by a lessening of the catabolic effect of training on muscle protein.

A NEW MODEL TO ESTIMATE DAILY ENERGY EXPENDITURE FOR WINTERING WATERFOWL

Current models to estimate daily energy expenditure (DEE) for free-living birds are limited to either those that use fixed thermoregulatory costs or those that more accurately estimate thermoregulatory costs, but require extensive and often logistically difficult measurements. Here, we propose a model based on basal metabolic rate (BMR), activity budgets, and site-specific energetic costs of thermoregulation that requires only simple measures of ambient temperature and wind speed to provide estimates of DEE. We use the model to calculate the DEE of Buffleheads ( Bucephala albeola) wintering at six habitats that afford differing degrees of protection from exposure within Narragansett Bay, Rhode Island. Bufflehead activity budget data collected during the winters of 2001-2002 and 2002-2003, along with average temperatures and wind speeds at the sites, were used to calculate DEE that ranged from 46.9 to 52.4 kJ/hr and increased with increasing wind speed. The energetic cost of thermoregulation composed as much as 28% of total DEE and increased with wind speed. Our DEE values were 13.4% higher, and thermoregulatory costs were up to 2 3 higher than those calculated using an existing model that incorporates fixed thermoregulatory costs. We also saw an increase in feeding activity with increasing wind speed; sensitivity analysis of the effects of wind speed and feeding activity showed that a 1 m/sec increase in wind speed at our sites increased DEE by 2.5%, whereas a corresponding increase in feeding activity increased DEE by 4.5%. This suggests that in temperate winter habitats, increased feeding activity may have a greater impact on Bufflehead DEE than wind exposure. Site-specific model estimates of DEE could also provide additional insight into the relative contribution of environmental conditions and changes in waterfowl behavior to DEE. Received 27 May 2004, accepted 12 January 2005.

DAQIHF: methodology and validation of a daily activity questionnaire in heart failure.

To assess the validity, reliability, and sensitivity of a new self-administered physical activity questionnaire estimating daily energy expenditure (DEE) in patients with congestive heart failure (CHF). There is a need to develop a low cost, practical, and accurate tool increasing the knowledge of the type and dose of physical activity in patients with CHF for clinical and epidemiological aims. One hundred five participants with stable CHF performed an incremental symptom-limited VO2(peak) test and completed the questionnaire. For DEE calculation, time spent in each activity was multiplied by its energy cost corrected for weight, age, sex, autonomy, and the total was calculated over 24 h. Reproducibility and sensitivity of the questionnaire as well as interrater reliability were tested. Concurrent validity was assessed against VO2(peak), anthropometric characteristics and data from the literature. Test-retest correlation coefficients used to measure reproducibility ranged from 0.82 for activities ranging from 3 to 5 METs to 0.98 for DEE and a paired Student's t-test didn't reach statistical significance for any activity score studied. Interrater reliability was high with an error in DEE estimation of 1.37% (t value = -1.064; P = NS). Sensitivity (changes in VO2(peak) concurrent to changes in DEE) was high (r = 0.88, P < 0.0001). DEE was in line with the literature in patients with CHF and relationships between DEE and VO2(peak) (r = 0.71, P < 0.0001), and DEE and anthropometric characteristics (<0.0001) were significant. Activity level above 3 METs was the best intensity criteria related to VO2(peak) (r = 0.62, P < 0.0001) and DEE (r = 0.80, P < 0.0001). The questionnaire seems reliable, sensitive and valid for the estimation of DEE. VO2(peak) appears related to global DEE and more particularly to activities above 3 METs in patients with CHF.

A questionnaire-based assessment of daily physical activity in heart failure.

Type and dose of daily energy expenditure (DEE) play a major role in modulations of health status and an increased knowledge of these dimensions of physical activity in congestive heart failure (CHF) patients would be valuable for clinical and epidemiological aims. We propose a new self-administered DEE questionnaire adapted to CHF patients and tested its validity. One hundred and five stable CHF participants, NYHA class I-IV, LVEF=33.2+/-6.1% performed an incremental symptom-limited Vo(2) (peak) test and filled in the questionnaire for DEE calculation. Reproducibility (n=24), sensitivity (n=21) of the questionnaire and inter-observer variability (n=105) were tested. Intensity levels were identified from DEE and their relationships to Vo(2)(peak), ventilatory and anthropometric characteristics were assessed by simple and multiple regression models. Reproducibility and sensitivity were high (r=0.98 and 0.88, respectively, P<0.0001) and inter-observer error reached 1.37%. DEE was highly correlated to physical activity energy expenditure (r=0.96, P<0.0001). Relationships between DEE, Vo(2)(peak), V(E)/Vo(2) and anthropometric characteristics were significant. An activity level above 3 MET was the best intensity criteria related to Vo(2)(peak) (r=0.62, P<0.0001) and DEE (r=0.80, P<0.0001). The questionnaire seems reproducible, sensible and valid for DEE estimation. Vo(2)(peak) appears related to DEE and especially to activities above 3 MET in CHF.

A questionnaire-based assessment of daily physical activity in heart failure

Type and dose of daily energy expenditure (DEE) play a major role in modulations of health status and an increased knowledge of these dimensions of physical activity in congestive heart failure (CHF) patients would be valuable for clinical and epidemiological aims. We propose a new self-administered DEE questionnaire adapted to CHF patients and tested its validity. One hundred and five stable CHF participants, NYHA class I–IV, LVEF=33.2±6.1% performed an incremental symptom-limited Vo2 (peak) test and filled in the questionnaire for DEE calculation. Reproducibility (n=24), sensitivity (n=21) of the questionnaire and inter-observer variability (n=105) were tested. Intensity levels were identified from DEE and their relationships to Vo2(peak), ventilatory and anthropometric characteristics were assessed by simple and multiple regression models. Reproducibility and sensitivity were high (r=0.98 and 0.88, respectively, P<0.0001) and inter-observer error reached 1.37%. DEE was highly correlated to physical activity energy expenditure (r=0.96, P<0.0001). Relationships between DEE, Vo2(peak), VE/Vo2 and anthropometric characteristics were significant. An activity level above 3 MET was the best intensity criteria related to Vo2(peak) (r=0.62, P<0.0001) and DEE (r=0.80, P<0.0001). The questionnaire seems reproducible, sensible and valid for DEE estimation. Vo2(peak) appears related to DEE and especially to activities above 3 MET in CHF.

Estimated daily energy expenditure and blood lipids in adolescents: the Québec family study

Purpose To examine the association between estimated daily energy expenditure and blood lipids in a sample of adolescents. Methods The sample consisted of 415 males and 356 females aged 10–19 years, mainly French Canadian, recruited from the greater Quebec City area through the media as part of Phase I of the Quebec Family Study. Estimates of daily energy expenditure (DEE) were obtained with a 3-day physical activity record. Blood lipids were measured by standard procedures. The sample was stratified into three activity groups (least active, less than 25th percentile of DEE; moderately active, 25–74th percentile of DEE; and most active, 75th percentile or greater of DEE), and also by clinical cutpoints for blood lipids. Analysis of covariance, controlling for age and fatness, was conducted to compare blood lipids within gender across activity groups. Logistic regression analysis, controlling for age and fatness, was used to estimate the relative risk of being classified with an undesirable level of a blood lipid parameter on the basis of the DEE. Results Total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels were not significantly different across activity groups in males or females. High-density lipoprotein cholesterol (HDL-C) was significantly different across activity groups in males ( p < .05) and females ( p < .05), but the pattern of variation was different between genders. In males, the TC/HDL-C and LDL-C/HDL-C ratios decreased between the moderately active and most active groups ( p < .05). Significant differences remained when subcutaneous fatness was considered as a covariate. The results from logistic regression analysis indicated that the odds ratios for low HDL-C levels was significant only in low DEE girls (odds ratio 2.83) compared with high DEE girls. Conclusions The results suggest that increased energy expenditure and physical activity are associated with higher levels of HDL-C in adolescents of both sexes.

Seasonal changes in energy and water use by verdins, Auriparus flaviceps.

We used the doubly labeled water (DLW) method to measure field metabolic rate (FMR) and water turnover during winter and summer in a very small (6.5 g) insectivorous desert passerine bird, the verdin (Auriparus flaviceps). Concurrently, we monitored weather conditions and used time-activity budget data of free-living birds and laboratory data on resting metabolic rate to construct time-activity laboratory (TAL) estimates of daily energy expenditure (DEE ) and to partition the verdins' energy budget into thermoregulatory, activity and basal components. The FMR of adult verdins was 33.6+/-0.9 kJ day(-)(1) (mean +/- s.e.m.; N=14) in winter and 22.8+/-0.45 kJ day(-)(1) (N=7) in summer. FMR correlated negatively with the mean standard operative environmental temperature (T(es)) prevailing during the measurement period. TAL analysis produced DEE estimates that corresponded on average to within -0.9+/-2.4 % of our DLW-measured FMR values (range of individual values -18.3 % to +14.3 %). Metabolic expeditures for cold defense were 19.5+/-2.1 % of DEE in winter (computed assuming substitution of exercise thermogenesis for thermoregulatory costs in active birds). In the summer, thermoregulatory costs amounted to 9.0+/-0.4 % of DEE for keeping warm and 1.0+/-0.1 % of DEE for keeping cool in the heat. Activity costs were 21.0+/-0.5 % of DEE in winter and 17.5+/-0.1 % of DEE in summer. The water efflux of nonbreeding adult verdins was 3.9+/-0.2 ml day(-)(1) (624+/-22 ml kg(-)(1 )day(-)(1)) in summer (N=5) and 3. 4+/-0.2 ml day(-)(1) (498+/-26 ml kg(-)(1 )day(-)(1)) in winter (N=14). The water economy index (WEI; water efflux per unit FMR) of verdins was higher in summer (0.17+/-0.01 ml kJ(-)(1)) than in winter (0.10+/-0.01 ml kJ(-)(1)) and correlated negatively with mean T(es).

Wintering Tufted Ducks Aythya fuligula Diving for Zebra Mussels Dreissena polymorpha Balance Feeding Costs within Narrow Margins of Their Energy Budget

Diving ducks face the strongly cooling properties of aquatic environments. In experiments with Tufted Ducks Aythya fuligula feeding on zebra mussels Dreissena polymorpha in outdoor cages, we measured changes in food consumption and diving behaviour in relation to water temperature (3-22 degrees C). Water efflux and daily energy expenditure (DEE) were measured using doubly-labelled water. Tufted Ducks swallow mussels whole and crush the shells in the gizzard. Due to the low flesh content of mussels, daily mussel consumption was extremely high in winter (up to 3 times the duck body mass of 600 g). Water efflux was 6.5 to 13 limes higher than allometrically predicted, with a maximum of 1.1 1 d(-1). Because of high water turnover rates, DEE estimates from doubly-labelled water measurements were variable, but on average agreed with DEE estimates obtained from food consumption and time-energy budgets (ca. 5% higher values). DEE increased with lower temperatures from 2.5 (summer, 20 degrees C) to more than 4 times the basal metabolic rate (winter, 3 degrees C). Costs of thermoregulation and heating up ingested mussels (as estimated from the theoretical caloric heat) primarily explained the high DEE in winter. At lower temperatures, dive duration was shorter and less time was spent selecting small mussels at the bottom, while more larger mussels were brought up and were ingested at the water surface. Thereby, the energy costs of crushing shells probably increased in favour of reducing diving costs. The narrow margins of the energy budget, wherein feeding costs must be balanced, imply that food availability and water temperature are important attributes to winter distributions of diving ducks.

CONTRIBUTIONS OF BODY COMPOSITION, ETHNICITY, AGE, AND PHYSICAL ACTIVITY TO TOTAL BODY BONE MINERAL DENSITY 964

The purpose of this cross-sectional study was to determine the relative contributions of body composition, ethnicity, age, and physical activity to total body bone mineral density (BMD) in Indian/Pakistani vs Caucasian 20 to 40 year old premenopausal women. We examined factors (height, weight, lean weight, energy expenditure, age) related to total body BMD in two distinct ethnic groups of healthy women (Indians/Pakistanis, n=47; Caucasians, n=47). Total body BMD and body composition were assessed via dual-energy x-ray absorptiometry (QDR-2000+. Hologic, Inc.). Daily energy expenditure estimates were obtained via the Five-City Project questionnaire. Mean height (cm), weight (kg), and lean weight (kg), respectively, were significantly(p<0.0001, p=0.0018, p=0.0001) lower in Indian/Pakistani (158.5, 56.8, 33.7) vs Caucasian (165.6, 62.3, 41.5) women. Mean energy expenditure/day and energy expenditure/kg/day, respectively, were also significantly (p<0.0001) lower in Indians/Pakistanis (1921, 33.8) vs Caucasians (2257, 36.3). Indian/Pakistani women had significantly(<0.0001) lower mean (± SD) total body BMD (1.008±0.078) compared to Caucasians (1.074±0.066), using one-tailedt-tests. Stepwise regression analysis indicated that the best model to explain the overall variance (35.1%, p<0.0001) in total body BMD included ethnicity (Indian/Pakistani vs Caucasian), age, and total body weight, each contributing 6.5%, 2.3%, and 12.8%, respectively. The model including bone-free lean weight (rather than total weight) had almost as high R2 (32.5%), but ethnicity was too highly correlated (r=0.665) with lean weight to be significant. Likewise, the contribution of energy expenditure(10.6%) to the overall model (R2=32.9%) was likely attenuated by its correlation with ethnicity (r=0.481). Although body weight was the most important predictor of BMD, it was the lean portion that exerted the greatest effect. The greater lean mass of the Caucasians compared with the Indians/Pakistanis may have been due to their higher levels of energy expenditure; alternatively, the dissimilarities in lean mass may be due to inherent ethnic differences in body composition, possibly placing them at greater osteoporotic risk.

Caltrac versus calorimeter determination of 24-h energy expenditure in female children and adolescents

The purpose of this study was to determine the validity of the Caltrac accelerometer for estimating 24-h energy expenditure (EE) in children and adolescents. EE for 40 girls (13.0 +/- 1.8 yr) was assessed for 24 h via indirect calorimetry in whole-room calorimeters. EE and activity level were estimated concurrently by two Caltrac accelerometers placed on the subjects at each hip. Significant correlations (P < 0.001) resulted between Caltrac estimates and calorimeter values for 24-h total EE (TEE, r = 0.80), sedentary daily EE (SDEE, r = 0.84), and waking EE (WEE, r = 0.85). Nonetheless, the Caltrac significantly (P < 0.001) underestimated EE in all experimental conditions (TEE: -13.3 +/- 8.6%; SDEE: -6.8 +/- 7.3%; WEE: -30.4 +/- 8.5%). A significant multiple correlation between calorimeter values and a combination of Caltrac activity counts and body weight (R = 0.86, P < 0.001) suggested these variables could be useful for daily EE estimation. Additional analyses indicated that as EE increased, the absolute difference between Caltrac and calorimeter values also increased. The significant correlations between Caltrac and calorimeter values suggest the Caltrac may be useful for assessing daily caloric expenditure for groups of children.

Measurements of energy expenditure using isotope-labelled water (2H2(18)O) during an Arctic expedition.

Estimates of energy expenditure using both isotope-labelled (2H2(18)O) water and dietary intake/body composition changes were made during an attempt by two men (MS and RF) to walk to the North Pole. The isotope-labelled water technique gave mean estimates of daily energy expenditure for the 48-day expedition of 28.05 MJ (MS) and 32.38 MJ (RF), which compared with estimates of 25.66 MJ (MS) and 24.86 MJ (RF) from the intake/body composition measurements. Fluid retention and peripheral oedema probably caused a considerable underestimate of the losses in body energy stores when applying the energy balance method, whereas in the isotope method, uncertainty in the measurements of isotopic background led to minimum errors of -4.9% to +4.0% of the means for MS and -12.7% to +8.2% for RF (95% confidence limits).

Estimation of Daily Energy Expenditure from Heart Rate and Doubly Labeled Water in Exercising Geese

We investigated whether daily O₂ consumption (V̇o2) could be predicted from heart rate (fH) in five exercising barnacle geese (Branta leucopsis) and compared the accuracy of this method with that of the doubly labeled water (DLW) method. The regressions of V̇o2 on fH, based on incremental speed tests, differed among individual birds. The O₂ pulse (i. e., V̇o2/fH) progressively increased with exercise level from 0.22 mL O₂ heartbeat⁻¹ during resting to an estimated 0.47 mL O₂ heartbeat⁻¹ during flight. Daily V̇o2, was generally underestimated (-3.9%) by (individual) resting O₂, pulses but overestimated (+8.4%) by linear regressions of V̇o2 on fH. However, it was wellpredicted (+0.8%) by the O₂ pulses appropriate for each exercise level When using relationships derived from the group of birds, the estimations were generally improved (-3.3% for resting O₂, pulse, -0.03% for appropriate O₂ pulse) but poorer (+13.6%) for the group linear regression. Some of these predictions were better than the estimation of daily CO₂ production (V̇o2) by the two-compartment model of the DLW method (average algebraic error of +0.9%). We conclude that fH can be used to estimate daily energy expenditure in birds accuratelyprovided that (1) its application is limited to the range of exercise levels in which fH has been calibrated against V̇o2 and (2a) V̇o2-fH relationships are determined for each individual bird or (2b) the fH measurements of several free-ranging birds are averaged. Heart rate can also be used to indicate within-day variation in energy expenditure.

Energetic limitation of avian parental effort: Field experiments in the kestrel (Falco tinnunculus)

AbstractWe studied the limiting factors for brood size in the kestrel, Falco tinnunculus, by measuring parental effort in natural broods of different size and parental response to manipulation of food satiation of the brood. Parental effort was quantified as total daily time spent in flight, and total daily energy expenditure, from all‐day observations.During nestling care males with different natural brood sizes (4 to 7 chicks), spent an average of 4.75 h · d−1 in flight independent of brood size, and expended an average total daily energy of 382 kJ · d−1. Due to a higher flight‐hunting yield (mammal‐prey caught per hour hunting), males with larger natural broods were able to provision their broods with the same amount of food (mainly Microtus arvalis) per chick (62.6 g · d−1), with the same effort as males with smaller broods. This provisioning rate was close to the mean feeding rate of hand‐raised chicks in the laboratory, that were fed ad libitum, (66.8 g · d−1 · chick−1).Our food deprivation experiments revealed that male kestrels strongly respond to food shortage in the nest. In the older nestling phase males on average increased their daily rate of food delivery to the nest as a response to experimental food deprivation by almost three times to 646.4 g · d−1, by increasing their flight activity level from 4.46 to 8.41 h · d−1. This increased energy expenditure was sustained, for as long as eleven days, by increasing the metabolizable energy intake up to what is presumed to be the maximum rate. Even under considerable experimental food stress (chicks not being satiated due to continuous removal of delivered food by the observers) about half of the available daylight time remained unused for foraging.We conclude 1) that the mean daily energy expenditure of males during nestling care — to which clutch size is apparently initially adjusted — is well below the maximum they are able to sustain and 2) that the energy expenditure they can sustain under extremely high nestling demand is not set by the available time for foraging or the available energy in the environment. Thus the birds normally operate well below their presumed maximum, and only during food shortage, e.g., as caused by our experiments, do they increase activity up to this maximum. Therefore we conclude that the kestrels have costs other than energy expenditure, such as parental survival, that are involved in the increased “cost” of parental effort.We discuss possible generalisations about existing energetic limitations during parental care in altricial birds. From published estimates of daily energy expenditure during parental care (DEEpar) in 30 different bird species we derived the equation: DEEpar = 14.26 kg0.65 Watt. This relationship differs significantly in slope (T = 2.49; p &gt; 0.02) from the allometric equation for the maximum rate of energy assimilation (DMEmax) as provided by Kirkwood (1983): DMEmax = 19.82 kg0.72 Watt. In smaller species (ca. 25 g) DEEpar about equals DMEmax, while in the larger species (ca. 10 kg) DEEpar represents only about 60% of the predicted DMEmax. This suggests that limitations in parental effort are more frequently set by the maximum sustainable energy intake in the smaller species than in larger species. Our allometric equations for DEEpar suggests that the relation between BMR, estimated using the equations of Aschoff and Pohl (1970), and the observed parental energy expenditure, is such that on average bird parents work at a daily level somewhere between 3 and 4 times BMR.

Estimates of Daily Energy Expenditure in Birds: The Time-Energy Budget as an Integrator of Laboratory and Field Studies

SYNOPSIS. Measures of energy expenditure by free-living birds can provide quantitative testsof a number of ecological theories, regarding such diverse phenomena as foraging strategies, resource competition, or parental investment. Our confidence in these tests rests heavily on the confidence we have in the estimated rates of energy expenditure. The most common approach to obtaining such estimates is the construction of time-energy budgets, in which the durations of ananimal's daily activities are multiplied by the respective energy costs of the activities, and these costs are summed. Our knowledge of the energy costs of activities, particularly locomotion, has greatly advanced in recent years, as has the ability to adequately assess thermoregulatory costs. Comparisons between timeenergy budgets and direct measures of energy expenditure obtained using doubly labeled water indicate that time-energy budgets can yield accurate estimates of energy expenditure. However, this is likely to be achieved only under fairly rigorous conditions in which resting costs, activity costs, and thermoregulatory costs are all well described.Evidence is accumulating to suggest that, under some conditions, energy expenditure by birds reaches a maximum sustainable level, at which point it is limited by the physiological capacitiesto ingest and assimilate energy. Under these conditions, behavioral responses to changing physical environments and resource availability may be critical to the maintenance of energy balance.

Energetics of the annual cycle of Dippers Cinclus cinclus

Time‐activity budgets and energy expenditure of Dippers Cinclus cinclus were studied in all months of the year and for every stage of the annual cycle. The commonest daytime activity was feeding (54%), then resting (43%) and flying (4%). On a 24‐hr day basis the most marked changes in activity followed from changing daylengths. DEE (Daily Energy Expenditure), derived from time‐activity budgets through the year and laboratory estimates of metabolism, averaged 201 kj d ‐1 in females and 228 kj d ‐1 in the larger males. Over a more restricted range of circumstances, direct estimates of DEE obtained from 77 Dippers using the doubly labelled water technique averaged 205 ± 43 kj d‐1 and 251 ± 55 kj d‐1 in females and males, respectively. Overall, the correspondence between these largely independent estimates of energy expenditure was reasonably close. DEE was highest during breeding (laying‐females; rearing‐males) and in late winter for both sexes. The lowest energy expenditures occurred during moult, amongst juveniles and in early winter. Incubating females and mate‐guarding males also had low energy costs. Across all stages of the annual cycle body size, activity patterns, ambient temperature and river flow had significant effects on energy expenditure. The rate at which food was gathered to meet these changing energy demands varied widely. While some of this variation was imposed by a seasonal environment, it was also likely to reflect adaptive shifts in rates of food gathering, in some cases consequent upon the changing fitness benefits of various non‐feeding activities.

Daily Energy expenditure by Adult Leach's Storm-Petrels during the Nesting Cycle

We measured metabolic rates of adult Leach's storm-petrels on Kent Island, New Brunswick, in order to determine the energetic costs of reproductive activities in a small, pelagic seabird. Oxygen consumption of captive birds was determined volumetrically, and daily energy expenditure of free-living individuals was estimated by the doubly labeled water technique (DLW). Errors inherent in DLW gave rise to expected standard deviations in estimates of CO₂ production on the order of 20%–30% of the mean, which were similar in magnitude to the variation observed among individual measurements. Furthermore, when final concentrations of 18O in body water were low, an apparent bias in the measurement of background 18O consistently inflated estimates of CO₂ production. Minimum rate of oxygen consumption occurred at 36 C and averaged 90 cm³ h⁻¹ or 1.92 cm³ g⁻¹ h⁻¹. Rate of oxygen consumption increased gradually with decreasing temperature and more rapidly below 16 C, at which point thermal conductance plus evaporative heat loss was 2.6–2.9 J g⁻¹ C⁻¹ h⁻¹. CO₂ production of incubating adults averaged 80 cm³ h⁻¹. Analysis of individuals collected at the beginning and end of the incubation spell indicated that about twothirds of the energy for incubation was supplied by fat deposits and the rest by stomach oils and that the ratio of fat to water loss during incubation was about 1.55 by mass. Carbon dioxide production of adults away from the nest during the first half of the nestling period averaged 191 cm³ h⁻¹. Water turnover rates were 0.136 day⁻¹ in incubating adults and 1.01 day⁻¹ in adults away from the nest. Estimates of daily energy expenditure (DEE) are consistent with Leach's storm-petrels' spending considerable time resting on the water surface while at sea. Ratios of energy expenditure to water turnover suggest that adults assimilate a less energy-dense diet than that which they feed their chicks.