Energy Assimilation Efficiency Research Articles

Energy Content, Moisture Content, and Energy Assimilation Efficiency by Birds and Mammals of Oil-Containing Seeds and Implications for Seed Treatment Risk Assessments for Birds and Mammals.

Energy content, moisture content, and energy assimilation efficiency are essential parameters in the food intake rate (FIR) and exposure calculations for bird and mammal risk assessments. The updated European Food Safety Authority guidance document on risk assessment for birds and mammals summarizes these parameters for different food items. For seed treatments, values for cereal seeds are proposed as surrogates for other crops. Oil-containing seeds are expected to have a higher energy content than cereal seeds. This would result in lower FIR and, thus, exposure from consuming such seeds. To be able to calculate reliable exposure values for risk-assessment purposes, we conducted a systematic literature review to collect information on these three parameters for oil-containing seeds (sunflower, oilseed rape, soybean, peanut, sesame, safflower, linseed [flax], white mustard, and castor bean). The search yielded 401 papers, of which 151 contained values for at least one of the parameters of the crops in focus. The overall average energy content value of oil-containing seeds was 24.25 kJ/g (n = 124, SD = 3.00), whereas that for moisture content was 6.57% (n = 296, SD = 1.15). Energy assimilation values were only available for peanut, oilseed rape, soy, linseed, and sunflower for a limited number of bird and mammal species. Mean energy assimilation efficiency for mammals was 82.69% (n = 4, SD = 1.55), whereas values for birds were 57.54% (n = 2, SD = 6.77) for Galliformes and 79.25% (n = 2, SD = 1.82) for Passeriformes. The values presented can be used to calculate appropriate FIR values for future bird and mammal risk assessments. Environ Toxicol Chem 2024;43:2080-2085. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

PGPR-based biofertilizer modulates strawberry photosynthetic apparatus tolerance responses by severe drought, soil salinization and short extreme heat event

Drought, soil salinization and the extreme heat events increments associate to climate change will notably impact sensitive crop species, such as strawberry. A greenhouse experiment was arranged to evaluate the potential of a PGPR-based biofertilizer, with multiple PGP properties, including ACC deaminase production highly related to the limitation of ethylene levels under abiotic stress, in modulation of photosynthetic apparatus tolerance responses by severe drought (complete water withholding), salinity in irrigation water (340 mM NaCl) and short extreme heat event (37/28 °C maximum and minimum temperature range). Our results show that all stress factors triggered acute injury effects on strawberry carboxylation capacity and photosystem II energy assimilation efficiency ability; whose intensity varied depending on factor nature. However, bacterial inoculation diminished ∼67 %, 20 % and 18 % the deleterious impact imposed by drought, heat and salinity stress on the net photosynthetic rate (AN). This effect was primarily mediated by counterbalancing the diffusion of CO2 in the stomata and biochemical limitations in response to heat and salinity stress, while the reduction of biochemical damage was more notable in response to drought. Complementarily, inoculation was able to highly buffer the photochemical limitations imposed by all abiotic stress factors tested. Despite these positive effects, the application of PGPR-based biofertilizer was unable to completely reverse the impact of stress factors on strawberry photosynthesis metabolism. However, the signal of these ameliorative effects was significant enough to consider the implementation of PGPR-based biofertilizer application as a complementary tool in the management of strawberry cultivation in increasingly stressful agronomic contexts.

Sex and State-Dependent Effects on Proactive Behaviors of Bent-Wing Bats Across Contexts

Synopsis Animals within a population may show distinct behavioral types that differ consistently among individuals over time and across contexts, collectively known as animal personality. Individual state variables arising from intrinsic features of organisms and their interactions with the environment may contribute to or aid in maintaining these interindividual behavioral differences. The present study examined the effects of body mass, body condition, flight morphology, and parasite load on the personality traits of bent-wing bats Miniopterus fuliginosus. We assessed the bats in three testing contexts—hole-board box (HB), tunnel-box (TB), and flight-tent (FT)—that mimicked their natural environmental settings and allowed for different locomotion modes. A principal component analysis loaded the three mutually positively correlated personality traits of the bats—boldness, activity, and exploration—in each context onto a single component of proactiveness. In accordance with the AIC criteria, sex, body mass, body condition index, and wingtip shape were selected as predictors for the proactiveness of the bats in the TB and FT tests. In the HB tests, the biomass and abundances of parasitic bat flies were additionally selected, but body condition was excluded. We found a negative effect of the body mass on the proactiveness of the female bats in both the HB and FT tests, and that on the proactiveness of the male bats in the HB tests but not so in the FT tests. The sexual differences and negative correlation between the body mass of the bats and their proactive responsiveness are consistent with the mechanism of state-dependent energy assimilation efficiency. Our results may also concur with the predicted feedback mechanism stemming from the characteristic conditions associated with the environment of the bats. This latter inference offers insights for exploring the patterns of personality traits along gradients or the seasonality of ecological conditions.

Optimization of integrated energy system considering transmission and distribution network interconnection and energy transmission dynamic characteristics

The traditional hierarchical scheduling and operational model of transmission and distribution networks has failed to fully utilize the adjustable resources of the entire grid, consequently limiting the integration of renewable energy. To fully excavate the potential of transmission and distribution (T&D) coordination in enhancing the level of renewable energy assimilation and operational efficiency, in this paper, transmission grid and distribution network in the framework of synergetic unit commitment (TDS-UC) considering the dynamic characteristics of the electricity-gas-heat integrated energy system is proposed. The framework developed in this paper allows for the integration of multiple energy sources, including electricity, gas, and heat, into the dispatch strategy of the TG. To improve scheduling flexibility, the dynamic characteristics of the natural gas and heating networks are also considered in the TDS-UC model. A coordinated interactive optimization model for T&D is formulated, taking into account the multi-energy coupling relationship of the IES. To solve the TDS-UC model, a decentralized analytical target cascading algorithm is used to obtain an independent TG optimization problem and multiple ADNs local optimization problems that can be solved in parallel. The proposed model is transformed into an easy-to-solve mixed-integer linear programming (MILP) problem using an improved one-dimensional approximation piecewise linearization method to deal with the non-convexity nonlinear natural gas Weymouth equation. Numerical experiments are conducted on both a T6D2 and a T118D10 test system to demonstrate the efficiency and practicality of the proposed methodology.© 2017 Elsevier Inc. All rights reserved.

Role of temperature on growth and metabolic rate in the tenebrionid beetles Alphitobius diaperinus and Tenebrio molitor

Insects are increasingly used as a dietary source for food and feed and it is therefore important to understand how rearing conditions affect growth and development of these agricultural animals. Temperature is arguably the most important factor affecting metabolism and growth rate in insects. Here, we investigated how rearing temperature affected growth rate, growth efficiency and macronutrient composition in two species of edible beetle larvae: Alphitobius diaperinus and Tenebrio molitor.Growth rates of both species were quantified at temperatures ranging from 15.2 to 38.0 °C after which we measured protein and lipid content of the different treatment groups. Metabolic rate was measured in a similar temperature range by measuring the rate of O2 consumption (V·O2) and CO2 production (V·CO2) using repeated measures closed respirometry. Using these measurements, we calculated the growth efficiency of mealworms by relating the energy assimilation rate to the metabolic rate. Maximum daily growth rates were 18.3% and 16.6% at 31 °C, for A. diaperinus and T. molitor respectively, and we found that A. diaperinus was better at maintaining growth at high temperatures while T. molitor had superior growth at lower temperatures. Both species had highest efficiencies of energy assimilation in the temperature range of 23.3–31.0 °C, with values close to 2 J assimilated/J metabolised in A. diaperinus and around 4 J assimilated/J metabolised in T. molitor. Compared to “conventional” terrestrial livestock, both species of insects were characterised by high growth rates and very high energy conversion efficiency at most experimental temperatures. For A. diaperinus, lipid content was approximately 30% of dry mass and protein content approximately 50% of dry mass across most temperatures. Temperature had a greater influence on the body composition of T. molitor. At 31.0 °C the lipid and protein content was measured to 47.4% and 37.9%, respectively but lipid contents decreased, and protein contents increased when temperatures were higher or lower than 31.0 °C.In summary, rearing temperature had large and independent effects on growth rate, energy assimilation efficiency and protein/lipid content. Accordingly, temperature is a critical parameter to control in commercial insect rearing regardless if the producer wants to optimise production speed, production efficiency or product quality.

Sexual Differences in Growth Rates of Juveniles from a Litter ofBothrops fonsecai: The Role of Feeding Conversion in a Female-Biased SSD Species

The mechanism behind the female-biased sexual size dimorphism in snakes (SSD) is usually linked to a delay in females' maturation and/or higher growth rates during their immature phase. Studies on growth rates of immature snakes have been focused on sex differences related to feeding rates instead of food conversion rates. We tested the hypothesis that growth rates of immature female lanceheads are higher than that of immature males and determined if this difference is related to differential food conversion rates between genders. During 18 months, we collected data on growth rates in juveniles from a litter of a species (Bothrops fonsecai) with a female-biased sexual size dimorphism under a controlled feeding regime. Our results showed that females, even receiving the same amount of food than males, presented higher growth rates in all parameters measured (snout-vent length, mass, stoutness, snout-vent length-specific growth rate and mass-specific growth rate). Our data support a mechanism of establishment of sexual size dimorphism in a female-biased species apart from feeding rates but linked to a different feeding conversion between sexes. Based on our results, we also suggest that these differences in feeding conversion must be linked to sexual differences in energy assimilation efficiency.

Comparative Bioenergetics of Diploid and Triploid Pacific Oysters Crassostreas gigas at Different Temperatures

The energy budgets, assimilation and conversion efficiency of 1-year-old-triploid Pacific oysters Crassostreagigas, were compared with those of sibling diploids to clarify the mechanism of energy metabolism. No significant difference was found between diploids and triploids in oxygen consumption. The net growth efficiencies of triploids and diploids were 37.4% and 33.9% respectively, and the gross growth efficiencies of them were 28.8% and 22.7%. The influence of ploidy and temperature on K1 was significant, but the variation of K2 may be attributable to ambient temperature. The ratio of gonad dry weight and dry tissue of triploids was 5%on average, and diploids about 25.6%. Our results showed that triploids, which do not reproduce and only have limited gonadal development, spend more energy for growth and more efficient in using energy than diploids do.

Food intake rates, assimilation efficiency, and transit times of Knysna (Tauraco corythaix) Turacos fed South African indigenous fruit

Fleshy-fruited plants and frugivores share a mutualistic relationship with plants offering the frugivores a reward of fleshy fruit pulp in order to disperse their seeds. However, all fruits are not equal in terms of energy available to frugivores. Consequently, we measured the assimilation efficiencies of fruits of six indigenous tree species for an avian frugivore, the Knysna Turaco (Tauraco corythaix). We predicted that the Turacos would process these indigenous fruits efficiently and have fast transit rates and high intake rates irrespective of species. Fruits were fed to the Turacos in separate trials to determine daily food and energy intake, assimilation efficiencies and digestive transit times. Digestive transit times of Knysna Turacos (c. 12–28 min) fall within the range of published examples for other frugivorous birds. Apparent assimilation efficiencies of the fruit ranged from c. 15–84% and were generally lower than those observed for other avian frugivores. Intake rates (in terms of wet weight) varied among the fruit species, and Knysna Turacos had greater intake rates on fruit which they are able to assimilate efficiently. Future studies looking at the nutritional composition of indigenous forest fruit may provide insight into the Knysna Turacos assimilation efficiency and consequently their food preferences and role as potential seed dispersers of fruiting tree species.

Effects of Diet on Growth-Related Patterns of Energy and Macronutrient Assimilation Efficiency in a Semi-Precocial Bird, the Gull-Billed TernGelochelidon nilotica

Albano N., Masero J.A., Sanchez-Guzman J.M., Villegas A. & Santiago-Quesada F. 2011. Effects of diet on growth-related patterns of energy and macronutrient assimilation efficiency in a semi-precocial bird, the Gull-billed Tern Gelochelidon nilotica. Ardea 99: 93–101.

Chemical composition and tissue energy density of the cuttlefish (Sepia apama) and its assimilation efficiency by Diomedea albatrosses

The cuttlefish Sepia apama Gray (Mollusca: Cephalopoda) is a seasonally abundant food resource exploited annually by moulting albatrosses throughout winter and early spring in the coastal waters of New South Wales, Australia. To assess its nutritional value as albatross forage, we analysed S. apama for water, lipid protein, ash contents, energy density and amino acid composition. Because albatrosses consistently consume S. apama parts preferentially in the order of head, viscera and mantle, we analysed these sections separately, but did not identify any nutritional basis for this selective feeding behaviour. The gross energy value of S. apama bodies was 20.9 kJ/g dry mass, but their high water content (>83%; cf <70% for fish) results in a relatively low energy density of 3.53 kJ/g. This may contribute to a need to take large meals, which subsequently degrade flight performance. Protein content was typically >75% dry mass, whereas fat content was only about 1%. Albatrosses feed on many species of cephalopods and teleost fish, and we found the amino acid composition of S. apama to be comparable to a range of species within these taxa. We used S. apama exclusively in feeding trials to estimate the energy assimilation efficiency for Diomedea albatrosses. We estimated their nitrogen-corrected apparent energy assimilation efficiency for consuming this prey to be 81.82 ± 0.72% and nitrogen retention as 2.90 ± 0.11 g N kg(-1) d(-1). Although S. apama has a high water content and relatively low energy density, its protein composition is otherwise comparable to other albatross prey species. Consequently, the large size and seasonal abundance of this prey should ensure that albatrosses remain replete and adequately nourished on this forage while undergoing moult.

Hepatic and renal cadmium accumulation is associated with mass-specific daily metabolic rate in the bank vole ( Clethrionomys glareolus)

Previous study has shown that photoperiod and age affect tissue accumulation of cadmium (Cd) in a small rodent, the bank vole. Since the body mass is also influenced by these factors, the present study was designed to determine whether mass-specific daily metabolic rate might be responsible for differential accumulation of Cd in the liver and kidneys of the short- and long-photoperiod bank voles as well as of the young and old animals. One- and five-month old male bank voles were held under short (8 h light / 16 h dark) or long (16 h light / 8 h dark) photoperiods and exposed to dietary Cd (100 μg/g) for 6 weeks. The bank voles raised under the short photoperiod and those injected subcutaneously with melatonin (7 μmol/kg/day) under the long photoperiod showed significantly higher concentrations of Cd in the liver (43–60%) and kidneys (40–47%) than the age-matched long-photoperiod animals. The old bank voles accumulated significantly less Cd in both organs than the young animals. These differences in Cd accumulation appeared not to be associated with the relative Cd intake. However, the hepatic and renal Cd levels followed a pattern similar to that of the mass-specific daily metabolic rate (or energy expenditure) and energy assimilation efficiency. These data indicate that mass-specific daily metabolic rate and energy assimilation efficiency (an indicative of digestive and absorptive processes) may be responsible for differential tissue Cd accumulation in the bank vole.

Effect of high-fat diet on body mass and energy balance in the bank vole

We tested the hypothesis that animals that reduce their body mass in response to decreased photoperiod do not develop diet-induced obesity (DIO) when fed a high-fat diet (HFD). Bank voles ( Clethrionomys glareolus) fed a diet with fat content of 13.5% by mass and 28.2% by energy, for 5 weeks, did not develop hyperphagia and were resistant to DIO, consistent with predictions. There was no significant difference between food (g/day) or energy intake (kJ/day) between the experimental or control group (fed a standard diet with fat content of 5.4% by mass and 12.3% by energy) over the duration of the experiment. However, as a result of a higher apparent energy assimilation efficiency (AEAE), voles fed the HFD assimilated significantly more energy over the 5-week period. Furthermore, they consumed twice as much fat per day as controls. There were no significant differences in resting metabolic rate (RMR) over time or between groups over the 5-week period. In conclusion, bank voles achieved resistance to DIO despite assimilating more energy than control animals fed the standard diet and taking in twice as much fat. Resistance did not occur by modification of RMR, implicating differences in activity levels.

The impact of lead on the assimilation efficiency of laboratory-held Diplopoda (Arthropoda) preconditioned in different environmental situations.

In five diplopod species from three families collected from locations with different soil metal contents, the following parameters were examined: the litter mass (and energy) ingested per day, the mass (and energy) assimilation rates, and the litter mass (and energy) assimilated per day, when the diplopods were fed (1) uncontaminated and (2) artificially lead-enriched leaf litter. These parameters were compared between species and between animals from different sites. The mass and energy assimilation efficiencies depend on (1) the size of the species and (2) the collection site of the animals. Relative mass (and in three of the species examined also energy) assimilation was highest in those animals collected from the less contaminated sites. With artificial diets, specimens from a site with soil contaminated by heavy metals showed greater assimilation of both mass and energy than originally unaffected specimens. One species (Glomeris conspersa) was able to compensate for the low assimilation rate by increased consumption, and thus guarantee a sufficient energy supply. One of the other species (Polydesmus denticulatus), however, did not show this compensation. Animals of this species from less contaminated sites showed a very low absolute energy assimilation rate and high mortality under lead treatment.

Energy Requirements of Nestling Cape Vultures

A continuous feeding trial was used to determine Gross Energy Intake (GEI), Metabolizable Energy (ME) and energy Assimilation Efficiency (AE) during growth of captive (hand-reared) nestling Cape Vultures. The mean ash-free dry energy density of daily samples of excreta for the nestlings was 14.8 ? 0.4 kJ/g (range 14.2-15.9 kJ/g). Nestling GEI increased from shortly after hatching to reach a maximum of 6,443.3 + 388.9 kJ/day between 8085 days. After 85 days, GEI decreased to adult levels (range 2,734-3,639 kJ/day) between 105 days and fledging (136 days of age). AE of hand-reared nestlings ranged between 82% and 92%. Mean GEI during the period of maximum growth between 60 and 100 days was 5,459.6 + 529.8 kJ/day. If deprived of food, a 62-day old nestling with a one kilogram fat reserve (about 15% of body mass) would theoretically deplete this energy reserve in about eight days, if growth continued at a normal rate.

Resource Utilization by Desert Quail: Time and Energy, Food and Water

Time—energy budgets (TEB) of Gambel's Quail (Callipepla gambelii) were compiled during two summers in the Colorado Desert of California. Quail spent 6.77 h/d foraging, 6.2 h/d inactive during daylight hours, and 11.02 h/d inactive at night. Field metabolic rate (FMR) calculated from this activity budget was 81.8 kJ/d. Of this, 47.3 kJ/d was expended during foraging, 12.6 kJ/d in daytime inactivity, and 20.4 kJ/d in nighttime inactivity. Despite the extremely hot thermal environment (maximum ambient temperature °45°C), there was no energy cost above resting levels for thermoregulation. FMR was also measured simultaneously with doubly labeled water (DLW), and averaged 90.8 kJ/d. TEB and DLW values agreed to within 6% when differences in measurement period were taken into account. A laboratory validation study indicated that DLW and balance methods agreed to within 5%. The FMR of C. gambelii was only 40% of that predicted for a bird of its body mass. This low FMR is primarily the result of a low resting metabolic rate (RMR): 51% of the predicted basal rate in 1981, and 70% of predicted in 1982. The basis and significance of this low and variable RMR are unclear. Energy assimilation efficiency, measured in laboratory feeding experiments with a mixed seed and arthropod diet, was 60.3%. An individual quail in the field thus required 150.3 kJ/d in its diet, representing a dry matter intake of 8.1 g/d. A diet of seeds alone provides insufficient water for Gambel's Quail in summer, so they must either incorporate moist food items in their diet or drink free water. It was calculated that over the course of a year, a population of Gambel's Quail consumes seeds with a total energy content °15% as great as that in seeds consumed by a population of desert rodents or harvester ants in the same area. Gambel's Quail thus may be important factors in the competition for resources among desert granivores, particularly because they can eat one of their competitors (harvester ants).

Gastric emptying and the return of appetite in juvenile turbot, Scophthalmus maximus L., fed on artificial diets

Gastric emptying time in Scophthalmus maximus, when fed friable artificial pellets based on fishmeal, is composed of two phases:(a) a delay time (td) during which the meal forms a bolus and which shortens with temperature, and(b) an emptying phase (duration tend) which varies with meal size (S), body weight (W) and temperature (71 according to: image (where tend is in h, S is in g, W is in g and T is °C). During the emptying phase, stomach contents decrease curvilinearly according to: image (where St, &amp; So is in g and t is in h) in which the instantaneous digestion rate, K, varies with fish weight and temperature as: image Food pellets were prepared which remained separate and did not form a bolus in the stomach; K increased if a given meal size was subdivided to increase surface area. If meal size was increased by ingestion of identical pellets, K decreased. After a satiation meal, appetite in young turbot returns in direct relation to the degree of stomach emptiness. When food is regularly available, young turbot feed steadily at a rate which maintains their stomachs at c. 85% maximum fullness. When trained to use demand feeders, the fish interact as a group to feed rhythmically, but feeding rate falls 33% to only two‐thirds of the previous rate since stomach fullness, and hence digestion rate (g h−1), is maintained at a lower level. Reduction in dietary energy density below 1 kCal g−1 increases gastric emptying rate and the turbot demonstrate partial compensation by increasing food intake. On energy‐rich diets, protein nitrogen and energy assimilation efficiencies remain high (97 5% and 91% respectively) irrespective of feeding rate and frequency.

Altered Energy Metabolism in an Irradiated Population of Lizards at the Nevada Test Site

Field metabolic rates (via doubly labeled water), body compartmentalization of energy stores, and energy assimilation efficiencies were measured to assess all avenues of energy utilization in Uta stansburiana living in a low-level gamma-irradiated plot in Rock-Valley, Nevada. Comparison of energy budgets for radiation-sterilized females with those of nonirradiated control lizards revealed several substantial differences. Sterile females were heavier, mainly because they had extraordinarily large energy (fat) storage depots. Sterile females had much lower rates of energy expenditure via respiration and lower rates of energy intake by feeding. These differences are interpreted as indirect responses to radiation-induced sterility. Gastrointestinal tract function in sterile females was normal. There is little evidence of direct radiation effects on physiological functions other than reproduction.

Food and energy requirements of captive barn owls Tyto alba

1. 1. Food and energy requirements of captive barn owls were determined at 5, 15 and 25°C. 2. 2. Food consumption, gross energy intake, dry matter intake, and existence metabolism increased as ambient temperature decreased. 3. 3. Barn owl energy assimilation efficiencies at the three test temperatures were approximately 78%. 4. 4. An increase in bioenergetic parameters might be anticipated when a bird is cold-stressed and must increase its metabolism for thermoregulation.

Energy Assimilation, Nitrogen Requirement, and Diet in Free-Living Antelope Ground Squirrels Ammospermophilus leucurus

Antelope ground squirrels (Ammospermophilus leucurus, 80-100 g) consumed vegetation, seeds, arthropods, and vertebrate flesh throughout the year in the Mojave Desert near Barstow, California. Apparent energy assimilation efficiency (100 x $[kJ_{food} - kJ_{feces}]/kJ_{food}$) on each type of food ranged from 55% on mature plant leaves to ~90% on vertebrate flesh and seeds. Apparent assimilation of nitrogen (N) ranged from 63% on plant fruiting parts to 87% on arthropods. For the foods studied here, antelope ground squirrels apparently assimilated as much of the energy and N in their food as do other rodents, even those that specialize on some of these food types. However, an important difference between omnivorous rodents, such as A. leucurus, and herbivorous rodents may be the ability of the latter to survive on diets with lower dry-matter digestibilities. The N requirements of free-living A. leucurus were estimated based on a feeding trial with captives fed a protein-free diet. The results suggested tha...

Food Consumption and Energy Requirements of Captive Bald Eagles

Thirty-six food consumption trials were conducted using 4 captive winter-acclimatized bald eagles (Haliaeetus leucocephalus) on 3 diets at 3 temperatures. Daily consumption for combined temperatures was highest on the chum salmon (Oncorhynchus keta) diet (92.0 g/kg), intermediate on the blacktailed jack rabbit (Lepus californicus) diet (74.8 g/kg), and lowest for mallard ducks (Anas platyrhynchos) (65.1 g/kg) which was inversely related to the wet energy contents (0.90, 1.22, and 1.96 kcal/g, respectively) of the diets. Dry matter, fat, protein, and ash contents accounted for the disparity in wet energy content. Daily gross energy intake, existence metabolism, and excretory energy for all diets combined were 116.9, 94.3, and 22.5 kcal/kg at -10 C, 101.8, 81.8, and 20.0 kcal/kg at 5 C, and 89.7, 69.1, and 20.6 kcal/kg at 20 C, respectively. Energy assimilation efficiencies were higher on the duck diet (85.2%) compared to salmon (75.0%) and rabbit (75.4%) and efficiency increased with decreasing temperature on the latter 2 diets. Minimal gross energy requirements of a 4.5-kg eagle for a 90-day winter period at 5 C is predicted to be 13 salmon, 20 rabbits, or 32 ducks. J. WILDL. MANAGE. 46(3):646-654 Wintering bald eagles are opportunistic scavengers and predators and range widely to locate food. Fish is the main food source, but waterfowl, seabirds, small mammals, and carrion are eaten as alternate prey (Spencer 1976). Winter diets of this species have been assessed in many regions (Imler and Kalmbach 1955, Spencer 1976, Steenhof 1978), but food requirements have received little attention. Food consumption by captive bald eagles was measured by Chura and Stewart (1967) and Duke et al. (1976) incidental to other experiments. Stewart (1970) documented food needs of a single, captive bald eaglet. Energy consumption has not been studied. Some information is available on food requirements of white-tailed eagles (Haliaeetus albicilla) (Love 1979) and golden eagles (Aquila chysaetos) (Fevold and Craighead 1958, Brown and Watson 1964, McGahan 1967, Collopy 1980). Hayes and Gessaman (1980) reported the effects of temperature, wind, and radiation on the e ergy metabolism of the golden eagle. Winter raptor populations are often food-limited (Newton 1979:80). Starvation may be a population-regulating mechanism for some bald eagle populations (Sherrod et al. 1977). Management practices are currently being developed that include preservation and enhancement of the food base with the goal of increased winter survival (Stalmaster 1980). Additional information on the food and energy requirements of wintering bald eagles is necessary for predicting carrying capacities of wintering areas, to understand impacts on prey populations, and in estimating food supply needs for artificial feeding programs. This study measured food and energy consumption and energy assimilation of 4 captive bald eagles on 3 common diets at 3 temperatures. Partial funding was provided by the Department of Biology and Ecology Center at Utah State University and the Washington Department of Game. W. English and J. W. Foster provided the I Present address: 10,000 47th Ave. S.W., Seattle, WA 98146. 646 J. Wildl. Manage. 46(3):1982 This content downloaded from 157.55.39.35 on Wed, 31 Aug 2016 04:32:15 UTC All use subject to http://about.jstor.org/terms BALD EAGLE FOOD AND ENERGY REQUIREMENTS. Stalmaster and Gessaman 647 experimental animals. R. L. Knight assisted in many aspects of this study. L. C. Stoddart and R. M. Stalmaster supplied food items. K. L. Hamilton and J. S. Kirkley assisted in handling eagles. We appreciate review comments of M. R. Fuller, J. W. Grier, K. L. Hamilton, J. R. Murphy, and J. R. Newman on an earlier draft of this paper.