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Background: Meniscus lesions are common musculoskeletal knee injuries which often lead to pain, limitation and compensations during functional tasks, such as descending stairs. This study investigated the effect of patellar taping with tension and without tension on three-dimensional (3D) kinematics of the knee during a slow step descent task in patients with meniscal lesions., Methods: Ten patients diagnosed with a meniscal lesion, confirmed by magnetic resonance imaging, underwent five, step descent movements at slow speed under three different conditions: 1) no taping; 2) tension-free taping; and 3) patellar taping with medial tension. 3D kinematic data were recorded from the injured knee using an eight-camera infrared Vicon motion analysis system. Maximum and minimum angle values and total range of motion (maximum/minimum value) in three movement planes during single-limb stance were compared using a repeated measure ANOVA., Findings: Results showed a significant increase in the maximum and minimum angle value in the sagittal plane (mean differences=2.4° and 4.2°, respectively) and a decrease in the transverse plane (-6.3° and -2.2°, respectively) for the patellar taping condition compared to the no taping condition. A decreased rotational angle range when comparing the patellar taping to the no taping (-4.1°) and tension-free taping (-3.1°) conditions was also observed. These changes remained significant when pain was considered as a covariate in the analysis. The tension applied to the patellar tape played a role in controlling the sagittal and transverse plane step-down movement among patients in our study., Interpretation: These results support the use of patellar taping with a medially oriented tension to help to reduce the transversal plane movement of the knee in this population and they bring new light to the taping effect., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Ultrasonography has proven to be a valuable noninvasive method of measure of muscle size in birds, but validation of its use in birds as small as black-capped chickadees (Poecile atricapillus; 11 g) is scarce. The effect of observers and life state (dead or alive) of models used for calibration on measurement quality is also poorly documented. Using 31 dead and 22 live chickadees, linear regressions between ultrasound and dissection measurements of pectoral and thigh muscles were fitted and compared between five different observers. R(2) values varied greatly between observers and were generally weaker in live birds, ranging between 0.02 and 0.59, despite high repeatability of measurement. Using equations calculated from dead birds to estimate muscle mass of live birds yielded much higher measurement errors (9%-18%) than when using equations calculated from live birds (5%-8%). Our results suggest that with careful training and using only calibration from live birds, ultrasonography can be a useful but limited tool to estimate muscle size of birds as small as the black-capped chickadee.

Resident passerines inhabiting high latitude environments are faced with strong seasonal changes in thermal conditions and energy availability. Summit metabolic rate (maximal metabolic rate elicited by shivering during cold exposure: M(sum)) and basal metabolic rate (BMR) vary in parallel among seasons and increase in winter due to cold acclimatization, and these adjustments are thought to be critical for survival. Wintering individuals expressing consistently higher M(sum) and BMR could therefore be seen as better performers with higher chances of winter survival than those exhibiting lower metabolic performance. In this study, we calculated repeatability to evaluate temporal consistency of body mass, BMR and M(sum) within and across three consecutives winters in black-capped chickadees (Poecile atricapillus). We found that body mass was significantly repeatable both within and across winters (R 0.51-0.90). BMR (R 0.29-0.47) was only repeatable within winter while M(sum) was repeatable both among (R 0.33-0.49) and within winters (R 0.33-0.49) with the magnitude and significance of repeatability in both variables depending on the year and whether they were corrected for body mass or body size. The patterns of repeatability observed among years also differed between the two variables. Our findings suggest that the relative ranking of individuals in winter metabolic performance is affected by local ecological conditions and can change within relatively short periods of time., (© 2015 Wiley Periodicals, Inc.)

Reproductive success of seabirds is tightly associated with availability of their prey for which the spatiotemporal distribution may be influenced by sea surface temperature (SST) fluctuations. The objective of this study was to investigate whether Northern gannets (Morus bassanus) from the largest colony in North America (Bonaventure Island, Quebec, Canada) were in negative nutritional state during the unprecedented low reproductive success year of 2012, and whether this was associated with changes in SST anomalies and diet. The incubation period of gannets in 2012 was characterized by a significant decline, from early to late incubation, in plasma triglyceride levels that was associated with an increase in plasma corticosterone levels. However, no changes in plasma glycerol and β-hydroxybutyrate levels were noted. SST anomalies recorded in this area (south of the Gulf of St. Lawrence) during the breeding period were consistently higher in 2012 compared to the previous year (a better reproductive success year). Based on signatures of stable carbon (δ(13)C) and nitrogen (δ(15)N) isotopes in gannet red blood cells and in whole fish homogenates of three major preys (mackerel, herring, and capelin), a minor dietary shift was noted between those years and incubation periods. In light of these findings, it is suggested that the extreme warm-water perturbation event that prevailed in the Gulf of St. Lawrence during summer 2012 was associated with a rapid deterioration of nutritional condition of Bonaventure Island gannets during the incubation. These suboptimal physiological changes likely contributed to the dramatic decline in reproductive success reported in this colony., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Reaction norms reflect an organisms' capacity to adjust its phenotype to the environment and allows for identifying trait values associated with physiological limits. However, reaction norms of physiological parameters are mostly unknown for endotherms living in natural conditions. Black-capped chickadees (Poecile atricapillus) increase their metabolic performance during winter acclimatization and are thus good model to measure reaction norms in the wild. We repeatedly measured basal (BMR) and summit (Msum) metabolism in chickadees to characterize, for the first time in a free-living endotherm, reaction norms of these parameters across the natural range of weather variation. BMR varied between individuals and was weakly and negatively related to minimal temperature. Msum varied with minimal temperature following a Z-shape curve, increasing linearly between 24°C and -10°C, and changed with absolute humidity following a U-shape relationship. These results suggest that thermal exchanges with the environment have minimal effects on maintenance costs, which may be individual-dependent, while thermogenic capacity is responding to body heat loss. Our results suggest also that BMR and Msum respond to different and likely independent constraints.

Plasma lipid metabolites triglycerides (TRIG) and glycerol (GLY) are used as indicators of fattening rate and nutritional condition in migratory birds. Requiring only one blood sample, they could also be used for studying daily and seasonal fattening rates in relation with habitat quality or weather variations in species wintering in cold climates. Using black-capped chickadees exposed to three experimental temperatures (0 °C, 15 °C, and 30 °C), the goal of this experiment was to determine the relationship between plasma levels of TRIG and GLY and fattening rate measured over periods from a few hours to the previous two days. Results showed that birds maintained in the cold had metabolite levels 39-81% higher than those at thermoneutrality, likely reflecting the size of their fat reserves, and that TRIG and total GLY were highly correlated across treatments. Fattening rate was also higher at 0 °C (+35%) and 30 °C (+24%) relative to that measured at 15 °C and, as expected, was positively correlated with metabolite levels across treatments. However, despite fattening rates similar to that observed at the other temperatures, the relationships were uncoupled at 30 °C, implying that the technique may not be easily applicable at temperatures within or close to thermoneutrality. We also found a strong individual effect in the relationships between fattening rate and TRIG levels, suggesting high individual consistency in these parameters in conditions of unrestricted food access such as in captivity. Our study confirms that plasma TRIG and GLY levels can be used as relative indexes of condition and fattening rates in wintering passerines., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Abstract Small avian species wintering at northern latitudes typically show increases in basal metabolic rate (BMR) and maximal thermogenic capacity (Msum). Those are widely assumed to reflect changes in body composition, with enlargement of digestive and excretory organs resulting in elevated winter BMR and larger body muscles driving the increase in Msum. Using free-living black-capped chickadees (Poecile atricapillus) as our model species, we investigated seasonal changes in body composition and tested for relationships between mass variations of body organs and variability of both BMR and Msum. Our results confirmed the expected winter increase in mass of body muscles and cardiopulmonary organs (heart + lungs) and showed that 64% of the observed Msum variations throughout the year were explained by changes in these organs. In contrast, we found little support for an effect of the digestive organs (gizzard + intestines) on BMR seasonal changes. Instead, this variable was mainly influenced by variations in mass of body muscles and excretory organs (liver + kidney), explaining up to 35% of its variability.

In small resident bird species living at northern latitudes, winter cold acclimatization is associated with an increase in pectoral muscle size and haematocrit level, and this is thought to drive the seasonal increase in summit metabolic rate (Msum, a measure of maximal shivering thermogenic capacity). However, evidence suggesting that pectoral muscle size influences Msum is correlational and the link between haematrocrit level and Msum remains to be demonstrated. We experimentally tested the relationship between pectoral muscle size and Msum by manipulating muscle size using a feather clipping protocol in free-living wintering black-capped chickadees (Poecile atricapillus). This also allowed us to investigate the link between haematocrit and thermogenic capacity. After a first series of measures on all birds, we cut half of the flight feathers of experimental individuals (N=14) and compared their fat and pectoral muscle scores, Msum and haematocrit level at recapture with their previous measures and with those of control birds (N=17) that were captured and recaptured at comparable times. Results showed that: (1) experimental birds developed larger pectoral muscles than control individuals and (2) mass-independent Msum was up to 16% higher in birds expressing large pectoral muscles. Msum was also positively correlated with haematocrit, which was not affected by the experimental manipulation. These findings demonstrate that, for a given body mass, large pectoral muscles are associated with a higher Msum in black-capped chickadees and that oxygen carrying capacity likely supports thermogenesis in this species.

Stochastic winter weather events are predicted to increase in occurrence and amplitude at northern latitudes and organisms are expected to cope through phenotypic flexibility. Small avian species wintering in these environments show acclimatization where basal metabolic rate (BMR) and maximal thermogenic capacity (MSUM) are typically elevated. However, little is known on intra-seasonal variation in metabolic performance and on how population trends truly reflect individual flexibility. Here we report intra-seasonal variation in metabolic parameters measured at the population and individual levels in black-capped chickadees (Poecileatricapillus). Results confirmed that population patterns indeed reflect flexibility at the individual level. They showed the expected increase in BMR (6%) and MSUM (34%) in winter relative to summer but also, and most importantly, that these parameters changed differently through time. BMR began its seasonal increase in November, while MSUM had already achieved more than 20% of its inter-seasonal increase by October, and declined to its starting level by March, while MSUM remained high. Although both parameters co-vary on a yearly scale, this mismatch in the timing of variation in winter BMR and MSUM likely reflects different constraints acting on different physiological components and therefore suggests a lack of functional link between these parameters.

Winter requires physiological adjustments in northern resident passerines. Cold acclimatization is generally associated with an increase in physiological maintenance costs, measured as basal metabolic rate (BMR), and cold endurance, reflected by summit metabolic rate (M(sum)). However, several northern species also form social groups in winter and a bird's hierarchical position may influence the size of its metabolically active organs as well as its BMR. Winter metabolic performance in these species may therefore reflect a complex set of adjustments to both seasonal climatic variations and social environment. We studied the effect of social status on parameters of cold acclimatization (body mass, size of fat reserves and pectoral muscles, BMR and M(sum)) in free-living black-capped chickadees (Poecile atricapillus). Birds that were structurally large and heavy for their body size, mostly dominant individuals, carried more fat reserves and had larger pectoral muscles. However, social status had little effect on metabolic performance in the cold. Indeed, M(sum) was independent of social rank while mass-corrected BMR was slightly lower in dominant individuals, likely due to a statistical dilution effect caused by large metabolically inactive fat reserves. BMR and M(sum), whether considered in terms of whole-animal values, corrected for body mass or body size were nevertheless correlated, suggesting a functional link between these metabolic components. Our results therefore indicate that the energy cost of social dominance is not a generalized phenomenon in small wintering birds.

Phenotypic flexibility in shorebirds has been studied mainly in the context of adjustments to migration and to quality of food; little is known on how birds adjust their phenotype to harsh winter conditions. We showed earlier that red knot (Calidris canutus islandica) can acclimate to cold by elevating body mass. This goes together with larger pectoral muscles, i.e., greater shivering machinery, and thus, better thermogenic capacity. Here, we present results of a yearlong experiment with indoor captive knots to determine whether this strategy is part of their natural seasonal phenotypic cycle. We maintained birds under three thermal regimes: constant cold (5 °C), constant thermoneutrality (25 °C) and natural seasonal variation between these extremes (9-22 °C). Each month we measured variables related to the birds' endurance to cold and physiological maintenance [body mass, thickness of pectoral muscles, summit metabolic rate (M(sum)), food intake, gizzard size, basal metabolic rate (BMR)]. Birds from all treatments expressed synchronized and comparable variation in body mass in spite of thermal treatments, with a 17-18% increase between the warmest and coldest months of the year; which appeared regulated by an endogenous driver. In addition, birds living in the cold exhibited a 10% higher average body mass than did those maintained at thermoneutrality. Thickness of the pectoral muscle tracked changes in body mass in all treatments and likely contributed to greater capacity for shivering in heavier birds. Consequently, M(sum) was 13% higher in cold-acclimated birds compared to those experiencing no thermoregulation costs. However, our data also suggest that part of maximal heat production comes from nonshivering processes. Birds facing cold conditions ate up to 25% more food than did birds under thermoneutral conditions, yet did not develop larger gizzards. Seasonal variation in BMR followed changes in body mass, probably reflecting changes in mass of metabolically active tissues. Just as cold-exposed birds, red knots in the variable treatment increased body mass in winter, thereby improving cold endurance. During summer, however, they maintained a lower body mass and thermogenic capacity compared to cold-exposed birds, similar to individuals kept at thermoneutrality. We conclude that red knots acclimate to seasonal variations in ambient temperature by modulating body mass, combining a preprogrammed increase in mass during winter with a capacity for fine-tuning body mass and thermogenic capacity to temperature variations.

Pre-flight fuelling rates in free-living red knots Calidris canutus, a specialized long-distance migrating shorebird species, are positively correlated with latitude and negatively with temperature. The single published hypothesis to explain these relationships is the heat load hypothesis that states that in warm climates red knots may overheat during fuelling. To limit endogenous heat production (measurable as basal metabolic rate BMR), birds would minimize the growth of digestive organs at a time they need. This hypothesis makes the implicit assumption that BMR is mainly driven by digestive organ size variation during pre-flight fuelling. To test the validity of this assumption, we fed captive knots with trout pellet food, a diet previously shown to quickly lead to atrophied digestive organs, during a fuelling episode. Birds were exposed to two thermal treatments (6 and 24 degrees C) previously shown to generate different fuelling rates in knots. We made two predictions. First, easily digested trout pellet food rather than hard-shelled prey removes the heat contribution of the gut and would therefore eliminate an ambient temperature effect on fuelling rate. Second, if digestive organs were the main contributors to variations in BMR but did not change in size during fuelling, we would expect no or little change in BMR in birds fed ad libitum with trout pellets. We show that cold-acclimated birds maintained higher body mass and food intake (8 and 51%) than warm-acclimated birds. Air temperature had no effect on fuelling rate, timing of fuelling, timing of peak body mass or BMR. During fuelling, average body mass increased by 32% while average BMR increased by 15% at peak of mass and 26% by the end of the experiment. Our results show that the small digestive organs characteristic of a trout pellet diet did not prevent BMR from increasing during premigratory fuelling. Our results are not consistent with the heat load hypothesis as currently formulated.

Recent studies have shown that the metabolic cost of avian egg production involves a 16-27% increase in metabolic rate (MR) above non-reproductive basal or resting values (BMR and RMR, respectively). To determine how the metabolic cost of egg production interacted with the costs of other essential processes (such as cold acclimation and active heat production), we measured the MR of non-breeding and egg-producing zebra finches (Taeniopygia guttata) while (a) warm-acclimated (to 19-21 degrees C) and measured within their thermoneutral zone (at 35 degrees C), (b) cold-acclimated (to 7 degrees C) and measured at thermoneutrality (at 35 degrees C, i.e. not actively producing heat), and (c) cold-acclimated and measured below thermoneutrality (at 7 degrees C) (i.e. during active heat production). The metabolic cost of egg production was small (24% above BMR) compared with the additive costs of cold acclimation and active heat production (224% above BMR). Exposure to low ambient temperatures was accompanied by an increase in seed consumption (by 72%) and a decrease in locomotor activity (by 72%) compared with warm-acclimated, non-breeding values. By contrast, egg production in heat-producing females was associated with an 11% decrease in MR and a 22% decrease in seed consumption compared with non-breeding thermoregulating values. Our data suggest that while the increase in MR associated with egg production is small in relation to the birds' capacity to increase MR in response to other energetically demanding processes, the addition of egg production to these metabolically costly activities may be enough to necessitate the use of energy-saving strategies, such as internal energy reallocation, to cope with the additional energetic demands.

Previous experiments showed reduction of basal metabolic rate (BMR) in birds facing energetic challenges. We alternately exposed two groups of red knots (Calidris canutus) to either 6 h or 22 h of food availability for periods of 22 d. Six h of access to food led to a 6%-10% loss of body mass over the first 8 d, with nearly all of the birds' daily energy expenditures supported by body nutrient stores during the first 2 d. Birds responded by increasing feeding behavior and food intake, but the response was slow. There were no gains of mass before day 15, which suggests a digestive bottleneck and a period of physiological adjustment. Food-restricted birds exhibited decreases in pectoral-muscle thickness and BMR in association with a loss of body mass. Although a decrease in BMR saves energy, savings represented only 2%-7% of the daily energy spent in excess of that acquired during the deficit period. Red knots did not downregulate mass-independent BMR. On the bases of recent independent findings and the pattern of mass gain observed when food access was switched from 6 h to 22 h, we suggest that these birds routinely maintain nutrient stores as a buffer against periods of energy shortages, thereby precluding the need for downregulation of mass-independent BMR.

In response to unbalanced energy budgets, animals must allocate resources among competing physiological systems to maximize fitness. Constraints can be imposed on energy availability or energy expenditure, and adjustments can be made via changes in metabolism or trade-offs with competing demands such as body-mass maintenance and immune function. This study investigates changes in constitutive immune function and the acute-phase response in shorebirds (red knots) faced with limited access time to food. We separated birds into two experimental groups receiving either 6 h or 22 h of food access and measured constitutive immune function. After 3 wk, we induced an acute-phase response, and after 1 wk of recovery, we switched the groups to the opposite food treatment and measured constitutive immune function again. We found little effect of food treatment on constitutive immune function, which suggests that even under resource limitation, a baseline level of immune function is maintained. However, birds enduring limited access to food suppressed aspects of the acute-phase response (decreased feeding and mass loss) to maintain energy intake, and they downregulated thermoregulatory adjustments to food treatment to maintain body temperature during simulated infection. Thus, under resource-limited conditions, birds save energy on the most costly aspects of immune defense.

Basal metabolic rate (BMR) in animals is interpreted as reflecting the size and metabolic intensity of energy-consuming tissues. However, studies investigating relationships between the mass of specific organs and interindividual variation in BMR have produced inconsistent patterns with regard to which organs have the largest impact on BMR variation. Because of the known flexibility in organ mass and metabolic intensity within individual organs, relationships between BMR and body-composition variables are bound to be context specific. Altricial nestlings are excellent models to illustrate this phenomenon because of the extreme variation in body composition occurring during growth. Using European starlings at three age classes, we studied changes in body composition together with its effect on variation in resting metabolic rate (RMR) in order to highlight the context-specific nature of these relationships. Our data suggest a transition in metabolic costs during growth in starling nestlings. During the linear phase of growth, energy is mainly consumed by tissue-synthesis processes, with fast-growing organs having a large influence on RMR. In the plateau phase of growth, the energy expenditure is transferred to functional costs, with high-intensity organs having a predominant effect on RMR variation. Our data illustrates the context-specific nature of organ mass-metabolic rate correlations, which complicates inter- and intraspecific comparisons of BMR. In the future, such comparisons must be done while taking the physiological state of the study animal into account.

It is axiomatic that whole-animal metabolism, measured for example as daily energy expenditure (DEE), plays a central role in determining reproductive success and survival (fitness) in all organisms. Nevertheless, strong evidence for consistent systematic relationships between DEE and either individual traits (age, sex, body size), environmental factors (e.g. food availability, temperature) or 'fitness' traits (e.g. number of offspring, survival) remains far from compelling in birds and mammals. Recently, we suggested that female birds might utilise complex, individually variable energy management strategies to meet the metabolic demands of reproduction, generating a wide spectrum of effects on reproductive DEE, from overcompensation (net decrease in DEE) to additive effects (net increase in DEE). Here we show that this individually variable adjustment or 'plasticity' in energy expenditure associated with egg production is repeatable among individuals between successive breeding attempts in female zebra finches (Taeniopygia guttata). Our study highlights the importance (a) of measuring 'plasticity' or change associated with transitions of physiological state (e.g. non-breeding to breeding) based on multiple measurements of the same individual, and (b) of extending consideration of how selection might drive the evolution of phenotypic plasticity per se to include physiological and metabolic traits.

Even though molt involves both endocrine and energetic changes in bird bodies, this study is among the first to combine assessments of energy costs together with thyroid hormone variations in molting birds. Individual shorebirds (red knots Calidris canutus islandica) were measured while in full summer and winter plumage as well as during peak of molt. Molt was associated with a 9.8% increase in average mass-independent basal metabolic rate (BMR) above nonmolting levels. Individual plasma levels of thyroxine (T(4)) were correlated with individual rate of body feather renewal, confirming that T(4) is related to body molt but also showing that it is potentially regulating its rate. Across seasons, mass-independent average heat loss measured as conductance gradually declined with conductance during molt falling between measured values for summer and winter. During the molting period, however, body molting rate was positively correlated with thermal conductance, indicating that for a given ambient temperature below thermoneutrality, the fastest molting birds were losing more body heat. Across seasons, triiodothyronine (T(3)), a hormone typically upregulated in response to a cold stimulus, was correlated with individual thermal conductance and BMR. We suggest that the increased heat loss of fast-molting birds leads to a cold-acclimatization response that may be partly responsible for the elevated BMR measured during molt. This could be mediated through a stimulatory effect of T(3) on BMR in response to increased heat loss. Our interpretation is supported by a positive relationship between the individual changes in conductance and the change in BMR from summer to the molting period.

In the calidrine sandpiper red knot (Calidris canutus), the weeks preceding takeoff for long-distance migration are characterized by a rapid increase in body mass, largely made up of fat but also including a significant proportion of lean tissue. Before takeoff, the pectoral muscles are known to hypertrophy in preparation for endurance flight without any specific training. Because birds facing cold environments counterbalance heat loss through shivering thermogenesis, and since pectoral muscles represent a large proportion of avian body mass, we asked the question whether muscle hypertrophy in preparation for long-distance endurance flight would induce improvements in thermogenic capacity. We acclimated red knots to different controlled thermal environments: 26 degrees C, 5 degrees C, and variable conditions tracking outdoor temperatures. We then studied within-individual variations in body mass, pectoral muscle size (measured by ultrasound), and metabolic parameters [basal metabolic rate (BMR) and summit metabolic rate (M(sum))] throughout a 3-mo period enclosing the migratory gain and loss of mass. The gain in body mass during the fattening period was associated with increases in pectoral muscle thickness and thermogenic capacity independent of thermal acclimation. Regardless of their thermal treatment, birds showing the largest increases in body mass also exhibited the largest increases in M(sum). We conclude that migratory fattening is accompanied by thermoregulatory side effects. The gain of body mass and muscle hypertrophy improve thermogenic capacity independent of thermal acclimation in this species. Whether this represents an ecological advantage depends on the ambient temperature at the time of fattening.

Marked interindividual variation in metabolic rate suggests considerable complexity in energy management strategies, but attempts to further our understanding of the relationship between resting metabolic rate (RMR), daily energy expenditure (DEE), and reproductive effort have been hampered by the complexity of studying this system in the field. Here, we describe energy management strategies in a captive-breeding system, using Zebra Finches (Taeniopygia guttata), to demonstrate the high level of complexity and interindividual variability in energy expenditure, food intake, locomotor activity, and reproductive effort. In particular, we investigated whether the increase in RMR associated with egg production is additive, resulting in higher DEE and a need for elevated food intake, or whether this cost is compensated by reduced expenditure in nonreproductive components of the energy budget. We found high levels of intra-individual variation in energy expenditure associated with egg production in female Zebra Finches, e.g., comparing nonbreeding stage with the one-egg stage, change in RMR varied from 4.0% and 41.3%, and change in DEE varied from -33.3% to +46.4%. This variation was systematically related to aspects of locomotor activity and reproductive effort. Females with the largest increase in RMR during egg production decreased locomotor activity the most but still had increased DEE at the one-egg stage, and females with high DEE at the one-egg stage produced larger clutches. Our study suggests that females minimize increases in DEE during egg production through behavioral energy reallocation (reduced locomotor activity) but that individuals differ in their use of this strategy, which, in turn, is related to the absolute level of reproductive investment. This suggests a very complex, individually variable system of energy management to meet the demands of egg production.

The metabolic cost of egg production in birds (passerines) has been measured as a 16-27% increase in basal or resting metabolic rate (BMR and RMR, respectively) when comparing non-breeding values with those in egg-producing individuals. However, available data to date have been obtained in free-living birds and may thus be confounded by the effect of variable ecological conditions on non-reproductive physiological machinery (organ mass or metabolic activity) which might contribute to measured variation in RMR. Here, we show that in captive, controlled conditions, the process of egg formation induces a 22% increase in RMR in female zebra finches Taeniopygia guttata. Among individuals, variation in laying RMR is independent of egg mass, clutch size or total clutch mass. Importantly, we show that individual variation in both non-breeding and laying RMR is repeatable over periods of at least 8-10 months, i.e. individual variation in RMR remained constant over time for any given physiological state. This suggests that the metabolic cost of egg formation should respond to selection. However, we also show that in males, but not females, repeatability of RMR declines over time even when birds are kept in constant controlled conditions.

Current research in birds suggests that a conflict should exist during reproduction for the role of the glucocorticoid corticosterone (CORT). While elevated levels have been correlated with the increased energetic demand of raising offspring, elevated CORT levels have traditionally been implicated in reproductive abandonment. We examined the relationship between CORT and nest desertion in breeding wild female European starlings (Sturnus vulgaris) incorporating analyses of both total circulating levels and 'free', unbound CORT through analysis of corticosteroid-binding globulin (CBG). Free baseline CORT levels of nest-abandoning birds were significantly higher than nonabandoning birds within each stage, with chick-rearing birds exhibiting the highest free baseline CORT levels, while concurrently remaining the most resistant stage to nest desertion. Elevated free baseline CORT levels in chick-rearing birds were not due to increased total CORT secretion, but rather to a decrease in CBG levels. Overall, our results suggest that CORT and CBG interact to play a role in mediating the increased energetic demand of offspring, while minimizing the chances of nest desertion, thereby alleviating any potential behavioral conflict for CORT during reproduction. Furthermore, these results demonstrate that the traditional view of the role of CORT during reproduction is much more complex than previously appreciated. Together with mounting evidence, we suggest that elevated corticosteroid levels are an inherent and necessary part of reproduction in nonmammalian tetrapods.

Little is known about the energy costs of egg production in birds. We showed in previous papers that, during egg production, European starlings (Sturnus vulgaris) undergo a 22% increase in resting metabolic rate (RMR) and that the maintenance and activity costs of the oviduct are responsible for 18% of the variation in elevated laying RMR. Therefore, other energy-consuming physiological mechanisms must be responsible for the remaining unexplained variation in elevated laying RMR. Yolk precursor [vitellogenin (VTG) and very-low-density lipoprotein (VLDL)] production is likely to be costly because it signifies a marked increase in the biosynthetic activity of the liver. We documented the pattern of yolk precursor production in response to daily injections of 17beta-estradiol (E2) in zebra finches (Taeniopygia guttata). Based on this pattern we carried out an experiment in order to evaluate the metabolic costs of producing VTG and VLDL. Our E2 treatment resulted in a significant increase in plasma VTG and VLDL levels within the natural breeding range for the species. Although RMR was measured during the period of active hepatic yolk precursor production, it did not differ significantly within individuals in response to the treatment or when comparing E2-treated birds with sham-injected birds. This could mean that yolk precursor production represents low energy investment. However, we discuss these results in light of possible adjustments between organs that could result in energy compensation.

Body composition in vertebrates is known to show phenotypic plasticity, and changes in organ masses are usually rapid and reversible. One of the most rapid and reversible changes is the transformation of the female avian reproductive organs before breeding. This provides an excellent system to investigate the effects of plasticity in organ size on basal metabolic rate (BMR) through relationships between organ masses and BMR. We compared body composition of female European starlings (Sturnus vulgaris) during various reproductive stages over 3 yr and investigated the pattern of changes in reproductive and nonreproductive organ mass during follicular development and ovulation. Furthermore, we analyzed the relationship between organ mass and resting metabolic rate (RMR) in nonbreeding, laying, and chick-rearing females. Our analysis revealed marked variation in organ masses between breeding stages but no consistent pattern among years except for kidney and pectoralis muscle. Furthermore, changes in nonreproductive organs did not parallel the cycle of growth and regression of the reproductive organs. The oviduct gained 62% of its 22-fold increase in mass in only 3 d, and oviduct regression was just as rapid and began even before the final egg of the clutch was laid, with 42% of the oviduct mass lost before laying of the final egg. In laying females, 18% of variation in mass-corrected RMR was explained by the mass of the oviduct (r2=0.18, n=80, P<0.0005), while pectoralis muscle mass in nonbreeding individuals and liver and gizzard mass in chick-rearing females were the only organs significantly related to RMR (r2=0.31-0.44). We suggest that the nonreproductive organs are affected more by changes in local ecological conditions than the reproductive state itself and that the activity and maintenance cost of the oviduct is high enough that selection has led to a very tight size-function relationship for this organ.

Patients suffering from dementia are at risk of developing some behavior problems during the evolution of the disease. Therefore, it seems important to rule out, from the outset, all physical, psychiatric, metabolic or pharmacological causes in every cognitively impaired patient with disruptive behavior. Before using any medication to treat the patient, it is advisable to attempt a non pharmacological approach. This article offers some advice to the benefit of the caregivers faced with their close ones' behavioral problems. In spite of the best non pharmacological approach, medication can be necessary in order to control and monitor the disruptive behavior. It is imperative to have a thorough knowledge of the psychotropic medications, their impact and possible side effects.

The demented patient's caregivers often feel powerless when confronted with the loss of autonomy and seek advice. The family physician's implication is an important asset to help solve the difficulties associated with the evolution of the disease. This article addresses the most frequent problems encountered and suggests ways to adapt the patient's environment to compensate for cognitive deficits and to improve safety.

The energy cost of egg production in passerine birds has typically been estimated to be 45%-60% of basal metabolic rate (BMR), but this is based on theoretical models using data on energy content of eggs and reproductive tissue; there are still very few empirical data on egg production costs. In this study, we directly measured resting metabolic rate (RMR) in egg-laying female European starlings (Sturnus vulgaris) over 3 yr. We compared these data with RMR of nonbreeding and chick-rearing birds and with estimated energy expenditure generated from a typical energy content model by using empirically derived data from body composition analysis for this species. We found marked variation in RMR between years and between reproductive stages, which complicates comparisons among breeding stages for the assessment of relative egg production costs. On the basis of this method, RMR during egg laying varied from +74% to -13% of nonbreeding RMR and from +20% to -7% of chick-rearing RMR. We therefore used an alternate approach: measuring changes in RMR through the complete cycle of follicle development and ovulation. The increase in RMR from the beginning of prelaying to the six-follicle stage (before first ovulation) when birds have a complete developing follicle hierarchy was 22.4%. This value is still much lower than that estimated from our energy content model. We discuss conceptual problems associated with the theoretical energy content approach but also suggest, on the basis of earlier work done in our lab, that the measured increase in RMR might still underestimate the actual cost of egg production if birds reallocate energy between different physiological systems.

We investigated the quantitative matching of plasma yolk precursor supply (the plasma pool) to follicle demand during yolk formation in European starlings (Sturnus vulgaris). Plasma concentrations of the two yolk precursors, vitellogenin (VTG) and very low density lipoprotein (VLDL), were only elevated coincident with rapid yolk development (RYD) and matched variation in total yolky follicle mass. VTG and VLDL were low (<0.4 microg/mL and <4.2 mg/mL, respectively) in nonbreeders and prebreeders with no yolky follicles, and at clutch completion. They increased to 4.02 microg/mL and 19.4 mg/mL in birds with a full follicle hierarchy (F1-F4), and concentrations then remained high and actually increased up to the point where only a single, yolky (F1) follicle remained. However, there was some evidence for mismatching of supply and demand: (a) precursor concentrations increased throughout the laying cycle even though the number of developing follicles decreased. We suggest that this is because of a requirement to maintain a large precursor pool to maintain high uptake rates; and (b) in birds with a full follicle hierarchy, precursor concentrations were negatively correlated with total follicle mass. This suggests that high uptake rates in large follicles can actually deplete circulating precursor concentrations. Plasma concentrations of both yolk precursors increased rapidly in the early morning with (predicted) time after ovulation, consistent with a lack of fine control of precursor concentrations. However, mean plasma VTG concentrations did not differ between morning or evening samples. In contrast, plasma VLDL concentrations were lower in the morning (16.8 mg/mL) than in the evening (22.9 mg/mL). Although there is marked individual variation in plasma VTG and VLDL (four- to eightfold), both precursors were repeatable in the short term (24 h), and plasma VTG was repeatable over a 14-d interval between successive breeding attempts.

Studies of wintering birds have demonstrated a correlation between social rank and energy expenditures. It is assumed that dominance is energetically costly because of increased activity, possibly caused by elevated androgen levels. As winter acclimatization leads to an increase in metabolic rate, maintaining dominance status in a cold climate can be a substantial challenge. We measured resting metabolic rates in dominant and subordinate dark-eyed juncos (Junco hyemalis) living in small groups in a controlled winter environment. We found no significant effect of social rank when controlling for body size. It has been shown previously that high testosterone levels during the nonbreeding season can lead to higher body conductance, fat loss, and higher nocturnal body temperature. A hypothesis explaining our result is that for juncos it is preferable to maintain low androgen levels during winter and to maintain social rank using a mechanism other than higher agonistic activity.