Metabolic cost of incubation in the Laysan albatross and Bonin petrel

AnimalTraits - a curated animal trait database for body mass, metabolic rate and brain size

Trait databases have become important resources for large-scale comparative studies in ecology and evolution. Here we introduce the AnimalTraits database, a curated database of body mass, metabolic rate and brain size, in standardised units, for terrestrial animals. The database has broad taxonomic breadth, including tetrapods, arthropods, molluscs and annelids from almost 2000 species and 1000 genera. All data recorded in the database are sourced from their original empirical publication, and the original metrics and measurements are included with each record. This allows for subsequent data transformations as required. We have included rich metadata to allow users to filter the dataset. The additional R scripts we provide will assist researchers with aggregating standardised observations into species-level trait values. Our goals are to provide this resource without restrictions, to keep the AnimalTraits database current, and to grow the number of relevant traits in the future.

Measurement(s)	metabolic rate quantification • body mass • brain size
Technology Type(s)	metabolic rate measurement • body mass quantification • brain mass brain volume

The roles of diffusion and convection in ventilation of animal burrows

The relationship between body mass and the respiratory microenvironment of burrowing animals is examined using artificial burrows containing surrogate animals that simulate O₂ consumption by removal of air and simultaneous replacement with N₂. Allometric relationships between body mass and burrow radius, nest chamber radius, and O₂ consumption rate show that published mathematical predictions of diffusion-mediated gas exchange are adequate to describe the respiratory environments of animals in small blind-ending burrows through porous substrata. Diffusion is sufficient to ventilate burrows containing small mammals weighing less than 340 g, or subterranean nest chambers connected to the surface by one or more tunnels containing mammals weighing less than 30 kg. Outside of these limits, convection prevails and prevents the development of hypoxic conditions, particularly in burrows of mammals weighing more than 1300 g.

Reassessing the definition of basal metabolic rate: Circadian considerations in avian studies

The importance of daily fluctuations in avian basal metabolic rate (BMR) was introduced in the classic paper by Aschoff and Pohl (1970) characterizing circadian differences. Since that time, there has been a shift in the BMR literature to accept only values measured in the ρ- (resting) phase of the day as true BMR. We argue that α- (active) and ρ-phases both represent BMR, analogous to the plasticity of BMR seen in seasonal variations, or associated with changes in body composition and restrictions in diet. Furthermore, we demonstrate that circadian differences in BMR are not even present in most polar birds and are sometimes absent in a variety of non-passerines. We argue for the ecological value of a 24 h BMR in order to compare with daily energy expenditure (field metabolic rate, FMR), which integrates entire days. We make recommendations for the reporting of BMR with sufficient information so readers will know time, season, etc. We also suggest that measures of BMR can be accepted during reproduction in birds, though with some caution.

Ingested plastic as a route for trace metals in Laysan Albatross (Phoebastria immutabilis) and Bonin Petrel (Pterodroma hypoleuca) from Midway Atoll

Seabirds are declining faster than any other group of birds, with plastic ingestion and associated contaminants linked to negative impacts on marine wildlife, including >170 seabird species. To provide quantitative data on the effects of plastic pollution, we sampled feathers and stomach contents from Laysan Albatross (Phoebastria immutabilis) and Bonin Petrel (Pterodroma hypoleuca) on Midway Atoll, North Pacific Ocean, and assessed our ability to detect change over time by synthesizing previous studies. Between 25 and 100% of fledglings exceed international targets for plastic ingestion by seabirds. High levels of ingested plastic were correlated with increased concentrations of chlorine, iron, lead, manganese, and rubidium in feathers. The frequency of plastic ingestion by Laysan Albatross and concentration of some elements in both species is increasing, suggesting deterioration in the health of the marine environment. Variability in the frequency of plastic ingestion by Laysan Albatross may limit their utility as an indicator species.

The use of body mass loss to estimate metabolic rate in birds

During starvation, energy production occurs at the expense of body reserve utilisation which results in body mass loss. Knowing the role of the fuels involved in this body mass loss, along with their energy density, can allow an energy equivalent of mass loss to be calculated. Therefore, it is possible to determine daily energy expenditure (DEE) if two body mass loss measurements at an interval of a few days are obtained. The technique can be cheap, minimally stressful for the animals involved, and the data relatively simple to gather. Here we review the use of body mass loss to estimate DEE in birds through critiquing the strengths and weaknesses of the technique, and detail the methodology and considerations that must be adhered to for accurate measures of DEE to be obtained. Owing to the biology of the species, the use of the technique has been used predominantly in Antarctic seabirds, particularly penguins and albatrosses. We demonstrate how reliable the technique can be in predicting DEE in a non-Antarctic species, common eiders (Somateria mollissima), the female of which undergoes a fasting period during incubation. We conclude that using daily body mass loss to estimate DEE can be a useful and effective approach provided that (1) the substrate being consumed during mass loss is known, (2) the kinetics of body mass loss are understood for the species in question and (3) only species that enter a full phase II of a fast (where substrate catabolism reaches a steady state) and are not feeding for a period of time are appropriate for this method.

The Allometry of Avian Basal Metabolic Rate: Good Predictions Need Good Data

Basal metabolic rate (BMR) is often predicted by allometric interpolation, but such predictions are critically dependent on the quality of the data used to derive allometric equations relating BMR to body mass (Mb). An examination of the metabolic rates used to produce conventional and phylogenetically independent allometries for avian BMR in a recent analysis revealed that only 67 of 248 data unambiguously met the criteria for BMR and had sample sizes with n>/=3. The metabolic rates that represented BMR were significantly lower than those that did not meet the criteria for BMR or were measured under unspecified conditions. Moreover, our conventional allometric estimates of BMR (W; logBMR=-1.461+0.669logMb) using a more constrained data set that met the conditions that define BMR and had n>/=3 were 10%-12% lower than those obtained in the earlier analysis. The inclusion of data that do not represent BMR results in the overestimation of predicted BMR and can potentially lead to incorrect conclusions concerning metabolic adaptation. Our analyses using a data set that included only BMR with n>/=3 were consistent with the conclusion that BMR does not differ between passerine and nonpasserine birds after taking phylogeny into account. With an increased focus on data mining and synthetic analyses, our study suggests that a thorough knowledge of how data sets are generated and the underlying constraints on their interpretation is a necessary prerequisite for such exercises.

Variation in energy expenditure among black-legged kittiwakes: effects of activity-specific metabolic rates and activity budgets

We sought to determine the effect of variation in time-activity budgets (TABs) and foraging behavior on energy expenditure rates of parent black-legged kittiwakes (Rissa tridactyla). We quantified TABs using direct observations of radio-tagged adults and simultaneously measured field metabolic rates (FMR) of these same individuals (n=20) using the doubly labeled water technique. Estimated metabolic rates of kittiwakes attending their brood at the nest or loafing near the colony were similar (ca. 1.3 x basal metabolic rate [BMR]), although loafing during foraging trips was more costly (2.9 x BMR). Metabolic rates during commuting flight (7.3 x BMR) and prey-searching flight (6.2 x BMR) were similar, while metabolic rates during plunge diving were much higher (ca. 47 x BMR). The proportion of the measurement interval spent foraging had a positive effect on FMR (R2=0.68), while the combined proportion of time engaged in nest attendance and loafing near the colony had a negative effect on FMR (R2=0.72). Thus, more than two-thirds of the variation in kittiwake FMR could be explained by the allocation of time among various activities. The high energetic cost of plunge diving relative to straight flight and searching flight suggests that kittiwakes can optimize their foraging strategy under conditions of low food availability by commuting long distances to feed in areas where gross foraging efficiency is high.

Comparison of methods for evaluating energy expenditure of incubating wandering albatrosses

Measurements of incubation energetics can vary depending on the method used to measure metabolism of an incubating bird. Therefore, we evaluated the energy expenditure of six male and four female wandering albatrosses (Diomedea exulans Linnaeus) using doubly labeled water (DLW), the rate of mass loss, and estimates of metabolic water production derived from water influx rate (WIR). Incubation metabolic rates (IMR) determined with DLW (169+/-21 kJ x kg(-1) x d(-1) SD) were significantly lower than estimates derived from mass loss (277+/-46 kJ x kg(-1) x d(-1) SD) and WIR (males=289+/-60 kJ x kg(-1) x d(-1) vs. females=400+/-69 kJ x kg(-1) x d(-1) SD). Estimates of IMR from mass loss and WIR were similar to IMR (305+/-39 kJ x kg(-1) x d(-1) SD) determined by respirometry in a previous study, and IMR from DLW was similar to estimates based on heart rate (HR; 147+/-26 kJ x kg(-1) x d(-1) SD) determined in another study. Applying the different measurements of IMR to construct an energy budget, we estimate that a breeding pair of wandering albatrosses spends 124-234 MJ to incubate the egg for 78 d. Finally, IMRs determined with DLW and HR were similar to estimated basal metabolic rates derived from six different allometric equations, suggesting that heat production from adult maintenance metabolism is sufficient to incubate the egg.

The use of body mass loss to estimate metabolic rate in fasting sea birds: a critical examination based on emperor penguins (Aptenodytes forsteri)

1. The validity of the body mass loss (BML) method to estimate incubation and molting metabolic rate (MR) in sea birds is examined on the basis of data in emperor penguins (Aptenodytes forsteri). 2. The BML composition of emperors during mid incubation is revised (61.7% fat, 5.9% protein and 32.4% water; energy equivalent of BML = 25.5 kJ/g). 3. Using these data in short-term fasting petrels and penguins, or with BML obtained at the beginning or at the end of the fast in long-term fasting species, may lead to up to 2-fold overestimates of incubation metabolic rate (IMR). Similarly, molting MR may be overestimated by up to three times. 4. The use of the 25.5 kJ/g energy equivalent with BML obtained during middle part of the incubation shift seems valid in long-term fasting species. It is suggested that IMR within the thermoneutral zone might be close to basal MR in most antarctic and sub-antarctic sea birds.

Ratios of hatchling and adult mass-independent metabolism: a physiological index to the altricial-precocial continuum

Measures of metabolism which are theoretically mass-independent (MIM values = BMR divided by M0.67) are calculated for non-passerine species from data in the existing literature. These MIM values are, in fact as the acronym implies, essentially mass independent, with only 8.2% of the variation in MIM values attributable to log mass. In 10 of the 12 orders for which data were analysed, the slopes of the regressions of MIM values on log body mass do not differ significantly from zero. A dimensionless index of the intensity of the energy metabolism of hatchlings relative to that of conspecific adults is derived based upon the mass-independent measures of metabolism for adults and hatchlings. This ranking of metabolic maturity at hatching, a physiological index, is compared with the most commonly used classification of the avian altricial-precocial continuum which is based upon morphological and behavioral characteristics. Several taxonomic groups appear more precocial metabolically than indicated by their ranking based upon morphological and behavioral criteria.

Accuracy of the Haldane method as an indirect measure of metabolism

Metabolic rates of barn owls increased as ambient temperature decreased below the thermoneutral zone. The Haldane method was as reliable as an O2 analyzer in measuring the metabolic rates of captive barn owls. However, at lowered ambient temperature (below 5 degrees C) there was a slight disparity in the metabolic rates determined by the two methods. The Haldane method has the potential of being used in a field situation (i.e. it is reliable, portable and relatively inexpensive).