Metabolic Cost Of Flight Research Articles

It pays to follow the leader: Metabolic cost of flight is lower for trailing birds in small groups

Many bird species commonly aggregate in flocks for reasons ranging from predator defense to navigation. Available evidence suggests that certain types of flocks-the V and echelon formations of large birds-may provide a benefit that reduces the aerodynamic cost of flight, whereas cluster flocks typical of smaller birds may increase flight costs. However, metabolic flight costs have not been directly measured in any of these group flight contexts [Zhang and Lauder, J. Exp. Biol. 226, jeb245617 (2023)]. Here, we measured the energetic benefits of flight in small groups of two or three birds and the requirements for realizing those benefits, using metabolic energy expenditure and flight position measurements from European Starlings flying in a wind tunnel. The starlings continuously varied their relative position during flights but adopted a V formation motif on average, with a modal spanwise and streamwise spacing of [0.81, 0.91] wingspans. As measured via CO2 production, flight costs for follower birds were significantly reduced compared to their individual solo flight benchmarks. However, followers with more positional variability with respect to leaders did less well, even increasing their costs above solo flight. Thus, we directly demonstrate energetic costs and benefits for group flight followers in an experimental context amenable to further investigation of the underlying aerodynamics, wake interactions, and bird characteristics that produce these metabolic effects.

Intraspecific scaling and early life history determine the cost of free-flight in a large beetle (Batocera rufomaculata).

The scaling of the energetic cost of locomotion with body mass is well documented at the interspecific level. However, methodological restrictions limit our understanding of the scaling of flight metabolic rate (MR) in free-flying insects. This is particularly true at the intraspecific level, where variation in body mass and flight energetics may have direct consequences for the fitness of an individual. We applied a 13C stable isotope method to investigate the scaling of MR with body mass during free-flight in the beetle Batocera rufomaculata. This species exhibits large intraspecific variation in adult body mass as a consequence of the environmental conditions during larval growth. We show that the flight-MR scales with body mass to the power of 0.57, with smaller conspecifics possessing up to 2.3 fold higher mass-specific flight MR than larger ones. Whereas the scaling exponent of free-flight MR was found to be like that determined for tethered-flight, the energy expenditure during free-flight was more than 2.7 fold higher than for tethered-flight. The metabolic cost of flight should therefore be studied under free-flight conditions, a requirement now enabled by the 13C technique described herein for insect flight.

Metabolic cost of flight and aerobic efficiency in the rose chafer, Protaetia cuprea (Cetoniinae).

Rose chafer beetles (Protetia cuprea) are pollinators as well as agricultural pests, flying between flowers and trees while foraging for pollen and fruits. Calculating the energy they expend on flying during foraging activity faces the challenge of measuring the metabolic rate (MR) of free-flying insects in an open space. We overcame this challenge by using the bolus injection of 13 C Na-bicarbonate technique to measure their metabolic energy expenditure while flying in a large flight arena. Concurrently, we tracked the insects with high-speed cameras to extract their flight trajectory, from which we calculated the mechanical power invested in flying for each flight bout. We found that the chemical (metabolic) energy input converted to mechanical flight energy output at a mean efficiency of 10.4%±5.2%, with a trend of increased efficiency in larger conspecifics (efficiency scaled with body mass to the power of 1.4). The transition in the summer from a diet of pollen to that of fruits may affect the energy budget available for foraging. Starved P. cuprea, feeding on apples ad libitum, increased their body mass by an average of 6% in 2h. According to our calculations, such a meal can power a 630-m flight (assuming a carbohydrate assimilation efficiency of 90%). Pollen, with a low water and carbohydrate content but rich in proteins and lipids, has a higher caloric content and should assimilate differently when converting food to flight fuel. The high cost of aerial locomotion is inherent to the foraging behavior of rose chafers, explaining their short flight bouts followed by prolonged feeding activity.

Feeding on the wing: energy allocation and prioritization in the hawk moth Manduca sexta (1100.3)

Independently, feeding and exercise have been documented as energetically costly activities. However, how simultaneous exercise and digestion affect energy allocation and exercise performance remains unclear. Using a simple model, we make predictions of how energy may be prioritized during exercise after consumption of food varying in quality. We used Manduca sexta (Sphingidae) to understand how organisms, adapted to “feeding on the wing”, prioritize and resolve a seeming conflict from these two simultaneous competing demands (digestion and activity). Previously, we showed that there was an additive effect of digestion to the metabolic cost of forward flight in M. sexta. In this study we focus on hovering flight to eliminate the effect of flight speed on metabolic rate. Adult, male M. sexta were fed one of 5 treatments (water, 5, 15, 25, 35% sucrose) and then required to sustain hovering flight until exhaustion. We recorded time to exhaustion as a measure of flight performance. Metabolic cost of flight was measured using flow through respirometry.

Hovering and Forward Flight Energetics in Anna's and Allen's Hummingbirds

Aerodynamic theory predicts that the mechanical costs of flight are lowest at intermediate flight speeds; metabolic costs of flight should trend similarly if muscle efficiency is constant. We measured metabolic rates for nine Anna's hummingbirds (Calypte anna) and two male Allen's hummingbirds (Selasphorus sasin) feeding during flight from a free-standing mask over a range of airspeeds. Ten of 11 birds exhibited higher metabolic costs during hovering than during flight at intermediate airspeeds, whereas one individual exhibited comparable costs at hovering and during forward flight up to speeds of approximately 7 m s(-1). Flight costs of all hummingbirds increased at higher airspeeds. Relative to Anna's hummingbirds, Allen's hummingbirds exhibited deeper minima in the power curve, possibly due to higher wing loadings and greater associated costs of induced drag. Although feeding at a mask in an airstream may reduce body drag and, thus, the contributions of parasite power to overall metabolic expenditure, these results suggest that hummingbird power curves are characterized by energetic minima at intermediate speeds relative to hovering costs.

Have wing morphology or flight kinematics evolved for extreme high altitude migration in the bar-headed goose?

Bar-headed geese ( Anser indicus) migrate over the Himalayan mountains, at altitudes up to 9000 m above sea level, where air density and oxygen availability are extremely low. This study determined whether alterations in wing morphology or wingbeat frequency during free flight have evolved in this species to facilitate extreme high altitude migration, by comparing it to several closely related goose species. Wingspan and wing loading scaled near isometrically with body mass across all species (with power scaling exponents of 0.22 and 0.47, respectively), and wingbeat frequency scaled negatively to mass (scaling exponent of − 0.167). Bar-headed geese had the largest wingspan residual and smallest wing loading residual from these allometric relationships, suggesting that they are at the top end of the wing size distribution. These morphological characters of bar-headed geese were not outside the normal variation exhibited by low altitude species, however, being within the prediction intervals of the regression. This was particularly true after the data were corrected for phylogeny using the independent contrasts method. Wingbeat frequencies of bar-headed geese during steady flight were the same as low altitude geese, both with and without correcting for phylogeny. Without adjusting other kinematic features (e.g., wing motion and generated wake structure) to supplement lift generation in low air densities, the metabolic costs of flight in bar-headed geese at high altitude could exceed the already high costs at sea level. The apparent lack of morphological and kinematic adaptation emphasizes the importance of physiological adaptations for enhancing oxygen transport and utilization in this species.

Metabolic costs of avian flight in relation to flight velocity: a study in Rose Coloured Starlings (Sturnus roseus, Linnaeus)

The metabolic costs of flight at a natural range of speeds were investigated in Rose Coloured Starlings (Sturnus roseus, Linnaeus) using doubly labelled water. Eight birds flew repeatedly and unrestrained for bouts of 6 h at speeds from 9 to 14 m s(-1) in a low-turbulence wind tunnel, corresponding to travel distances between 200 and 300 km, respectively. This represents the widest speed range where we could obtain voluntarily sustained flights. From a subset of these flights, data on the wing beat frequency (WBF) and intermittent flight behaviour were obtained. Over the range of speeds that were tested, flight costs did not change with velocity and were on an average 8.17+/-0.64 W or 114 W kg(-1). Body mass was the only parameter with a significant (positive) effect on flight costs, which can be described as EE(f)=0.741 M(0.554). WBF changed slightly with speed, but correlated better with body mass. Birds showed both types of intermittent flight, undulating and bounding, but their frequencies did not systematically change with flight speed.

Temporary flightlessness as a potential cost of reproduction in pre‐laying Common Eiders Somateria mollissima

The rapid growth and reabsorption of the avian ovary is thought to be adaptive, as it reduces predation risk and the metabolic cost of flight. In this paper, we use an extreme case of parental investment to show how the survival of gravid birds may be impaired by reduced take‐off ability. In still air, temporary flightlessness is regularly observed in female Common Eiders Somateria mollissima preparing for breeding. From a sample of pre‐laying females collected in the Baltic Sea, we quantified the relationships among body reserves, organ mass and take‐off ability using a general model of take‐off performance. Average body mass at the beginning and end of follicular growth was, respectively, 32% and 43% higher than winter body mass. Wing‐loading increased significantly during ovary development whereas the relative mass of flight muscles decreased. In contrast, organ mass and somatic body mass were constant from early follicular growth until laying, indicating that the observed increase in body mass was caused by ovary growth. The average specific lift production of individuals collected at the beginning of follicular growth was 9.7 N/kg, which is similar to the lift required to become airborne (9.8 N/kg). As ovary mass increased, lift production decreased to 9.2 N/kg at the onset of laying. These results indicate that temporary flightlessness results from the accumulation of large body reserves and subsequent ovarian growth. Predators of Common Eiders are diverse and may come from air, water and land. We suggest that temporary flightlessness may decrease adult survival through predation, and may represent an important cost of reproduction.

The metabolic cost of flight in unrestrained birds.

Oxygen consumption and carbon dioxide production were measured during flight in unrestrained starlings by a new method. Mean RQ after the first 30 min of flight was 0.69 +/- 0.08 (+/- S.D.). Mean rate of carbon dioxide production was 19.7 +/- 2.2 ml CO2/min, which corresponds to a metabolic rate of 8.9 +/- 1 W. Metabolic rate during flight did not change significantly over a range of air speeds from 8 to 18 m/s and birds would not fly at speeds outside of this range. Current theories of bird flight predict a large change in metabolic rate over the same range of speeds. Wingbeat frequency was constant at 12 +/- 0.5 Hz. Wingbeat amplitude reached a minimum at a speed of 14 m/s and increased at both higher and lower speeds. Angle between the body and horizontal was least at high speeds and increased at low speeds. As existing theories do not take into account the change of drag resulting from changes in body attitude, this may be a cause of the discrepancies between theory and observation.

Activity patterns and energetics of the moth, Hyalophora cecropia.

ABSTRACT The time of activity and the duration of active periods (flight) of moths of the species Hyalophora cecropia has been determined by monitoring thoracic temperature. The metabolic cost of flight per day and per adult life has been determined directly by measuring O2 consumption and indirectly by analysis of cooling curves of individual moths. An energy balance sheet has been derived which gives the metabolic cost of flight and maintenance (during torpor) over the insect’ s adult life. The metabolic stores mobilized for daily activity appear to be fixed and independent of air temperature. This mobilization of fat stores may be under hormonal control. It is metabolically more expensive for moths to be active at low air temperatures. The number and duration of active periods at low air temperatures is reduced, but, the metabolic expenditure for activity is equal to that of animals held at higher air temperatures. Females have a smaller total energy reserve than males. The number of active periods per day is not significantly different between the sexes at any given temperature, but in females the active periods are significantly shorter in duration. The flight speed has been determined, and estimates of the flight range per day and per adult life have been calculated. The ecology of H. cecropia has been discussed with respect to the timing and duration of active periods, the range and speed of flight, and the energetic cost of flight and maintenance metabolism.