Energy expenditures for flight,aerodynamic quality,and colonization of forest habitats by birds

The power that the birds can use for flight (available power) and the power required for flight according to physical laws (requisite power) grow with an increase in body mass, the exponents of the corresponding functions being different. Small birds can follow different strategies, either improving the aerodynamic quality of the body (thereby saving the excess available power) or sacrifice aerodynamic quality in favor of morphological adaptation to factors other than the demands of flight proper, which provides the possibility of utilizing a wider range of ecological niches. A hypothesis is proposed that the high metabolic rate of passerine birds, compared to representatives of other bird orders, is an adaptation to maneuverable (i.e., relatively low-speed) flight necessary for successful colonization of forest habitats. The speed that birds of such size can develop according to the scaling theory is too high for nesting and foraging in tree crowns, and its reduction is possible in two ways: by increasing air drag or by changing the style of flight (by analogy with airplane vs. helicopter). The first way is feasible, but a high air drag due to morphological modifications (e.g., in the size of the tail or characteristics of the wing) interferes with the possibility of long-distance migration flight, as energy expenditures for it will exceed the energy potential of the bird. This is why migratory nonpasserine birds, which have used this strategy, are practically absent in forests of the temperate zone. Therefore, more promising is the second way involving transition to a new flight style and, in a certain sense, to a new morphophysiological organization. Passerines have achieved this by changing their flight style so that the wing actively generates forces (lift and thrust) only in downstroke. Such a flight requires more energy, and, to provide it in sufficient amounts, passerine birds have increased their basal metabolic rate (BMR). Thus, both their flight energy expenditures and BMR are higher than in nonpasserines. Remarkably, among approximately 8660 extant bird species known today, more than half (about 5100 species) belong to the order Passeriformes. Such a ratio, unknown in any other vertebrate class, is evidence that passerines have gained a considerable biological advantage over all other birds due to their increased BMR.     

Flight speed of seabirds in relation to wind speed and direction

We studied flight speed among all major seabird taxa. Our objectives were to provide further insight into dynamics of seabird flight and to develop allometric equations relating ground speed to wind speed and direction for use in adjusting seabird density estimates (calculated from surveys at sea) for the effect of bird movement. We used triangulation at sea to estimate ground speeds of 1562 individuals of 98 species. Species sorted into 25 “groups” based on similarity in ground speeds and taxonomy. After they were controlled for differences inground speed, the 25 groups sorted into eight major “types” on the basis of response to wind speed and wind direction. Wind speed and direction explained 1664% of the variation in ground speed among seabird types. For analyses on air speed (ground speed minus apparent wind speed), we divided the 25 groups according to four flight styles: gliding, flap-gliding, glide-flapping and flapping. Tailwind speed had little effect on air speed of gliders (albatrosses and large gadfly petrels), but species that more often used flapping decreased air speed with increase in tailwinds. All species increased air speeds significantly with increased headwinds. Gliders showed the greatest increase relative to increase in headwind speed and flappers the least. With tailwind flight, air speeds were greatest among species with highest wing loading for each flight style except gliders, which showed no relationship. For headwind flight, species with higher wing loading had higher air speeds; however, the relation was weaker in flappers compared with species using some amount of gliding. In contrast, analyses for air speed ratio (i.e. difference between air speed in acrosswinds [with no apparent wind] and speed flown into headwinds, or with tailwinds, divided by speed acrosswind) revealed that among species using some flapping, and with lower wing loading (surface-feeding shearwaters, small gadfly petrels, storm petrels, phalaropes, gulls and terns), adjusted air speeds more than those with higher wing loading (alcids, “diving shearwaters”, “Manx-type shearwaters”, pelicans, boobies and cormorants). As a result, most flappers of low wing loading flew much faster than V_mr (the most energy efficient air speed per distance flown) when flying into headwinds. We suggest that better-than-predicted gliding performance with acrosswinds and tailwinds of large gadfly petrels, compared with albatrosses, resulted from a different type of “soaring” not previously described in seabirds.     

温度和湿度对麦长管蚜飞行能力的影响

利用计算机控制的微小昆虫飞行磨系统测定了温度、湿度对麦长管蚜Sitobion avenae飞行能力的影响。结果表明,适于飞行的温度为12～22℃,湿度为60%～80%。在温度8℃以下或25℃以上,其飞行能力明显降低。在温度18℃时,麦长管蚜的平均飞行时间、飞行距离最大分别为3.101 h、3.676 km。在相对湿度40%、60%和80%时,飞行时间分别为1.573 h、2.272 h和3.032 h,飞行距离与湿度的关系与飞行时间相似。飞行速度随温度的增高而加快,在相对湿度60%左右时,麦长管蚜的平均飞行速度较快。在20℃,相对湿度80%条件下,单个个体的最大飞行时间、最大飞行距离和最大飞行速度可达14.32 h、22.51 km和1.57 km/ h,表现出麦长管蚜具有较强的飞行能力。     

Flight energetics and dispersal capability of the fire ant, Solenopsis invicta Buren

Experiments were conducted to estimate the flight capabilities of fire ant (Solenopsis invicta Buren) alates. These experiments were designed to: (1) quantify energetic expenditure during fixed flight; (2) characterize metabolic substrates of male and female alates; (3) estimate flight speed of male and female alates; and (4) quantify wingbeat frequency and water loss of females during flight. Flying males (in closed-system respirometry) increased metabolic rate approximately 38.4-fold over resting rate. Females increased metabolic rate approximately 51-fold (closed-system respirometry) and 48-fold (flow-through respirometry) over resting rate. Female alates had a mean respiratory quotient (RQ) of 0.999, indicating reliance on carbohydrates. The mean RQ of males was significantly lower (0.867). The flight speed of females on a circular flight mill averaged approximately 0.7 m s(-1), and increased with temperature but decreased with increasing body mass. The flight speed of males was 43% greater (approximately 1.0 m s(-1)) and increased linearly with temperature and increasing body mass. Female alates lost an average of 1.8 mg water h(-1) during flight. A simple energetics model, combined with previous work on the nutrient content of S. invicta and patterns of CO(2) release observed in this study, indicate that the flight capability of S. invicta female alates is limited to <5 km in the absence of wind.     

To what extent can the tiny parasitoid wasps,Eretmocerus mundus,fly upwind?

Body miniaturization in insects is predicted to result in decreased flight speed and therefore limited ability of these insects to fly upwind. Therefore, tiny insects are often regarded as relying on passive dispersal by winds. We tested this assumption in a wind tunnel by measuring the burst speed of Eretmocerus mundus (Mercet), a beneficial parasitoid wasp with body length <1 mm. Insects were filmed flying upwind towards a UV light source in a range of wind speed 0–0.5 m/s. The Insects flew towards the UV light in the absence and presence of wind but increased their flight speed in the presence of wind. They also changed flight direction to be directly upwind and maintained this body orientation even while drifted backwards relative to the ground by stronger winds. Field measurements showed that the average flight speed observed in the wind tunnel (0.3 m/s) is sufficient to allow flying between plants even when the wind speed above the vegetation was 3–5 folds higher. A simulation of the ability of the insects to control their flight trajectory towards a visual target (sticky traps) in winds show that the insects can manipulate their progress relative to the ground even when the wind speed exceeds their flight speed. The main factors determining the ability of the insects to reach the trap were trap diameter and the difference between insect flight speed and wind speed. The simulation also predicts the direction of arrival to the sticky target showing that many of the insects reach the target from the leeward side (i.e. by flight upwind). In light of these results, the notion that miniature insects passively disperse by winds is misleading because it disregards the ability of the insects to control their drift relative to the ground in winds that are faster than their flight speed.     

The flight of pipistrelle bats Pipistrellus pipistrellus during pregnancy and lactation

A group of 20 pipistrelle bats were taken into captivity and allowed free flight and association within a flight room where they gave birth to and successfully reared 17 young. The flight of the females was recorded during pregnancy, early lactation and post-lactation by using stroboscopic stereophotogrammetry (153 flights reconstructed in total). During the investigation body mass was altering owing to reproductive condition, and changes in mass were recorded daily for all (adult and juvenile) bats during the entire study period, which lasted from two weeks before the last birth until release, when the oldest baby was 43 days old. All bats were individually marked, and detailed morphological measurements were made. Pregnant and post-lactating bats were heavier than lactating bats, which showed the lowest wingbeat frequencies. The flight speeds of pregnant, lactating and post-lactating bats showed no significant differences, and this may be because the pregnant bats appeared to have a wider scope for selecting flight speed than the other two reproductive groups, or than animals studied previously. The group of bats as a whole decreased flight speed (scaling as M^-043) and increased wingbeat frequency (scaling as M^0.58) as their mass increased. Wingbeat amplitude showed no relation to body mass, wing area or span, flight speed or frequency. A flight performance model applied to the experimental results and optimum flight conditions is used to predict cost of transport and mechanical power for steady flight, and equilibrium wingbeat amplitude which is compared with observations.     

Influence of Some Potential Predation Risk Factors and Interaction between Predation Risk and Cost of Fleeing on Escape by the Lizard Sceloporus virgatus

Escape theory predicts that flight initiation distance (predator–prey distance when escape begins) increases as predation risk increases and decreases as cost of fleeing increases. Scant information is available about the effects of some putative predation risk factors and about interaction between simultaneously operating risk and cost of fleeing factors on flight initiation distance and distance fled. By simulating an approaching predator, I studied the effects of body temperature (BT), distance to nearest refuge, and eye contact with a predator, as well as simultaneous effects of predator approach speed and female presence/absence on escape behavior by a small ectothermic vertebrate, the lizard Sceloporus virgatus. Flight initiation distance decreased as BT increased, presumably because running speed increases as BT increases, facilitating escape. Distance to nearest refuge was unrelated to BT or flight initiation distance. Substrate temperature was only marginally related, and air temperature was not related to flight initiation distance. Eye contact did not affect flight initiation during indirect approaches that bypassed lizards by a minimum of 1 m, but an effect of eye contact found in other studies during direct approach might occur. Predator approach speed and presence of a female interactively affected flight initiation distance, which increased as speed increased and decreased when a female was present. In the presence of a female, flight initiation distance was far shorter than when no female was present. The high cost of forgoing a mating opportunity accounts for the interaction because the difference between female presence and absence is greater when risk is greater.     

A statistical framework for genetic association studies of power curves in bird flight

How the power required for bird flight varies as a function of forward speed can be used to predict the flight style and behavioral strategy of a bird for feeding and migration. A U-shaped curve was observed between the power and flight velocity in many birds, which is consistent to the theoretical prediction by aerodynamic models. In this article, we present a general genetic model for fine mapping of quantitative trait loci (QTL) responsible for power curves in a sample of birds drawn from a natural population. This model is developed within the maximum likelihood context, implemented with the EM algorithm for estimating the population genetic parameters of QTL and the simplex algorithm for estimating the QTL genotype-specific parameters of power curves. Using Monte Carlo simulation derived from empirical observations of power curves in the European starling (Sturnus vulgaris), we demonstrate how the underlying QTL for power curves can be detected from molecular markers and how the QTL detected affect the most appropriate flight speeds used to design an optimal migration strategy. The results from our model can be directly integrated into a conceptual framework for understanding flight origin and evolution.     

Sexual selection on flight endurance,flight-related morphology and physiology in a scrambling damselfly

We have limited knowledge on the mechanistic base of sexual selection, especially in scrambling species. This asks for a functional approach that explores the link between each component of the phenotype-performance-fitness axis and that includes both morphological and physiological traits. We explored the phenotype-performance-fitness axis in the scrambling damselfly Coenagrion puella by studying the links between a set of physiological and morphological traits, flight performance (flight speed and flight endurance), and short-term mating success. As expected for scrambling competition, there was sexual selection for increased flight endurance rather than for increased flight speed. For fat content, we could demonstrate the full phenotype-performance-fitness axis, where selection for a higher fat content could be explained by the sexual selection for a higher flight endurance and the positive covariation between fat content and flight endurance. For three other traits (size, relative flight muscle mass and wing loading), however, we detected selection that could not be explained via their effect on flight performance, generating novel testable hypotheses about how the covariation between these traits and mating success is generated. This also urges caution when using morphological traits as proxies for flight speed and flight endurance in phenotypic selection studies.     

Morphology, Velocity, and Intermittent Flight in Birds

Body size, pectoralis composition, aspect ratio of the wing,and forward speed affect the use of intermittent flight in birds.During intermittent non-flapping phases, birds extend theirwings and glide or flex their wings and bound. The pectoralismuscle is active during glides but not during bounds; activityin other primary flight muscles is variable. Mechanical power,altitude, and velocity vary among wingbeats in flapping phases;associated with this variation are changes in neuromuscularrecruitment, wingbeat frequency, amplitude, and gait. Speciesof intermediate body mass (35–158 g) tend to flap-glideat slower speeds and flap-bound at faster speeds, regardlessof the aspect ratio of their wings. Such behavior may reducemechanical power output relative to continuous flapping. Smallerspecies (<20 g) with wings of low aspect ratio may flap-boundat all speeds, yet existing models do not predict an aerodynamicadvantage for the flight style at slow speeds. The behaviorof these species appears to be due to wing shape rather thanpectoralis physiology. As body size increases among species,percent time spent flapping increases, and birds much largerthan 300 g do not flap-bound. This pattern may be explainedby adverse scaling of mass-specific power or lift per unit poweroutput available from flight muscles. The size limit for theability to bound intermittently may be offset somewhat by thescaling of pectoralis composition. The percentage of time spentflapping during intermittent flight also varies according toflight speed.     

Speed stability in birds

Solutions for the speed stability problem in bird flight at low speed are developed. Speed stability is usually considered not to exist in flapping flight at speeds below the speed of the minimum power required, and in gliding flight below the speed for maximum range. Approaches thus far for solving the speed stability problem are relating to a 1-degree-of-freedom model of the bird where the speed is regarded as the only motion variable involved. However, a speed deviation is inherently associated with a deviation in the height. In this paper, an expanded treatment with an appropriate mathematical model is presented. The expanded treatment is based on a 2-degree-of-freedom model of the bird. Thus, it is possible to account for the speed and the height changes. With this expanded treatment, it can be shown that there is speed stability in the gliding flight of birds, whether the speed is below the speed for maximum range or above. This also holds for flapping flight with regard to speeds below the speed of the minimum power required. Further, it is shown that there can be speed instability if the bird acts as a controller to suppress height deviations. For this purpose, a model of the bird acting as a controller is presented.     

Artificial evolution of the morphology and kinematics in a flapping-wing mini-UAV

Birds demonstrate that flapping-wing flight (FWF) is a versatile flight mode, compatible with hovering, forward flight and gliding to save energy. This extended flight domain would be especially useful on mini-UAVs. However, design is challenging because aerodynamic efficiency is conditioned by complex movements of the wings, and because many interactions exist between morphological (wing area, aspect ratio) and kinematic parameters (flapping frequency, stroke amplitude, wing unfolding). Here we used artificial evolution to optimize these morpho-kinematic features on a simulated 1 kg UAV, equipped with wings articulated at the shoulder and wrist. Flight tests were conducted in a dedicated steady aerodynamics simulator. Parameters generating horizontal flight for minimal mechanical power were retained. Results showed that flight at medium speed (10-12 m s(-1)) can be obtained for reasonable mechanical power (20 W kg(-1)), while flight at higher speed (16-20 m s(-1)) implied increased power (30-50 W kg(-1)). Flight at low speed (6-8 m s(-1)) necessitated unrealistic power levels (70-500 W kg(-1)), probably because our simulator neglected unsteady aerodynamics. The underlying adaptation of morphology and kinematics to varying flight speed were compared to available biological data on the flight of birds.     

Moult, flight performance and wingbeat kinematics during take-off in European starlings Sturnus vulgaris

The effects of natural moult on avian flight performance have received relatively little attention, yet moult is an important part of the annual cycle. Quantification of flight costs will help to explain the diversity of moult patterns observed in avian taxa. Take‐off from the ground requires a high power output from the flight muscles compared to other modes of flight, and is an important feature of foraging and predation escape. The present study was designed to quantify the effect of natural moult and new plumage on the take‐off strategy, kinematics, and flight performance of European starlings Sturnus vulgaris. A high‐speed (185 Hz) cine camera was used to film seven European starlings on three occasions: session 1, two weeks prior to the onset of moult; session 2, during mid‐moult; and session 3, two weeks after full plumage had re‐grown. From subsequent film analysis, we assessed take‐off speed and angle, the energy gained per wingbeat, and wingtip kinematics. Take‐off strategy (measured by angle and speed) altered through the course of the three experimental sessions, i.e. ascent angle decreased and take‐off speed increased. Energy gained per wingbeat did not vary, suggesting there was no significant decrease in flight performance due to moult, but there was a significant improvement in take‐off performance due to renewal of flight plumage. Wingbeat amplitude increased in association with moult and after flight plumage had been completely renewed. The European starlings incurred relatively minor flight costs due to moult, when comparing before‐moult with during‐moult take‐off performance. The apparent absence of additional flight costs associated with moult may reflect a decreased mechanical performance of year‐old feathers (which are replaced during the moult) and may also help to explain the relatively long duration of the moult in this species. This study also provides evidence of the benefits of plumage renewal, as take‐off performance is improved after moult has been completed.     

金纹细蛾飞行能力测定

【目的】明确金纹细蛾Lithocolletis ringoniella自身生理状态下的飞行能力,了解其飞行生物学的基础参数。【方法】利用昆虫飞行磨系统,室内测定了金纹细蛾雌雄成虫不同日龄和性别以及5日龄雌雄成虫补充营养(5%蜂蜜水)与交配状态下的飞行距离、飞行时间、飞行速度等参数。【结果】连续吊飞12 h的结果显示,金纹细蛾3-6日龄成虫飞行能力较强,5日龄成虫飞行能力最强; 5日龄雌成虫的平均 飞行距离、飞行时间和飞行速度分别为2.293±0.254 km, 5.341±0.617 h和0.711±0.126 km/h, 5日龄雄成虫的平均飞行距离、飞行时间和飞行速度分别为2.142±0.276 km, 5.132±0.628 h和0.620±0.132 km/h, 说明雌雄成虫间飞行能力差异不显著。金纹细蛾5日龄雌雄成虫取食5%蜂蜜水后其飞行能力较对照显著提高,取食5%蜂蜜水后5日龄雌成虫的飞行距离、飞行时间和飞行速度较对照(取食清水)的分别提高46.945%, 15.430%和15.978%;5日龄雄成虫的飞行距离、飞行时间和飞行速度较对照分别提高42.610%, 13.590%和6.529%。交配后5日龄雌成虫的飞行距离、飞行时间和飞行速度较未交配雌成虫的分别提高41.628%, 7.152%和39.925%,而5日龄雄成虫交配后飞行能力则较未交配雄成虫的分别降低35.823%, 17.888%和46.129%。【结论】金纹细蛾成虫具有一定的飞行能力,补充营养和雌雄交配状态对飞行能力有重要影响。     

Flight costs of long,sexually selected tails in hummingbirds

The elongated tails adorning many male birds have traditionally been thought to degrade flight performance by increasing body drag. However, aerodynamic interactions between the body and tail can be substantial in some contexts, and a short tail may actually reduce rather than increase overall drag. To test how tail length affects flight performance, we manipulated the tails of Anna''s hummingbirds (Calypte anna) by increasing their length with the greatly elongated tail streamers of the red-billed streamertail (Trochilus polytmus) and reducing their length by removing first the rectrices and then the entire tail (i.e. all rectrices and tail covert feathers). Flight performance was measured in a wind tunnel by measuring (i) the maximum forward speed at which the birds could fly and (ii) the metabolic cost of flight while flying at airspeeds from 0 to 14 m s⁻¹. We found a significant interaction effect between tail treatment and airspeed: an elongated tail increased the metabolic cost of flight by up to 11 per cent, and this effect was strongest at higher flight speeds. Maximum flight speed was concomitantly reduced by 3.4 per cent. Also, removing the entire tail decreased maximum flight speed by 2 per cent, suggesting beneficial aerodynamic effects for tails of normal length. The effects of elongation are thus subtle and airspeed-specific, suggesting that diversity in avian tail morphology is associated with only modest flight costs.     

美洲斑潜蝇在不同温度下的飞行能力

利用昆虫飞行磨测试了美洲斑潜蝇Liriomyza sativae在18℃到36℃条件下的飞行能力。结果表明：在33℃下美洲斑潜蝇的飞行能力最强,个体最大飞行距离、最高飞行速度和最长飞行时间分别为8.22 km、1.10 km/h和253.50 min,其平均飞行距离为0.95 km。其飞行的适温范围是21～36℃,18℃为其飞行的下限温度。从18～33℃,随着温度的升高平均飞行距离（0.08～0.95 km）和平均飞行时间(6.57～47.94 min)也在增加,但到36℃又开始下降;雌虫比雄虫飞行能力强。在理论上,美洲斑潜蝇能靠自身飞行扩散0.08～0.95 km。     

Quantitative studies on the release of locust adipokinetic hormone

Fractionation of methanolic extracts of haemolymph on Sephadex LH-20 made possible the measurement of the titre of adipokinetic hormone in the haemolymph of locusts. Experimentally produced high concentrations of haemolymph carbohydrate caused a delay in the mobilization of lipid during flight, and very low titres of the hormone were present in the haemolymph of locusts injected with trehalose immediately before a 25 min flight. In these locusts flight speed was higher than saline-injected controls. Although delayed lipid mobilization during flight was also seen in locusts injected with sucrose, sucrose is not utilized for flight metabolism and flight speed was not increased by the injection. Tentative estimates of the release rate (c. 1000pg/20min flight) and half life (c. 20 min) of adipokinetic hormone during flight are made. The results described suggest that during flight the rate at which trehalose disappears from the haemolymph does not play a major role in the initiation of the release of adipokinetic hormone.     

The strength of selection in the context of migration speed

I use a model of avian migration based on maximization of overall migration speed to compare the strength of selection acting on foraging performance and flight speed. Let the optimal foraging behaviour be u* and the optimal flight speed be v*. It is shown that at this optimum, the ratio of the strength of selection on foraging to the strength of selection on flight speed is theta = -(u*2Pgamma"/v*2gammaP"), where gamma is the rate of energy expenditure during flight and P is the rate at which energy is gained during foraging. The dimensionless ratio P/gamma is the ratio of time spent building up fuel to time spent flying which A. Hedenström and T. Alerstam showed was much greater than unity. Although theta depends on this ratio, it also depends on the curvatures of the functions, as represented by gamma" and P". I use this simple example to make some general points about the strength of selection.     

Flight speeds and climb rates of Brent Geese: mass-dependent differences between spring and autumn migration

Aerodynamic theories of bird flight predict that horizontal flight speed will increase with increasing load whereas vertical flight speed will decrease. Horizontal flight speed for birds minimizing overall time on migration is predicted to be higher than flight speed for birds minimizing energy expenditure. In this study we compare flight speeds of Brent Geese Branta b. bernicla recorded by tracking radar and optical range finder during spring and autumn migration in southernmost Sweden, testing the above-mentioned predictions. Geese passing Sweden in spring are substantially heavier than in autumn and there might also be a stronger element of time-selection in spring than in autumn. Recorded airspeeds were significantly higher in spring (mean 19.0 m s⁻¹) than in autumn (mean 17.3 m s⁻¹), the average difference being slightly larger than predicted due to the mass difference alone. The effects on airspeed of wind, vertical speed, flock size and altitude were also analysed, but none of these factors could explain the seasonal difference in airspeed. Hence, the results support the hypothesis of mass-dependent flight speed adjustment. The difference between the two seasons was not large enough to corroborate the hypothesis of a stronger element of time-selection in spring, but this hypothesis cannot be rejected. Vertical flight speeds were lower in spring than in autumn, supporting a negative effect of load on birds' flight power margin.     

Flight style in bats as predicted from wing morphometry: the effects of specimen preservation

An as yet unconsidered potential error in studies that predict flight style from morphological measurements of bats is the effect of the specimen type employed. On the basis of the finding that morphological measurements taken from fluid-preserved bat specimens may not yield values equivalent to those taken from the live animal, we compared the values of several variables (lifting surface area, wingspan, mass, aspect ratio, wing loading and minimum power speed) for live and fluid-preserved little brown bats ( Myotis lucifugus ) with the accepted standards for this species given by Norberg & Rayner (1987). Significant differences were detected for lifting surface area, wingspan, mass, aspect ratio and wing loading values taken from live bats and their respective values reported by Norberg & Rayner. Differences between preserved bats and Norberg & Rayner's numbers were limited to lifting surface area and wingspan (extended wing positions only), aspect ratio (all wing positions), and mass (both 70% ethanol- and 45% isopropyl alcohol-preserved specimens). Thus, Norberg & Rayner's values correspond most closely to values obtained from preserved museum specimens, a fact reflecting the source of their data in this instance. This and other limitations involved in attempting to predict the flight style of bats from a few morphological characters are discussed.