Increased Wing Loading Research Articles

Beyond winglets: evolutionary scaling of flight-related morphology in stick insects (Phasmatodea)

Abstract The first winged insects evolved from a wingless ancestor, but details of the transition to a fully-winged morphology remain unclear. Studying extant pterygotes with partial wings, such as the stick insects (order Phasmatodea), may help us to understand such a transition. Here, we address how a series of flight-related morphological parameters may correlate with flight evolution by studying different phasmids representing a volancy continuum ranging from miniaturized to full-sized wings. Variation in phasmid wing shape, venation, wing mass and the mass of flight muscle can be described by specific scaling laws referenced to wing length and wing loading. Also, the mass distribution of the body-leg system is conserved in spite of a wide range of variation in body shape. With reduced wing size and increased wing loading, the longitudinal position of the wing-bearing thoracic segments is shifted closer to the insects’ centre of body mass. These results demonstrate complex reconfiguration of the flight system during wing morphological transitions in phasmids, with various anatomical features potentially correlated with reduced flight performance attained with partial wings. Although these data represent phasmid-specific features of the flight apparatus and body plan, the associated scaling relationships can provide insight into the functionality of intermediate conditions between wingless and fully-winged insects more generally.

Domestic egg-laying hens, Gallus gallus domesticus, do not modulate flapping flight performance in response to wing condition.

Wild birds modulate wing and whole-body kinematics to adjust their flight patterns and trajectories when wing loading increases flight power requirements. Domestic chickens (Gallus gallus domesticus) in backyards and farms exhibit feather loss, naturally high wing loading, and limited flight capabilities. Yet, housing chickens in aviaries requires birds to navigate three-dimensional spaces to access resources. To understand the impact of feather loss on laying hens' flight capabilities, we symmetrically clipped the primary and secondary feathers before measuring wing and whole-body kinematics during descent from a 1.5 m platform. We expected birds to compensate for increased wing loading by increasing wingbeat frequency, amplitude and angular velocity. Otherwise, we expected to observe an increase in descent velocity and angle and an increase in vertical acceleration. Feather clipping had a significant effect on descent velocity, descent angle and horizontal acceleration. Half-clipped hens had lower descent velocity and angle than full-clipped hens, and unclipped hens had the highest horizontal acceleration. All hens landed with a velocity two to three times greater than in bird species that are adept fliers. Our results suggest that intact laying hens operate at the maximal power output supported by their anatomy and are at the limit of their ability to control flight trajectory.

An experimental increase in female mass during the fertile phase leads to higher levels of extra-pair paternity in pied flycatchers Ficedula hypoleuca

Female mass in most altricial birds reaches its maximum during breeding at egg laying, which coincides temporally with the fertile phase when extra-pair paternity (EPP) is determined. Higher mass at laying may have two different effects on EPP intensity. On the one hand, it would lead to increased wing loading (body mass/wing area), which may impair flight efficiency and thereby reduce female’s capacity to resist unwanted extra-pair male approaches (sexual conflict hypothesis). On the other hand, it would enhance female condition, favouring her capacity to evade mate guarding and to search for extra-pair mates (female choice hypothesis). In both cases, higher female mass at laying may lead to enhanced EPP. To test this prediction, we reduced nest building effort by adding a completely constructed nest in an experimental group of female pied flycatchers (Ficedula hypoleuca). Our treatment caused an increase in mass and thereby wing loading and this was translated into a significantly higher EPP in the manipulated group compared with the control group as expected. There was also a significant negative relationship between EPP and laying date and the extent of the white wing patch, an index of female dominance. More body reserves at laying mean not only a higher potential fecundity but a higher level of EPP as well. This interaction had not previously received due attention but should be considered in future studies of avian breeding strategies. While most research has been focused on determining possible criteria for extra-pair mate choice by females, less effort has been made on establishing if female traits are related to EPP and its intensity. One such trait is mass at laying which attains its highest level for breeding females of altricial birds. Our study indicates that a higher mass during the fertile phase not only has implications for female fecundity and predation risk but also for EPP in the resulting brood as more mass means a higher EPP.

Elevated temperatures translate into reduced dispersal abilities in a natural population of an aquatic insect

Rising global temperatures force many species to shift their distribution ranges. However, whether or not (and how fast) such range shifts occur depends on species' dispersal capacities. In most ecological studies, dispersal-related traits (such as the wing size or wing loading in insects) are treated as fixed, species-specific characteristics, ignoring the important role of phenotypic plasticity during insect development. We tested the hypothesis that dispersal-related traits themselves vary in dependence of ambient environmental conditions (temperature regimes, discharge patterns and biotic interactions during individual development). We collected data over 8years from a natural population of the crane fly Tipula maxima in central Germany. Using linear mixed-effect models, we analysed how phenotypic traits, phenological characteristics and population densities are affected by environmental conditions during the preceding 3, 6 and 12months. We found a moderate (5.6%) increase in wing length per 1°C increase in mean annual temperatures during the previous year. At the same time, body weight increased by as much as 17.8% in females and 26.9% in males per 1°C, likely driven by increased habitat productivity, which resulted in a 16.4% (female) and 19.3% (male) increased wing loading. We further found a shorter, more synchronized emergence period (i.e. a narrower time frame for dispersal) with increasing temperatures. Altogether, our results suggest that dispersal abilities of T.maxima were negatively affected by elevated temperatures, and we discuss how similar patterns might affect the persistence of populations of other aquatic insects, especially stenoecious taxa with narrow distribution ranges. Our study calls for integration of information on temperature-induced phenotypic plasticity of dispersal-related traits into models forecasting range shifts in the face of climate change. Furthermore, the patterns reported here are likely to affect metapopulation dynamics of aquatic insects under climate change conditions and may contribute to the ongoing decline of insect biomass and diversity.

Inspiration for wing design: how forelimb specialization enables active flight in modern vertebrates.

Harnessing flight strategies refined by millions of years of evolution can help expedite the design of more efficient, manoeuvrable and robust flying robots. This review synthesizes recent advances and highlights remaining gaps in our understanding of how bird and bat wing adaptations enable effective flight. Included in this discussion is an evaluation of how current robotic analogues measure up to their biological sources of inspiration. Studies of vertebrate wings have revealed skeletal systems well suited for enduring the loads required during flight, but the mechanisms that drive coordinated motions between bones and connected integuments remain ill-described. Similarly, vertebrate flight muscles have adapted to sustain increased wing loading, but a lack of in vivo studies limits our understanding of specific muscular functions. Forelimb adaptations diverge at the integument level, but both bird feathers and bat membranes yield aerodynamic surfaces with a level of robustness unparalleled by engineered wings. These morphological adaptations enable a diverse range of kinematics tuned for different flight speeds and manoeuvres. By integrating vertebrate flight specializations-particularly those that enable greater robustness and adaptability-into the design and control of robotic wings, engineers can begin narrowing the wide margin that currently exists between flying robots and vertebrates. In turn, these robotic wings can help biologists create experiments that would be impossible in vivo.

SIMILARITIES AND DIFFERENCES IN ALTITUDINAL VERSUS LATITUDINAL VARIATION FOR MORPHOLOGICAL TRAITS INDROSOPHILA MELANOGASTER

Understanding how natural environments shape phenotypic variation is a major aim in evolutionary biology. Here, we have examined clinal, likely genetically based variation in morphology among 19 populations of the fruit fly (Drosophila melanogaster) from Africa and Europe, spanning a range from sea level to 3000 m altitude and including locations approximating the southern and northern range limit. We were interested in testing whether latitude and altitude have similar phenotypic effects, as has often been postulated. Both latitude and altitude were positively correlated with wing area, ovariole number, and cell number. In contrast, latitude and altitude had opposite effects on the ratio between ovariole number and body size, which was negatively correlated with egg production rate per ovariole. We also used transgenic manipulation to examine how increased cell number affects morphology and found that larger transgenic flies, due to a higher number of cells, had more ovarioles, larger wings, and, unlike flies from natural populations, increased wing loading. Clinal patterns in morphology are thus not a simple function of changes in body size; instead, each trait might be subject to different selection pressures. Together, our results provide compelling evidence for profound similarities as well as differences between phenotypic effects of latitude and altitude.

Bat flight with bad wings: is flight metabolism affected by damaged wing membranes?

Infection of North American bats with the keratin-digesting fungus Geomyces destructans often results in holes and ruptures of wing membranes, yet it is unknown whether flight performance and metabolism of bats are altered by such injuries. I conducted flight experiments in a circular flight arena with Myotis albescens and M. nigricans individuals with an intact or ruptured trailing edge of one of the plagiopatagial membranes. In both species, individuals with damaged wings were lighter, had a higher aspect ratio (squared wing span divided by wing area) and an increased wing loading (weight divided by wing area) than conspecifics with intact wings. Bats with an asymmetric reduction of the wing area flew at similar speeds to conspecifics with intact wings but performed fewer flight manoeuvres. Individuals with damaged wings showed lower metabolic rates during flight than conspecifics with intact wings, even when controlling for body mass differences; the difference in mass-specific metabolic rate may be attributable to the lower number of flight manoeuvres (U-turns) by bats with damaged wings compared with conspecifics with intact wings. Possibly, bats compensated for an asymmetric reduction in wing area by lowering their body mass and avoiding flight manoeuvres. In conclusion, it may be that bats suffer from moderate wing damage not directly, by experiencing increased metabolic rate, but indirectly, by a reduced manoeuvrability and foraging success. This could impede a bat's ability to gain sufficient body mass before hibernation.

Predator escape tactics in birds: linking ecology and aerodynamics

In most birds, flight is the most important means of escape from predators. Impaired flight abilities due to increased wing loading may increase vulnerability to predation. To compensate for an increase in wing loading, birds are able to independently decrease body mass (BM) or increase pectoral muscle mass (PMM). Comparing nearshore and farshore foraging shorebird species, we develop a theory as to which of these responses should be the most appropriate. We hypothesize that nearshore foragers should respond to increased predation by increasing their PMM in order to promote speed-based escape. Instead, farshore foragers should decrease BM in order to improve agility for maneuvering escape. Experiments on 2 shorebird species are consistent with these predictions, but on the basis of the theoretical framework for evaluating effect size and biological significance developed here, more experiments are clearly needed.

The burden of motherhood: gliding locomotion in mammals influences maternal reproductive investment

Body mass is usually positively associated with reproductive output in females, with larger females having more offspring. However, in gliding or flying species, large body mass is constrained as a result of wing loading, defined as the ratio of body mass to the surface area available to generate lift. Gliding animals may be particularly susceptible to increased wing loading resulting from added mass during pregnancy. We compiled reproductive and morphological data for gliding and related nongliding mammals in all extant taxa where this type of locomotion occurs to test the predictions that gliders will have proportionally lighter litters than related nongliders, and relative litter mass will be negatively associated with wing loading. Contrary to our 1st prediction, gliders had heavier offspring than did nongliders in all taxa examined. Consistent with our 2nd prediction, however, greater relative litter mass was associated with lower wing loading. Maintaining the ability to glide when pregnant may influence investment in reproduction. However, gliding locomotion appears to be associated with increased litter mass, perhaps because of smaller litters of heavy young. Thus, we suggest that gliders may be characterized by K-selected life-history traits such as low mortality, slow metabolism, and fewer offspring per litter, but increased investment in individual young. The findings of this comparative study highlight how major shifts in locomotor mode can have a profound influence on patterns of life history.

Ecophysiological response to an experimental increase of wing loading in a pelagic seabird

The knowledge of ecophysiological responses in relation to foraging effort is crucial to understanding feeding strategies, survival and reproductive trade-offs, as well as to obtain reliable indicators of an excessive workload. We present an integrative approach that examines a suite of ecophysiological parameters in relation to increased workload. We experimentally increased wing loading of 10 Cory's shearwaters Calonectris diomedea, a medium-sized pelagic seabird, by adding 45 g extra weight and compared their ecophysiological responses with 10 control birds. Among all the parameters analysed, the only significant response to overloading was a longer foraging trip, a lower rate of mass gain whilst at sea, and an increase in plasma levels of creatine kinase and lactate dehydrogenase activity indicating muscular damage. The analyses on these muscular enzymes open new opportunities to measure the impact of instruments on birds and to understand physiological responses in relation to foraging activity.

The effects of wind speed, competition, and body size on perch height selection in a guild of Libellulidae species (Odonata)

For eleven species of sympatric libellulids, male mean mass was positively correlated with wing aspect ratio, wing loading, and mean perch height. We tested the hypo theses that perch height selection was governed by interspecific competition or biomechanical responses to increased wind speed at higher perches. Although larger odonates might prefer higher perches to offset their increased wing loading, species’ mean perch height did not correlate with changes in mean or maximum wind speeds. Rather, perch height selection is best explained by competitive interactions. Mean mass (log 10 transformed) of these species are distributed in a significantly non-random manner, consistent with community-wide character displacement. Also, observations of aggressive interactions and the response to decoys of three abundant species revealed a competitive hierarchy based on body size. Libellula luctuosa, the largest species, avoided stations with conspecific decoys but was attracted to sta tions with the decoys of two smaller species. L. incesta avoided stations with larger L. luctuosa decoys, but was attracted to stations with smaller Pachydiplax longipennis decoys. P. longipennis avoided stations with conspecific and L. incesta decoys. L. luctuosa was also more successful in displacing perchers (82.4%) than L. incesta (68.9%) and P. longipennis (46.6%). In pair-wise contrasts, the larger species was always more successful at displacing the smaller species. Finally, P. longipennis was attacked at significantly higher rates when it perched on high perches than when it perched at lower perches. We conclude that interspecific competition causes niche partitioning of perch height in this community.

Body building and concurrent mass loss: flight adaptations in tree sparrows.

Environmental changes are responsible for the evolution of flexible physiology and the extent of phenotypic plasticity in the regulation of birds' organ size has not been appreciated until recently. Rapid reversible physiological changes during different life-history stages are virtually only known from long-distance migrants, and few studies have focused on less extreme aspects of organ flexibility. During moult, birds suffer from increased wing loading due to wing-area reductions, which may impair flight ability. A previous study found that tree sparrows' escape flight (Passer montanus) is unaffected during moult, suggesting compensatory aptness. We used non-invasive techniques to study physiological adaptations to increased wing loading in tree sparrows. As wing area was reduced during natural moult the ratio of pectoral-muscle size to body mass increased. When moult was completed this ratio decreased. We show experimentally a novel, strategic, organ-flexibility pattern. Unlike the general pattern, where body mass is positively coupled to pectoral-muscle size, tree sparrows responded within 7 days to reductions in wing area by reducing body mass concurrently with an increase in pectoral-muscle size. This rapid flexibility in a non-migratory species probably reflects the paramount importance and long history of flight in birds.

Flight behaviour of seabirds in relation to wind direction and wing morphology

We studied flight direction relative to wind direction (hereafter referred to as “flight direction”), the relation between wing morphology and flight behaviour and interspecies relationships in flight behaviour among all major seabird taxa. We calculated wing loading and aspect ratios for 98 species from 1029 specimens. Species were sorted into 13 groups on the basis of similarity in patterns of flight direction. The primary flight direction of Pelecaniformes and Charadriiformes was into and across headwinds. The most common flight direction of Procellariiformes was across wind. Seabirds avoided flying with tailwinds. Wing loading and aspect ratios were positively correlated in Procellariiformes, Pelecaniformes and alcids but negatively correlated in larids. In Procellariiformes, incidence of headwind flight and that of tailwind flight were significantly correlated with wing loading and aspect ratio; species with higher wing loading and aspect ratios flew more often into headwinds and less often with tailwinds. In contrast, the proportion of Pelecaniformes and Charadriiformes flying with tailwinds increased significantly with increased wing loading. Our results demonstrate a close link in seabirds between flight behaviour, wing morphology and natural history patterns in terms of distribution, colony location, dispersal and foraging behaviour.

Change in Forearm Curvature Throughout the Summer in Female Big Brown Bats

Female Eptesicus fuscus , sampled biweekly from an attic roost in Byron, Shiawassee Co., Michigan, from 25 April through 26 September 1990, were aged, weighed, sexed, and photographed with left wing extended. From photographs, the following measurements were taken: length of forearm, distance from elbow to point of maximum radius curvature, displacement of radius at that point, width of wing at digit V, and length of wing tip. A significant curvilinear relationship was found over time for maximal curvature displacement of the radius. Forearm curvature decreases throughout pregnancy and most of lactation, and then increases until summer-roost abandonment. This arrangement may increase foraging efficiency by improving lift and maneuverability, and offset increased wing loading.

Effects of Age, Sex, and Fat Level on Wing Loading in Dark-Eyed Juncos

-Ageand sex-related variation in aerodynamically important traits such as wing loading may contribute to behavioral variation within a population. Increased wing loading also may be an important cost of carrying extra body fat, placing constraints on viable strategies of migratory and winter fattening. Therefore, we quantified the effects of age, sex, and fat level on wing loading in Dark-eyed Juncos (Junco hyemalis). Female juncos had significantly greater wing loading than males; wing loading did not differ among age classes. Increased fat levels (as indicated by fat scores) increased wing loading in all age/sex classes, but females and adults showed significantly greater fat-related increases in wing loading than males and immatures. Increasing from lean body mass to a full fat load added approximately 14 to 16% to an individual's wing loading. Wing loading increased allometrically with lean body mass in juncos (heavier individuals have relatively greater wing loading). We found sexand fatrelated variation in wing loading that is probably sufficient to affect flight performance and, therefore, susceptibility to predation, strategies of fattening, and distribution among individual Dark-eyed Juncos. Received 7 December 1990, accepted 10 January 1992. WING loading, a fundamental component of avian wing design, affects speed, maneuverability, and energy expenditure during flight (Rayner 1988, Pennycuick 1989, Norberg 1990 and references therein). Because wing loading is an important determinant of flight performance, interspecific differences (particularly large-scale taxonomic differences) in wing loading can be associated with ecological and behavioral variation among taxa (Greenewalt 1962, 1975, Norberg 1979, 1986, 1990:241, Norberg and Norberg 1988, Rayner 1988). Within species, wing loading can exhibit ageand sex-specific variation (e.g. Blem 1975, Mueller et al. 1981). Furthermore, widespread intraspecific variation in wing length (e.g. Alatalo et al. 1984) and wing shape (Gaston 1974, Tiainen and Hanksi 1985, Hedenstrom and Pettersson 1986, Mulvihill and Chandler 1990) suggests that variation in wing loading within species is common. This raises the possibility of ecologically significant covariation of aerodynamically important traits such as wing loading with foraging behavior, susceptibility to predation, or migratory dynamics within a population. We analyzed intraspecific variation in wing loading in a passerine bird, the Dark-eyed Junco 3Present address: Department of Biological Sciences, University of Southern Mississippi, Southern Station, Box 5018, Hattiesburg, Mississippi 39406, USA. (Junco hyemalis). Predicting the extent or direction of possible differences in wing loading among age/sex classes of juncos is difficult, because wing loading is the result of an interaction among body mass, wing length, and wing shape (all of which are characters that show ageand sex-related variation in juncos; Nolan and Ketterson 1983, Mulvihill and Chandler 1990). Furthermore, the body mass of juncos is subject to considerable temporal variation (e.g. during migratory or winter fattening) that will influence wing loading (Nolan and Ketterson 1983, Chandler and Mulvihill, unpubl. data). In fact, increased wing loading may be an important cost of carrying extra body fat (Blem 1975, Stuebe and Ketterson 1982, Nolan and Ketterson 1983), placing constraints on viable strategies of migratory or winter fattening (Lima 1986, Alerstam and Lindstr6m 1990). Because of the potential ecological significance of ageand sexspecific variation in wing loading, and the hypothesized role of increased wing loading in constraining migratory and winter fattening, our objectives were: (1) to quantify ageand sexrelated differences in wing area and wing loading among Dark-eyed Juncos; (2) to determine the aerodynamic cost (in terms of increased wing loading) of increasing fat levels in a passerine bird; and (3) to characterize the intraspecific relationship between wing loading and body mass.

Wing-loading, stability and morphometric relationships in flying fish (Exocoetidae) from the North-eastern Atlantic

‘Four-winged’ flying fish (in which both pectoral and pelvic fins are hypertrophied) reach greater maximum sizes than ‘two-winged’ forms in which only the pectoral fins are enlarged. Exocoetus obtusirostris shows negatively allometric growth in relation to standard length in terms of body mass (b=2·981), and lateral fin area (b=1·834). In consequence, wing-loading rises in positive allometric fashion with standard length (b=l·236). Pectoral fin length cannot be greater than 78–79% of standard length or swimming will be impaired, so the requirement for increased flying speed resulting from increased wing-loading during growth means that lift:drag ratios have to be improved by relatively narrowed wings and tapered wing tips; features which in turn increase wing-loading. Evidence is presented to show that hypertrophied pelvic fins in four-wingers are required to solve problems of stability in pitch, rather than to decrease wing-loading. The ‘non-flying’ flying fish, Oxyporhamphus micropterus, has very high wing-loadings, but the main reason that it cannot fly is that the centre of gravity of the fish is so far behind the pectoral fins that stalling on take-off would be inevitable. Flying fish possess reasonable quantities of red axial musculature, but no more than are used for cruising in fast-moving pelagic fish such as mackerel; it seems probable that acceleration to take-off speed in flying fish requires use of anaerobic white muscles.

A comparison of foraging at refuse tips by three species of gull (Laridae)

The comparative foraging of Black‐headed (Larus ridibundus), Herring (L. argentalus) and Great black‐backed gulls (L. marinus) was investigated at refuse tips in north‐east England. Between October and February, two races of Herring gulls are present, those which breed in Britain (L. a. argenteus) and the larger Scandinavian herring gulls (L. a. argentatus).Three types of feeding at a refuse tip were distinguished: undisturbed primary feeding (highly competitive feeding on freshly dumped rubbish), disturbed primary feeding (agile surface dipping for food from the air, close to the working bulldozer) and secondary feeding (low density feeding on dispersed and partially buried rubbish).In undisturbed feeding the largest individuals (i.e. Great black‐backed gulls) were competitively superior and achieved the highest feeding success. The smallest individuals (i.e. Black‐headed gulls) were rapidly excluded by the larger gulls. Scandinavian herring gulls were competitively superior in intraspecific interactions, but they were selectively attacked by Great black‐backed gulls. Disturbed feeding, in contrast, was used most by Black‐headed gulls and not at all by Great black‐backed gulls. Large body size is a disadvantage in disturbed feeding, due to increased wing loading acting as a constraint on manoeuvrability. Overall, the separation between species, in terms of the proportion of food gained by different feeding methods, was estimated at 30–50%.Cold and windy conditions led to increased numbers of Herring and Great black‐backed gulls at tips, and numbers of Great black‐backed gulls were also higher when fish landings at the coast were low. There were significant differences between tips in the number of Great black‐backed and Black‐headed gulls, possibly due to differences in working regime which influence the feeding opportunities which were available.

Flying-Boats and Their Possible Developments

The Author endeavours to indicate briefly the growth of flying—boats from their inception to the present day and to forecast their probable line of development in the future. It is shown that our present achievement has been arrived at after the comparatively short period of twenty—five years and an attempt has been made to indicate the type of flying—boat which might normally be expected to mature within the next decade.The water characteristics of a present—day hull are discussed and typical curves are included giving the resistance, attitude and the effect of applied moment for a flying—boat of approximately 40,000lb., all—up weight.Before proceeding to a detailed investigation into a particular case of a flying—boat of the future, the Author briefly describes the progress which has been made with regard to the engines and compares the relative advantages of the compression—ignition engine and the petrol engine.Reasons are given why the petrol engine still tends to retain its supremacy.For the future development the Author has taken the particular case of a flying—boat of 300,000lb. all—up weight and has attempted to analyse the probable structure weight of such an aircraft and what could reasonably be expected in the way of pay load and performance.The general conclusions are that the construction of such a boat would be possible, its structure weight by means of an increased wing loading could be maintained at the present—day figure and that its performance would materially increase.