Flight Morphology Research Articles

Flight morphology in fragmented populations of a rare British butterfly, Hesperia comma

In modern landscapes, many populations of rare species are restricted to fragments of formerly extensive habitat. However, the potential for evolutionary changes in dispersal ability to occur within these fragmented populations has received little attention. We examined morphological traits associated with flight and reproduction in fragmented populations of the silver-spotted skipper butterfly, Hesperia comma. Investment in flight was measured as relative wing area and thorax mass, and investment in reproduction as relative abdomen mass. All measurements were made on individuals reared in a common environment. In the UK, Hesperia comma was once fairly widely distributed in southern and eastern England, but retracted to its smallest UK distribution in the 1970s and 1980s. It then partially re-expanded in the North and South Downs in S.E. England. We first compared traits from colonised and refuge sites 2.9–4.5 km apart, and found no differences in relative investment in flight or reproduction. There were, however, significant differences in both relative thorax and abdomen mass between regions >40 km apart. Populations with the highest relative investment in the thorax occurred in a region where population expansion has been most rapid. These results, in combination with other studies linking butterfly morphology to patch area and/or isolation, suggest that evolutionary responses to habitat fragmentation could be widespread. ©

The turning- and linear-maneuvering performance of birds: the cost of efficiency for coursing insectivores

To examine the performance compromises necessitated by adaptations for high efficiency in flight, such as highaspect ratio wings, the flight morphology and acceleration performance of a guild of coursing aerial insectivores (swifts andswallows) were compared with those of a guild of avian generalists. Though phylogenetic non-independence made inference ofadaptation difficult, biologically significant differences in aspect ratio and acceleration performance probably exist between thetwo groups of birds. A model of aerial insectivory is presented to illustrate the performance demands of this foraging methodand the impacts of the compromises between high efficiency in sustained flight and turning- and linear-maneuveringperformance.

Functional Morphology of Aquatic Flight in Fishes: Kinematics, Electromyography, and Mechanical Modeling of Labriform Locomotion

Synopsis. Labriform locomotion is the primary swimming mode for many fishes that use the pectoral fins to generate thrust across a broad range of speeds. A review of the literature on hydrodynamics, kinematics, and morphology of pectoral fin mechanisms in fishes reveals that we lack several kinds of morphological and kinematic data that are critical for understanding thrust generation in this mode, particularly at higher velocities. Several needs include detailed three-dimensional kinematic data on species that are pectoral fin swimmers across a broad range of speeds, data on the motor patterns of pectoral fin muscles, and the development of a mechanical model of pectoral fin functional morphology. New data are presented here on pectoral fin locomotion in Gomphosus varius, a labrid fish that uses the pectoral fins at speeds of 1-6 total body lengths per second. Three-dimensional kinematic data for the pectoral fins of G. varius show that a typical drag-based mechanism is not used in this species. Instead, the thrust mechanics of this fish are dominated by lift forces and acceleration reaction forces. The fin is twisted like a propeller during the fin stroke, so that angles of attack are variable along the fin length. Electromyographic data on six fin muscles indicate the sequence of muscle activity that produces antagonistic fin abduction and adduction and controls the leading edge of the fin. EMG activity in abductors and adductors is synchronous with the start of abduction and adduction, re? spectively, so that muscle mechanics actuate the fin with positive work. A mechanical model of the pectoral fin is proposed in which fin morphometrics and computer simulations allow predictions of fin kinematics in three dimensions. The transmission of force and motion to the leading edge of the fin depends on the mechanical advantage of fin ray levers. An integrative program of research is suggested that will synthesize data on morphology, physiology, kinematics, and hydrodynamics to under? stand the mechanics of pectoral fin swimming.

Why do Birds have Tails? The Tail as a Drag Reducing Flap, and Trim Control

Birds have tails, bats do not. Does this fundamental difference in flight morphology reveal a difference in flight capability, and if so are birds or bats better fliers? I use Munk's stagger theorem, and Prandtl's relation for the induced drag of a biplane to show that for a given lift, and given wingspan, the induced drag of the wing-tail combination is lower that the induced drag of a wing alone. However the same reduction in induced drag could be achieved by slightly increasing the wingspan. While increasing the wingspan reduces induced drag, it can also increase profile drag and wing inertia. Induced drag is dominant at low speeds and during turns. Profile drag dominates at high speeds. The tail allows birds to have the wings needed for efficient cruising and high speed flight (when the tail can be furled giving little drag), at the same time the tail can be spread at low speeds or during turns to reduce induced drag. The tail can play a role in maintaining stability and balance, and it appears that the stability of birds is tailored so that the tail is required to generate lift at low speeds, when the interaction between the wings and the tail can also most effectively reduce induced drag.

Correspondence Between Plight Morphology and Foraging Ecology in Some Palaeotropical Bats

Analysis revealed a tight, functionally appropriate relationship between the flight morphology and foraging ecology of bats on Lombok I., Indonesia, that crossed family-level phylogenetic relationships in some instances. While aspect ratio, wing loading and tip shape were all important in separating microbat foraging strategies on Lombok I., the megabats were arrayed on differences in wing loading and tip shape related to solitary versus colonial foraging strategies. Flight morphology is a useful tool for studying ecological structure in the organisation of megabat as well as microbat communities.

Sex and age variation in echolocation calls and flight morphology of Daubenton’s Bats Myotis daubentonii

Nous avons etudie la variation des cris d'echolocation et de la morphologie de l'aile du Murin de Daubenton, Myotis dauhentonii, dans l'ouest de la Pologne. Les individus d'un an ou moins emettaient des cris sonar legerement, mais d'une maniere significative, de plus basse frequence que ceux emis par des murins plus âges. Bien qu'une difference sexuelle dans les cris sonar ne se soit pas manifestee, il existait un dimorphisme de la taille corporelle. Les femelles etaient en moyenne plus grandes que les mâles en ce qui concerne l'envergure et la superficie des ailes. La longueur de l'aile comprenant les doigts et celle comprenant les bras etaient toutes deux plus grandes chez les femelles, et celles-ci etaient aussi plus lourdes que les mâles, d'une maniere significative

Echolocation, flight morphology and foraging strategies of some West African hipposiderid bats

We studied echolocation call structure, flight morphology and feeding behaviour of three hipposiderid bats (Asellia tridens, Hipposideros caffer and H. ruber: Chiroptera: Hipposideridae) in The Gambia during the wet season (July‐August). All three species emitted brief CF/FM echolocation calls. In A. tridens CF (constant frequency) frequencies between 108 and 122 kHz were recorded. This variation was caused mainly by sex and age difference in call frequencies: juveniles used lower frequencies than did adults, and males were lower in frequency than females. Among adults, CF frequency was related to forearm length in a polynomial manner. Asellia tridens is unusual for a microchiropteran in that males are larger than females: nevertheless this species follows the typical trend for bats using CF components in their calls in that males call at lower frequencies than do females. The spread in frequencies noted for A. tridens in group flight was not caused primarily by individual shifting their frequencies when flying in a group compared with when flying alone. Three bats were flown separately and then together in a small room. The hypothesis that bats shift emitted frequencies in group flight to minimize confusing their own echoes with those from conspecifies was not supported. Rather, we suggest each bat has a personal CF frequency determined by sex, age and size, and that the variation created by these factors reduces confusion with other bats' echoes during group flight. Bats of the genus Hipposideros were separated into two groups by discriminant analysis on flight morphology. The two groups showed little overlap of CF frequencies used in echolocation. Bats identified as H. ruber called with CF resting frequencies between 121 and 136 kHz, while H. caffer used 128–153 kHz. Our results support the classification of these bats into two sibling species. We compared the flight performance of A. tridens and H. ruber by flying bats through obstacle courses: H. ruber had a lower wing loading and was able to negotiate more complex arrays of obstacles than could A. tridens. In the wild, H. ruber fed in more cluttered situations than did A. tridens. Both species were feeding mainly on Coleoptera during the study period, and in H. ruber individuals with higher aspect ratios and longer wingspans tended to eat more months than did bats with broader and shorter wings.

On the aerodynamics of animal flight in ground effect

Flight in ground effect above a flat, smooth surface may give an animal considerable performance advantages, including a reduction in cost of transport of up to 15%, and a reduction in mechanical flight power of as much as 35%, compared with values for flight out of ground effect. Previous theories modelling the phenomenon have either been incomplete or marred by typographical errors. A complete lifting line theory of flight in ground effect with a fixed wing is developed, and instructions are given so that it may be applied to animals such as skimmers, pelicans and myotid bats which fly and forage close above water. Several predictions are made about likely flight behaviour in ground effect, and about the appropriate flight morphology for taking advantage of the potential performance improvements. The most important conclusion, differing from previous analyses, is that slow flight performance in ground effect is very poor, owing to the horizontal air velocity induced around the wing in the presence of the ground.

Echolocation Ecology and Flight Morphology of Insectivorous Bats (Chiroptera) in South-Western Australia

A small community of obligate insectivorous microchiropterans in the Perup forest reserve of southwestern Australia was sampled to determine species flight morphologies, diets and echolocation call designs. The aspect ratio:wing loading relationships of the seven species analysed indicate a loose clustering of species into closed, edge and open microhabitats with substantial interspecific overlap. Non-parametric correlations of the bats' aspect ratios and wing loadings with their echolocation call characteristics support these foraging zone classifications. Diet analyses indicate that this community of bats forages on a wide variety of insects, although certain preferences for Lepidoptera, Hymenoptera and Coleoptera were noted. We use these results and observations of the same species from other sites to propose a microhabitat separation for the bats of the Perup forest.

Flight morphology of Neotropical butterflies: palatability and distribution of mass to the thorax and abdomen.

We test whether palatability of Neotropical butterflies is associated with distribution of mass to the thorax and abdomen. Thoracic mass is predominantly muscle mass, whereas abdominal mass includes organs of digestion, food storage, and reproduction. To escape from predation, butterflies palatable to the rufous-tailed jacamar (Galbula ruficauda) use fast, erratic flight, whereas unpalatable butterflies have defensive chemicals and slow, regular flight patterns. We adjusted for effects of phylogeny and report partial correlations for two levels of analysis: 1) comparisons among-lineage means, which test for correlations between traits of distantly related lineages, and 2) comparisons among deviations from lineage means (or within lineages), which test for correlations between traits of more closely related species.Among lineages for both males (n=10 lineages) and females (n=9), palatability and thoracic mass were positively correlated, whereas palatability and abdominal mass were negatively correlated. An inverse correlation between thoracic and abdominal mass is a consequence of the two segments composing 75% of the total body mass. Predation, indexed by palatability, may select for increased flight speed and thoracic mass at the expense of the abdomen, but relative flight speed and thoracic mass were not significantly correlated.Within lineages (n=45 species for each sex), thoracic mass was uncorrelated with palatability in both sexes. Relative flight speed correlated positively with thoracic mass and negatively with body mass. Palatability and abdominal mass were negatively correlated for males but not females. Hence differences between the sexes in mass distribution suggest differences in reproductive constraints and predation stress.

Ecological morphology and flight in bats (Mammalia; Chiroptera): wing adaptations, flight performance, foraging strategy and echolocation

Ecological morphology and flight in bats (Mammalia; Chiroptera): wing adaptations, flight performance, foraging strategy and echolocation

Evolutionary Convergence in Foraging Niche and Flight Morphology in Insectivorous Aerial-Hawking Birds and Bats

Some insectivorous birds and most insectivorous bats catch their prey in flight. This puts large demands on flight manoeuvrability and agility and calls for specialized adaptations in wing design. Aerial foraging is facilitated by low body mass and low wing loading, permitting high manoeuvrability and slow flight. Birds and bats with similar ecological foraging modes (aerial-foraging in open spaces or among vegetation) show strong convergence in wing shape. Birds foraging in open areas (swifts, swallows) show similarities with open-field foraging bats, whereas birds hunting among or close to vegetation (flycatchers, Nightjar) are more like bats hawking near or within vegetation. The specific flight costs are lower (because of higher wing aspect ratios) in all the bats and in those birds that hawk insects in open areas than in birds that hawk among vegetation or that do not hawk insects in the air at all. The latter group is rather different from aerial-hawking birds and bats in wing design.

Structure of Bat Guilds in the Kimberley Mangroves, Australia

(1) Deterministic guilds have been predicted to occur in stable, persistent communities. Mangrove communities in the Kimberley of Western Australia include large, isolated stands that are stable in terms of floristic composition and vegetation structure. A selection of stands was sampled for bats belonging to the insect foraging guild. (2) The potential foraging niche of each bat species was estimated in terms of the bat's flight morphology (aerodynamic characteristics) at minimum wing loading. These estimates were used to analyse the structure of the guild observed in each mangrove stand. (3) The observed guilds had a deterministic structure. The flight morphologies of species that foraged in the same stand showed almost no overlap even though each of these observed guilds occupied almost the same total area of morphological space as the entire pool of potential colonizers. In contrast, guild structures generated stochastically from the pool of potential colonizers included significant overlap. (4) Available flight space in the mangal was arbitrarily divided into five foraging microhabitats so that species' realized foraging niches could be estimated from field observations and used to interpret the morphological analysis. (5) Differences in species' flight morphologies could be related to vertical and horizontal foraging microhabitats but the morphological data indicated that a narrower partitioning of foraging zones actually occurred.

Morphometrics, Conductance, Thoracic Temperature, and Flight Energetics of Noctuid and Geometrid Moths

Geometrid moths in our sample differ from noctuid moths in that they have larger wings relative to their body and are smaller in body mass. As a consequence of their smaller mass, thoracic conductance of geometrids is greater than that of noctuids. Wing stroke frequencies increased with body mass and wing loading in both families. Therefore, it is likely that heat production during flight increases with body mass for these moths. Geometrids exhibited similar thoracic temperature excesses ($T_{th}$- $T_{a}$) of about 5-9 C, regardless of $T_{a}$ between $T_{a}$'s of 11 and 22 C. In noctuids, ($T_{th}$ - $T_{a}$) was greater at low $T_{a}$ than high $T_{a}$ (12 C at $T_{a}$ = 11 C; 7 C at $T_{a}$ = 22 C), suggesting that thermoregulation occurs during flight. Differences in flight performance and thermoregulation were correlated with flight morphology in the two families. Geometrids are capable of immediate flight and are erratic fliers, and high levels of thoracic heat loss coupled with low levels of heat ...

Flight Energetics and Heat Exchange of Gypsy Moths in Relation to Air Temperature

ABSTRACT Gypsy moths elevate thoracic temperature (Tth) during flight by endogenous heat production but do not regulate it. Thoracic temperature of moths in free, near-hovering flights exceeded air temperature by approximately 6–7 °C at all Ta’s between 17 and 32 °C. Mean rates of mass specific oxygen consumption varied between 40 and 47 ml O2 (g·h) −1 and were not correlated with air temperature. Wing-beat frequency increased from 27 to 33 (s) −1 between air temperatures of 18 and 35 °C. Thoracic heating and cooling constants are similar in live and dead moths, and removal of thoracic scales increases heating constants by about 12%. Preflight warm-up occurs at low Ta’s but the moths are capable of immediate, controlled flight at Ta’s above 22 °C. Relatively low levels of heat production by the flight muscles are a consequence of low power requirements associated with the flight morphology of gypsy moths. Calculated rates of thoracic and respiratory heat loss of free-flying moths are slightly lower than values of heat production.