Mixed patterns of morphological adaptation to insularity in an aerial displaying bird,the Common Snipe Gallinago gallinago

On islands, colonizing birds may evolve behavioural and morphological adaptations to the new environment, often resulting in changes in body size and reduction or even total loss of flight. These island populations have therefore been used to test hypotheses related to adaptations for flight. However, in certain species in which flight is used not only in foraging and migration but also in mating displays, disentangling the effects of natural and social selection is difficult. Thus, sedentary populations of species that perform aerial displays (such as the Common Snipe Gallinago gallinago that breed in the Azores archipelago) may offer an opportunity to separate the effects of natural and social selection on morphology. If insular Common Snipe respond to the characteristic ecological context of oceanic islands, we expect them to differ from migratory conspecifics in body size and by having relatively smaller and more rounded wings. On the other hand, if social selection exerts a more powerful force over the morphology of this species, we expect that sedentary and migratory birds will not differ in flight‐related characters. We tested these hypotheses by comparing morphological characters measured on live Common Snipe captured in the Azores during the breeding season with those measured on migratory specimens hunted during autumn/winter in mainland Portugal. Sedentary Azorean birds were smaller and had relatively shorter tails but did not show the tendency for insular birds to possess more rounded wings as described in other taxa, including in the Azores. Bergman's rule might explain the difference in body size and shorter tails may be responsible for behavioural differences between populations. The lack of difference in wing shape might be explained by the need of the Common Snipe to perform aerial displays during courtship, suggesting an effect of social selection on the migratory strategy of this species.     

Starlings can categorize symmetry differences in dot displays

Fluctuating asymmetry is an estimate of developmental stability and, in some cases, the asymmetry of morphological traits can reflect aspects of individual fitness. As asymmetry can be a marker for fitness, it has been proposed that organisms could use morphological asymmetry as a direct visual cue during inter- and intraspecific encounters. Despite some experimental evidence to support this prediction, the perceptual abilities of animals to detect and respond to symmetry differences have been largely overlooked. Studying the ability of animals to perceive symmetry and factors that affect this ability are crucial to assessing whether fluctuating asymmetry could be used as a visual cue in nature. In this study, we investigated the ability of wild-caught European starlings Sturnus vulgaris to learn to discriminate symmetry from asymmetry in random dot patterns through operant learning experiments. The birds did not possess a spontaneous preference for either symmetry or asymmetry. The birds learned a symmetry preference, although the learning process took longer than that previously reported for pigeons Columba livia and was more error prone. After being trained to discriminate symmetry differences in random dot patterns, birds successfully transferred their symmetry discrimination abilities to a set of novel stimuli that they had not previously seen. This indicates that starlings can form a mental categorization of visual stimuli on the basis of a somewhat generalized symmetry phenomenon. We discuss these findings in relation to the probability that birds use fluctuating asymmetry as a visual cue.     

Fast and fuel efficient? Optimal use of wind by flying albatrosses

The influence of wind patterns on behaviour and effort of free-ranging male wandering albatrosses (Diomedea exulans) was studied with miniaturized external heart-rate recorders in conjunction with satellite transmitters and activity recorders. Heart rate was used as an instantaneous index of energy expenditure. When cruising with favourable tail or side winds, wandering albatrosses can achieve high flight speeds while expending little more energy than birds resting on land. In contrast, heart rate increases concomitantly with increasing head winds, and flight speeds decrease. Our results show that effort is greatest when albatrosses take off from or land on the water. On a larger scale, we show that in order for birds to have the highest probability of experiencing favourable winds, wandering albatrosses use predictable weather systems to engage in a stereotypical flight pattern of large looping tracks. When heading north, albatrosses fly in anticlockwise loops, and to the south, movements are in a clockwise direction. Thus, the capacity to integrate instantaneous eco-physiological measures with records of large-scale flight and wind patterns allows us to understand better the complex interplay between the evolution of morphological, physiological and behavioural adaptations of albatrosses in the windiest place on earth.     

Escape flights of yellowhammers and greenfinches: more than just physics

Wintering birds increase their fat reserves throughout the day, and impaired escape performance is often considered to be an important cost of fat reserves. Since lifting a larger mass requires more energy, if birds escape at maximum power output, an increase in mass will impair the escape flight. In this study we did not find support for mass-dependent escape performance for yellowhammers, Emberiza citrinella, and greenfinches, Carduelis chloris, with natural daily mass increases of 7-8%. This suggests either that the birds were not performing at maximum output at dawn, when light, or that maximum power output was higher at dusk, when heavy. Either way, the birds seemed to be able to put more effort into their escape flight when heavier. In both species, when alarmed, birds took off significantly faster and at a steeper angle than when not alarmed. Yellowhammers escaped at a higher speed and angle than greenfinches, and reacted faster to the predator model. This suggests that predator escape is more than just Newtonian physics, and may be influenced by behavioural, as well as morphological, adjustments. Different species may have evolved different responses to predation risk. Our results seem to be in disagreement with recent ideas about mass-dependent predation risk. However, to build up reserves, birds have to increase exposure time, which increases predation risk. This cost may be more important than impaired escape performance when relatively small, daily, changes in body mass are considered. Copyright 2000 The Association for the Study of Animal Behaviour.     

Butterfly visual characteristics and ontogeny of responses to butterflies by a specialized tropical bird

The responses of two adult and three hand-reared, naive young rufous-tailed jacamars (Galbula ruficauda) to local butterflies were studied in feeding experiments. Four behavioural characteristics distinguish jacamars from other less specialized avian predators: (1) Exposed to butterflies for the first time, naive young jacamars would attack butterflies without showing signs of inhibition. Unacceptable butterflies, once captured, were taste-rejected quickly, and most survived the sampling. The few presumably unacceptable butterflies consumed by the birds were not observed to cause vomiting. (2) After gaining some familiarity with butterflies, young birds, like the adults, developed a reluctance to attack. They visually rejected certain classes of butterflies, often failing to attack them during an entire four-hour feeding trial. However, occasional attacks were made on butterflies in these ‘rejected’ classes. When this did occur, the insects proved to be actually easier to catch than those that were more often attacked. Once captured, however, the majority of these butterflies were taste-rejected. (3) For a given butterfly species, most individuals were either consumed or rejected. Thus, each species could be clearly classified as either acceptable or unacceptable to the jacamars. This consistency in jacamar responses resulted in a bimodal acceptability distribution of sympatric butterflies. (4) Young jacamars were capable of rapid associative learning and their responses were closely associated with butterfly visual characteristics in which colour pattern, flight behaviour, and morphology were also closely correlated. Thus, a single butterfly morphological parameter termed body shape (body length/thoracic diameter ratio) can adequately predict the feeding responses of jacamars. Visually detectable traits associated with butterflies possessing chemical defences may represent a balance between the need to signal unambiguously to specialized and/or experienced predators and the need to escape attacks by generalized and/or opportunistic predators. Since the proportion of specialized predators is higher in the tropical rainforest than in other habitat types, we expect greater divergence of morphological and behavioural characteristics between palatable and unpalatable butterflies in rainforest habitats.     

Phylogenetics and ecomorphology of emarginate primary feathers

Wing tip slots are a distinct morphological trait broadly expressed across the avian clade, but are generally perceived to be unique to soaring raptors. These slots are the result of emarginations on the distal leading and trailing edges of primary feathers, and allow the feathers to behave as individual airfoils. Research suggests these emarginate feathers are an adaptation to increase glide efficiency by mitigating induced drag in a manner similar to aircraft winglets. If so, we might expect birds known for gliding and soaring to exhibit emarginate feather morphology; however, that is not always the case. Here, we explore emargination across the avian clade, and examine associations between emargination and ecological and morphological variables. Pelagic birds exhibit pointed, high‐aspect ratio wings without slots, whereas soaring terrestrial birds exhibit prominent wing‐tip slots. Thus, we formed four hypotheses: (1) Emargination is segregated according to habitat (terrestrial, coastal/freshwater, pelagic). (2) Emargination is positively correlated with mass. (3) Emargination varies inversely with aspect ratio and directly with wing loading and disc loading. (4) Emargination varies according to flight style, foraging style, and diet. We found that emargination falls along a continuum that varies with habitat: Pelagic species tend to have zero emargination, coastal/freshwater birds have some emargination, and terrestrial species have a high degree of emargination. Among terrestrial and coastal/freshwater species, the degree of emargination is positively correlated with mass. We infer this may be the result of selection to mitigate induced power requirements during slow flight that otherwise scale adversely with increasing body size. Since induced power output is greatest during slow flight, we hypothesize that emargination may be an adaptation to assist vertical take‐off and landing rather than glide efficiency as previously hypothesized.     

Evolution of the wave: aerodynamic and aposematic functions of butterfly wing motion

Many unpalatable butterfly species use coloration to signal their distastefulness to birds, but motion cues may also be crucial to ward off predatory attacks. In previous research, captive passion-vine butterflies Heliconius mimetic in colour pattern were also mimetic in motion. Here, I investigate whether wing motion changes with the flight demands of different behaviours. If birds select for wing motion as a warning signal, aposematic butterflies should maintain wing motion independently of behavioural context. Members of one mimicry group (Heliconius cydno and Heliconius sapho) beat their wings more slowly and their wing strokes were more asymmetric than their sister-species (Heliconius melpomene and Heliconius erato, respectively), which were members of another mimicry group having a quick and steady wing motion. Within mimicry groups, wing beat frequency declined as its role in generating lift also declined in different behavioural contexts. In contrast, asymmetry of the stroke was not associated with wing beat frequency or behavioural context-strong indication that birds process and store the Fourier motion energy of butterfly wings. Although direct evidence that birds respond to subtle differences in butterfly wing motion is lacking, birds appear to generalize a motion pattern as much as they encounter members of a mimicry group in different behavioural contexts.     

The effects of a wind farm on birds in a migration point: the Strait of Gibraltar

The interaction between birds and wind turbines is an important factor to consider when a wind farm is constructed. A wind farm and two control areas were studied in Tarifa (Andalusia Province, southern Spain, 30STF590000–30STE610950). Variables were studied along linear transects in each area and observations of flight were also recorded from fixed points in the wind farm. The main purpose of our research was to determine the impact and the degree of flight behavioural change in birds flights resulting from a wind farm. Soaring birds can detect the presence of the turbines because they change their flight direction when they fly near the turbines and their abundance did not seem to be affected. This is also supported by the low amount of dead birds we found in the whole study period in the wind farm area. More studies will be necessary after and before the construction of wind farms to assess changes in passerine populations. Windfarms do not appear to be more detrimental to birds than other man-made structures.     

Energetics and metabolite profiles during early flight in American robins (Turdus Migratorius)

Although birds use fat as the primary fuel for migratory flights, carbohydrate and protein catabolism could be significant in the early stages of flight while pathways of fatty acid transport and oxidation are induced. The fuel mixture of long distance migrant birds can also be affected by the rate of water loss, where birds catabolize more protein to increase endogenous water production under dehydrating flight conditions. Despite many studies investigating flight metabolism, few have focused on the metabolic response to flight during the switchover to fat catabolism in migrants, and none have examined the effect of ambient conditions on fuel selection during early flight. We investigated the effect of water loss on the metabolic response to short duration flight in the American robin (Turdus migratorius). Birds were flown in a climatic wind tunnel and changes in body composition and plasma metabolites were measured. As flight duration increased, there was a gradual switchover from carbohydrate and protein catabolism to fat catabolism. Plasma metabolite profiles indicate that the mobilization of fat occurred within 20 min of initiating flight. Plasma glucose decreased and uric acid increased with flight duration. Ambient humidity did not affect fuel mixture. Thus, it seems that the utilization of fat may be delayed as migrants initiate flight. Short-hop migrants may exploit high rates of endogenous water production resulting from carbohydrate and protein catabolism early in flight to offset high water loss associated with low humidity. Rapid catabolism of lean body components at the start of a flight also reduces mass quickly, and may reduce energy costs.     

A new approach for the assessment of stochastic variation: analysis of behavioural response in blue mussel (Mytilus edulis L.)

One of the most effective techniques for evaluating stress is the analysis of developmental stability, measured by stochastic variation based particularly on fluctuating asymmetry, i.e. a variance in random deviations from perfect bilateral symmetry. However, the application of morphological methods is only possible when an organism lives under testing conditions during a significant part of its ontogenesis. Contrary to morphological characters, behavior can change very fast. Consequently, methods based on behavioural characters may have advantages over more traditional approaches. In this study we describe the technique of assessing stochastic variation, using not morphological, but behavioural characters. To measure stochastic variation of behavioural response, we assessed the stability of the isolation reaction of blue musselMytilus edulis at regular changes of salinity. With increasing temperature from +12°C to +20°C stochastic variation of the isolation reaction increased, which is a common response to change of environmental conditions. In this way, we have developed a method of assessing stochastic variation of behavioural response in molluscs. This method may find a great range of applications, because its usage does not require keeping animals in tested conditions for a long time.     

Evidence for a rule governing the avoidance of superfluous escape flights

When an imminent attack by a predator on a group of birds is signalled to non-detectors only by the departure of the detector, non-detectors may make time-wasting false-alarm flights in response to mistaken or non-predator-driven departures. The frequency of false-alarm flights might be reduced if group members assess the reason for single departures before responding. Immediate flights should only occur after multiple simultaneous departures, because these are only likely to be generated by an attack. The response delay between the detectors' departure and the next birds that respond should then be dependent on the number of detectors. On sparrowhawk attack, response delays in redshanks decreased significantly as detector number increased, controlling for raptor conspicuousness and proximity, and flock size and spacing. If response delay is modified because of risk dilution, it should increase with flock size and, consequently, the rate of alarm flights due to mistakes should decrease. However, response delay did not increase and flight frequency due to misidentification of non-raptors or non-predator-driven departures did not decrease with flock size. Significantly more feeding time was lost by birds in small flocks, suggesting that the dilution effect decreased the cost of each false-alarm flight rather than their frequency.     

Sleep in birds: lying on the continuum of activity and rest

Abstract

Sleep is highly organized activity which is associated with decreased muscular activity and reduced response to environmental stimuli. The sleep is regulated by both, circadian and homeostatic mechanisms. Sleep patterns can be studied by behavioral assays by observing different sleep behaviors or by neuronal activity such as EEG (electroencephalogram), EOG (electro-oculogram), and EMG (electromyogram). Sleep is organized into non-rapid eye movement (NREM) and rapid eye movement. The sleep pattern in birds are similar to that in mammals, however, few differences such as existence of unihemispheric sleep (UHS) in almost all birds compared to few marine mammals do exist. The UHS results in asymmetry of the brain function measured as slow wave activity (SWA). Several migrants exhibit sleeplessness and they compensate it by NREM. They employ UHS during their migratory flight to remain alert while sleeping and maintain the balance while flying which is advantageous for these birds. Thus, sleep is of fundamental significance for the animal as it lies on the continuum of activity and rest. The present review focuses on some of above mentioned facts about sleep in higher vertebrates particularly in birds.     

On the origin of avian flight: Compromise and system approaches

Based on evolutionary morphological analysis of the fore and hind limbs of extinct and extant birds, a new compromise hypothesis of the origin of flight in birds and theropod dinosaurs is proposed. The bipedalism and anisodactylous foot suitable for various functions were key adaptations for the development of flight. The bipedalism freed forelimbs from the supporting function and promoted transformation into wings, as animals moved from one tree branch to another and descended from trees. At the initial stage, the strong hind limbs provided the opportunity to climb and leap onto trees, bushes, or eminence, while the anisodactylous foot provided a firm support on both dry land and trees. The support provided by this foot allowed the reduction of the tail, which was initially composed of a long row of vertebrae. Thus, a stage of gliding flight was not necessarily passed by early birds. In the other lineages of feathered creatures, functional changes in forelimbs that resulted in the formation of wings developed in parallel and followed almost the same scenario.     

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.     

Sexual differences rather than flight performance underlie movement and exploration in a tropical butterfly

1. Individual movement behaviour governs several routine processes, and may scale up to important ecological processes, including dispersal. However, movement is affected by a wealth of factors, including abiotic conditions, flight performance, and behavioural traits. Although it has been historically assumed that insect flight is in the first place ruled by physiology and morphology, researchers have only recently begun to understand the potentially important role of behavioural traits. 2. This study aims to disentangle the relative importance of thermal conditions during development, and especially flight performance (capacity), versus behaviour (intrinsic motivation) in relation to movement attributes (i.e. time until take‐off, number of positions visited) under controlled laboratory conditions in the tropical butterfly Bicyclus anynana. 3. As predicted, links were found between flight performance (forced flight) and morphological traits (body size). However, this link was less pronounced for movement and exploratory behaviour, suggesting a more pronounced role of intrinsic motivation on the actual decision to move, or not. Thus, flight performance and movement may not be intimately associated. 4. Flight behaviour was mainly determined by sexual differences, with males showing better flight performance, higher mobility, and enhanced exploration than females. 5. Lower developmental temperatures increased thorax–abdomen ratio, thorax mass, and exploratory behaviour, and decreased wing loading. This may potentially aid flight capacity under thermally challenging conditions. 6. This study adds to the growing evidence that behavioural traits should not be neglected when investigating movement and dispersal, as they may well play a crucially important role.     

Courtship and genetic quality: asymmetric males show their best side

Fluctuating asymmetry (FA), the small random deviations from perfect morphological symmetry that result during development, is ubiquitous throughout the animal kingdom. In many species, FA seems to play a role in mate choice, perhaps because it signals an individual''s genetic quality and health. However, the relationship between an individual''s FA and behaviour is generally unknown: what do more asymmetric individuals do about their own asymmetry? We now show for the first time that individuals respond behaviourally to their own morphological FA in what appears to be an adaptive manner. During courtship, male guppies exhibiting high FA in ornamental colour, bias their displays towards their more colourful body side, thus potentially increasing their attractiveness by exaggerating the quantity of their orange signal. This appears to be a strictly behavioural male response to cues provided by females, as it does not occur when males court a non-reactive model female. Whether inferior males realize any mating advantage remains uncertain, but our study clearly demonstrates a behavioural response to random morphological asymmetries that appears to be adaptive. We propose that the tendency to show or otherwise use a ‘best side’ is common in nature, with implications for sexual signalling and the evolution of more pronounced asymmetries.     

Barb geometry of asymmetrical feathers reveals a transitional morphology in the evolution of avian flight

The geometry of feather barbs (barb length and barb angle) determines feather vane asymmetry and vane rigidity, which are both critical to a feather''s aerodynamic performance. Here, we describe the relationship between barb geometry and aerodynamic function across the evolutionary history of asymmetrical flight feathers, from Mesozoic taxa outside of modern avian diversity (Microraptor, Archaeopteryx, Sapeornis, Confuciusornis and the enantiornithine Eopengornis) to an extensive sample of modern birds. Contrary to previous assumptions, we find that barb angle is not related to vane-width asymmetry; instead barb angle varies with vane function, whereas barb length variation determines vane asymmetry. We demonstrate that barb geometry significantly differs among functionally distinct portions of flight feather vanes, and that cutting-edge leading vanes occupy a distinct region of morphospace characterized by small barb angles. This cutting-edge vane morphology is ubiquitous across a phylogenetically and functionally diverse sample of modern birds and Mesozoic stem birds, revealing a fundamental aerodynamic adaptation that has persisted from the Late Jurassic. However, in Mesozoic taxa stemward of Ornithurae and Enantiornithes, trailing vane barb geometry is distinctly different from that of modern birds. In both modern birds and enantiornithines, trailing vanes have larger barb angles than in comparatively stemward taxa like Archaeopteryx, which exhibit small trailing vane barb angles. This discovery reveals a previously unrecognized evolutionary transition in flight feather morphology, which has important implications for the flight capacity of early feathered theropods such as Archaeopteryx and Microraptor. Our findings suggest that the fully modern avian flight feather, and possibly a modern capacity for powered flight, evolved crownward of Confuciusornis, long after the origin of asymmetrical flight feathers, and much later than previously recognized.     

Effect of the unilateral activation of brain hemispheres on visceral pain sensitivity in BALB/c mice

A hemispheric asymmetry of the visceral pain sensitivity control was revealed in the BALB/c mice: animals with the left hemisphere inactivation did not differ from sham-operated control mice in respect to the pain response parameters. A right hemisphere inactivation reduced or suppressed the pain response. This suggests that the right hemisphere domineers in the visceral pain control.     

Risk‐taking and the evolution of mechanisms for rapid escape from predators

Flight initiation distance (FID) is the distance at which an individual animal takes flight when approached by a human. This behavioural measure of risk‐taking reflects the risk of being captured by real predators, and it correlates with a range of life history traits, as expected if flight distance optimizes risk of predation. Given that FID provides information on risk of predation, we should expect that physiological and morphological mechanisms that facilitate flight and escape predict interspecific variation in flight distance. Haematocrit is a measure of packed red blood cell volume and as such indicates the oxygen transport ability and hence the flight muscle contracting reaction of an individual. Therefore, we predicted that species with short flight distances, that allow close proximity between a potential prey individual and a predator, would have high haematocrit. Furthermore, we predicted that species with large wing areas and hence relatively low costs of flight and species with large aspect ratios and hence high manoeuvrability would have evolved long flight speed. Consistent with these predictions, we found in a sample of 63 species of birds that species with long flight distances for their body size had low levels of haematocrit and large wing areas and aspect ratios. These findings provide evidence consistent with the evolution of risk‐taking behaviour being underpinned by physiological and morphological mechanisms that facilitate escape from predators and add to our understanding of predator–prey coevolution.     

Lateralization of catecholaminergic and behavioral response to cerebral infarction in the rat.

The effects of left middle cerebral artery ligation on brain catecholamine concentrations and behavior were compared with those effects of right middle cerebral artery ligation which have previously been reported. Although the lesion caused by middle cerebral artery ligation appeared to be identical on the two sides, the animals with left hemispheric lesion showed no postoperative change in either mean spontaneous 24 hour activity or mean catecholamine concentrations in several areas of the brain. In marked contrast, as we have previously reported and was confirmed in the present study, the animals with a right hemispheric infarct are hyperactive for about 2 to 3 weeks after surgery and there is a significant decrease in mean norepinephrine concentrations in several brain regions. These studies have demonstrated a remarkable asymmetry in the behavioral and biochemical response to cerebral cortical infarction. It is uncertain whether this asymmetry reflects an underlying hemispheric difference in catecholaminergic or non-catecholaminergic neurons.