Flight Initiation Research Articles

Variability in the area, energy and time costs of wintering waders responding to disturbance

Birds’ responses to human disturbance are interesting due to their similarities to anti‐predator behaviour, and understanding this behaviour has practical applications for conservation management by informing measures such as buffer zones to protect priority species. To understand better the costs of disturbance and whether it will impact on population size, studies should quantify time‐related responses as well as the more commonly reported flight initiation distance (FID). Using waders wintering on an estuarine area, we experimentally disturbed foraging birds on the Wash Embayment, UK, by walking towards them and recording their responses (FID, alert time, time spent in flight, time taken to resume feeding, and total feeding time lost). We present data for 10 species of conservation concern: Curlew Numenius arquata, Oystercatcher Haematopus ostralegus, Bar‐tailed Godwit Limosa lapponica, Grey Plover Pluvialis squatarola, Redshank Tringa totanus, Knot Calidris canutus, Turnstone Arenaria interpres, Ringed Plover Charadrius hiaticula, Sanderling Calidris alba and Dunlin Calidris alpina. Larger species responded more strongly, response magnitude was greater under milder environmental conditions, and responses varied over both small and large spatial scales. The energetic costs of individual responses, however, were low relative to daily requirements and disturbance events were unlikely to be frequent enough to seriously limit foraging time. We suggest, therefore, that wintering wader populations on the Wash are not currently significantly negatively impacted by human disturbance during the intertidal foraging period. This is also likely to be the case at other estuarine sites with comparable access levels, visitor patterns, invertebrate food availability and environmental conditions.

Environmental and biological drivers of flight initiation in a sporadic pest, Rutherglen bug, Nysius vinitor Bergroth (Hemiptera: Orsillidae)

Flight initiation is fundamental to insect dispersal. Insights into the meteorological and environmental drivers of flight initiation, and their relative importance, can therefore help determine the conditions under which mass dispersal events may occur. In relation to insect pestmanagement, the ability to anticipate such events would allow us to predict mass colonisation of crops and better manage outbreaks of an insect pest. This study insects aims to better predict flight initiation of Rutherglen bug, Nysius vinitor, and thus crop outbreaks originating from over-winter weed hosts. We examined the influence of temperature in combination with sex and the availability of food and water, under controlled environment conditions inside a flight chamber. Most of the variation in flight initiation was explained by temperature. We found that warm temperatures are required for flight initiation: the lower flight threshold was determined as 21 degrees C, the optimum temperature for flight as 25 degrees C and the upper flight threshold as 28 degrees C, fitting a quadratic distribution. However, additional data shows that such thresholds are not limiting: when N. vinitor is under extreme heat stress (35-40 degrees C) for a short period, they have a very high propensity to take-off. The rate of flight initiation was fastest within the first 5 h in both males and females for all tested temperatures. A lack of food and water resulted in a faster take-off rate of males, but had no effect on female flight initiation. Application of our analysis to temperature data in New South Wales (NSW) and Queensland (Qld), Australia, indicates that flight initiation in N. vinitor is likely to be highly seasonal, with very little flight activity expected in winter in eastern Australia. We found a longer suitable flight period and a greater number of suitable flight days per month in Qld compared to NSW. Such estimates could be used to inform regional pest arrival forecasts, integrated pest management decisions and the development of dispersal simulation models for this pest.

Trophy hunting and perceived risk in closed ecosystems: Flight behaviour of three gregarious African ungulates in a semi-arid tropical savanna

Although being an important conservation tool in Africa, trophy hunting is known to influence risk perception in wildlife species, thus affecting the behaviour and fitness of most targeted species. We studied the effects of trophy hunting on the flight behaviour of impala (Aepyceros melampus), greater kudu (Tragelaphus strepsiceros) and sable (Hippotragus niger) in two closed ecosystems, Cawston Ranch (hunting area) and Stanley and Livingstone Private Game Reserve (tourist area), western Zimbabwe. Using standardized field procedures, we assessed the flight behavioural responses of the three species in two seasons: non-hunting (December–March) and hunting (April–November) between March 2013 and November 2014. We tested the effect of habitat, group size, sex, season, start distance and alert distance on flight initiation distance using linear mixed models. Habitat, group size sex and alert distance did not have any effect on flight initiation distance for the three species. The three species were more alert and displayed longer flight initiation distances in the hunting area compared with the tourist area. Flight initiation distances for the three species were higher during the hunting season for the hunting area and low during the non-hunting season. Flight distances of the three species did not differ between the hunting area and the tourist area. We concluded that trophy hunting increased perceived risk of wild ungulates in closed hunting areas, whereas ungulates in non-hunting areas are less responsive and somehow habituated to human presence. Management plans should include minimum approach distances by tourists as well as establishing seasonal restrictions on special zones to promote species viability. Research aimed at integrating behavioural responses with physiological aspects of target species should be promoted to ensure that managers are able to deal with the behavioural trade-offs of trophy hunting at local and regional scale.

Fleeing to refuge: Escape decisions in the race for life

Economic escape theory that predicts that flight initiation distance (FID=predator-prey distance when a prey begins to flee from an approaching predator) increases as predation risk increases has been overwhelmingly supported. However, the vast majority of empirical tests have focused on effects of single predation risk factors. Even studies that have included multiple risk factors have not predicted how they jointly affect FID. I present a model that predicts joint effects of several predation risk factors that affect the outcome of a race between predator and prey to the prey's refuge. As a prey's distance to refuge and predator attack speed increase, and as the prey's location forces it to flee more toward a predator to reach refuge, FID increases. A published model proposed and experiment showed that FID is longer when prey flee directly toward than directly away from a predator to a refuge. We present a new geometric model that predicts FID for all angles between the prey's and predator's paths to refuge, distance of the prey from refuge when escape begins, predator and prey speeds, and a margin of safety allowing the prey to reach refuge before the predator. The model provides many new, testable predictions about relationships among its variables and FID. Most notably, it predicts that FID increases sigmoidally as the angle between predator and prey paths to refuge increases. Although the model is not economic (cost-benefit), we discuss its relationship to economic escape theory.

A test on within-individual changes in risk-taking behaviour due to experience to predation in the Collared Flycatcher (Ficedula albicollis)

Summary Different experiences from the past may have influence on individual’s behaviour through feedback mechanisms that can weaken or preserve the within-individual consistency of behavioural traits. Here, we aimed to find evidence for such feedback mechanisms that may operate on risk-taking behaviour via the effect of former experience to potential predation events in male Collared Flycatchers (Ficedula albicollis). We predicted that risk-taking of males would decrease after experiencing a predator’s attack in previous breeding seasons (negative feedback). We assessed risk-taking by flight initiation distance (FID) that is the distance at which an individual flees from an approaching predator, which was estimated for 234 individuals from different breeding seasons. Information on predation experience (i.e. occurrence of nest predation, the incidence of capture by human observers) was available from our long-term database on individual life histories. In a horizontal approach, we found no difference in FID when comparing males with former experience to predation with males naive to predators. A longitudinal approach relying on the repeated tests of the same individuals from different years yielded analogous results, we could not show a significant change in the risk-taking behaviour of the males as a consequence of experience to predation in past years. However, we found that individuals systematically took less risk over the years, which might be a consequence of acquiring general experience with age.

Genetic and Environmental Control of Neurodevelopmental Robustness in Drosophila.

Interindividual differences in neuronal wiring may contribute to behavioral individuality and affect susceptibility to neurological disorders. To investigate the causes and potential consequences of wiring variation in Drosophila melanogaster, we focused on a hemilineage of ventral nerve cord interneurons that exhibits morphological variability. We find that late-born subclasses of the 12A hemilineage are highly sensitive to genetic and environmental variation. Neurons in the second thoracic segment are particularly variable with regard to two developmental decisions, whereas its segmental homologs are more robust. This variability “hotspot” depends on Ultrabithorax expression in the 12A neurons, indicating variability is cell-intrinsic and under genetic control. 12A development is more variable and sensitive to temperature in long-established laboratory strains than in strains recently derived from the wild. Strains with a high frequency of one of the 12A variants also showed a high frequency of animals with delayed spontaneous flight initiation, whereas other wing-related behaviors did not show such a correlation and were thus not overtly affected by 12A variation. These results show that neurodevelopmental robustness is variable and under genetic control in Drosophila and suggest that the fly may serve as a model for identifying conserved gene pathways that stabilize wiring in stressful developmental environments. Moreover, some neuronal lineages are variation hotspots and thus may be more amenable to evolutionary change.

Effects of Single‐ and Mixed‐Species Group Composition on the Flight Initiation Distances of Plains and Grevy's Zebras

AbstractZebras, as prey species, attend to the behavior of nearby conspecifics and heterospecifics when making decisions to flee from predators. Plains zebras (Equus quagga) and Grevy's zebras (E. grevyi) frequently form mixed‐species groups in zones where their ranges overlap in Kenya. Although anecdotal observations suggest that Plains zebras are more flighty around humans than Grevy's zebras are, this has not been empirically confirmed, and relatively little is known about how they may influence each other's flight behavior. We addressed these questions by examining the flight initiation distances (FIDs) of Plains and Grevy's zebras in single‐species and mixed‐species groups from an approaching human. One target individual per group was approached steadily on foot, with start distance, alert distance, and FID recorded from this target. Using start distance and alert distance separately as covariates, 22 Plains zebras in single‐species groups exhibited a significantly longer mean FID than 15 Grevy's zebras in single‐species groups. The FIDs of 7 Plains zebras and 5 Grevy's zebras tested in mixed‐species groups were virtually equivalent and intermediate to those of Plains and Grevy's zebras in single‐species groups, suggesting a bidirectional moderating influence of heterospecifics on risk assessment. This effect was most pronounced for Plains zebras in mixed‐species groups that exhibited an FID that was significantly shorter than that of Plains zebras in single‐species groups. Our findings underscore the importance of recognizing that related equids may be differently impacted by anthropogenic stress.

Reactions of ground-nesting marine birds to human disturbance in the Canadian Arctic

I studied the reactions of five ground-nesting marine bird species (Arctic tern (Sterna paradisaea), Sabine’s gull (Xema sabini), common eider (Somateria mollissima), long-tailed duck (Clangula hyemalis), and Ross’ gull (Rhodostethia rosea)) breeding in the low and high Arctic to disturbance from nearby aircraft as well as avian flight initiation response to humans approaching on foot. All species except nesting long-tailed ducks and common eiders departed their nest when overhead aircraft were within 200 m, with loafing birds often flying off when aircraft were still 1 km away. There was considerable individual and species-specific variation in responses to approaching humans, with some nesting birds not flushing from their nest until touched by a researcher (e.g., waterfowl, 0 m), while others flushed when people were 400 m away (Ross’s gull). Excluding Ross’s gulls, 95% of the individuals of most species did not initiate flight until humans were ≤100 m from the nest, suggesting that this might represent a minimum, suitable “buffer zone” around nesting colonies for nonmotorized human activities.

Electrical Stimulation of Coleopteran Muscle for Initiating Flight

Some researchers have long been interested in reconstructing natural insects into steerable robots or vehicles. However, until recently, these so-called cyborg insects, biobots, or living machines existed only in science fiction. Owing to recent advances in nano/micro manufacturing, data processing, and anatomical and physiological biology, we can now stimulate living insects to induce user-desired motor actions and behaviors. To improve the practicality and applicability of airborne cyborg insects, a reliable and controllable flight initiation protocol is required. This study demonstrates an electrical stimulation protocol that initiates flight in a beetle (Mecynorrhina torquata, Coleoptera). A reliable stimulation protocol was determined by analyzing a pair of dorsal longitudinal muscles (DLMs), flight muscles that oscillate the wings. DLM stimulation has achieved with a high success rate (> 90%), rapid response time (< 1.0 s), and small variation (< 0.33 s; indicating little habituation). Notably, the stimulation of DLMs caused no crucial damage to the free flight ability. In contrast, stimulation of optic lobes, which was earlier demonstrated as a successful flight initiation protocol, destabilized the beetle in flight. Thus, DLM stimulation is a promising secure protocol for inducing flight in cyborg insects or biobots.

Differences in measures of boldness even when underlying behavioral syndromes are present in two populations of the song sparrow (Melospiza melodia)

One commonly studied behavioral syndrome is the correlation between aggression and boldness. Studies in song sparrows (M. melodia) have found greater aggression and boldness in urban populations and a correlation between aggression and boldness in rural populations, but not within urban populations. In previous studies, boldness was measured as flight initiation distance (FID), which may reflect habituation by urban birds to human presence. In this study, we measured boldness using playbacks of heterospecific alarm calls and investigated whether higher boldness is a general trait of urban birds and whether the same pattern of correlations between aggression and boldness would be seen. We conducted trials involving FID, alarm call playbacks and conspecific song playbacks on 25 birds from both an urban and a rural site. The results showed that urban birds were bolder, as measured by FID and response to alarm calls. Boldness and aggression were correlated in rural birds with each method of measuring boldness but were correlated in urban birds only when using alarm call playbacks. Our results suggest that a behavioral syndrome exists in both urban and rural populations but that urban birds are able to decrease their response to human disturbance.

“Shortest-distance” method is more accurate than conventional method in estimating flight initiation distances for close, perched birds

The conventional method to determine avian flight initiation distance (the distance at which birds exposed to an approaching human activity initiate escape behavior) overestimates this distance for perched birds because it uses the distance between the bird and the ground at the person’s feet rather than the distance between the bird and the part of the person’s body closest to the bird. Here, we introduce an alternative “shortest-distance” method that more accurately estimates flight initiation distance, especially for close, perched birds.

When to flee? The economics of sneakers facing territorial aggression

In species with alternative reproductive tactics, territorial males (guarders) are usually vigilant against sneakers, and aggressively attempt to eliminate them, imposing serious costs (injuries, sometimes death). Here I examined how sneakers escape from territorial attack in the triplefin blenny, Enneapterygius etheostoma, in the field, with the help of economic flight theory developed for predator–prey interactions. Sneakers hide around spawning sites for sneaking, but they are often detected and attacked by territorial males. Fleeing soon after the initiation of attack could reduce the risk of injuries. However, fleeing may be the wrong decision, resulting in a loss of benefit that could have been obtained by not fleeing, because of uncertainty about whether the sneaker is targeted. As the guarder–sneaker distance decreases, the target would become clear, and uncertainty is reduced accordingly. Therefore, it is predicted that flight initiation distance (FID, the predator–prey distance when escape begins) is determined by the cost–benefit balance. Two types of territorial aggression were identified: the ‘direct approach’, where the territorial male directly approaches a given sneaker, and the ‘reoriented approach’, where the territorial male turns to reorient and approaches it following an attack against the first target. A field study showed that sneakers fled earlier in the reoriented approach than in the direct approach. Model selection showed that FID in the reoriented approach was predicted by the guarder–sneaker distance at attack initiation (starting distance) alone, whereas FID in the direct approach was predicted by starting distance, the interaction between the approach speed of territorial males and the duration for which the sneakers monitored them. These results suggest that sneakers adjust flight decision rules to attack episodes, i.e. the economic decision in the direct approach, but the flush early decision in the reoriented approach. This study provides a novel example of adaptation in sneakers.

Locomotor behavior of Sitophilus zeamais populations under sublethal ozone exposure

Insects exhibit diverse behavioral responses under insecticide exposure. However, such responses have been neglected in toxicological studies. The purpose of this work was to evaluate the influence of sublethal concentrations of ozone on the locomotor behavior of populations of the maize weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). Additionally, respiration rate and body mass were also evaluated. The behavioral characteristics evaluated were distance traveled, resting time, and walking velocity of males and females, along with flight initiation for non-sexed insects. Ozone concentrations of 0, 30, 40, 50, and 60 ppm were established for the Amambay population and ozone concentrations of 0, 50, 75, 100, 125, and 150 ppm for the Sao Joao population of S. zeamais. The walking activity of the Amambay insect population decreased with increasing ozone concentration. In contrast, the walking activity of the Sao Joao population did not vary with ozone concentration. At least one of the walking characteristics is correlated with the respiration rate and body mass, indicating an association of increased respiration rate and body mass with reduced walking activity. In general, the behavioral response to ozone was population dependent. The reduction in walking activity of the S. zeamais populations under sublethal ozone exposure might limit the insect’s ability to escape its effects. These results implicate in a low risk of resistance evolution in a short term, indicating that ozone is a potential option to control pest insects of stored products.

The effects of temperature, relative humidity, light, and resource quality on flight initiation in the red flour beetle, Tribolium castaneum.

We investigated the environmental conditions that induce a flight response in the red flour beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae), including resource quality, temperature, relative humidity, and light. Over 72-h trial periods, we observed the proportion of individuals emigrating by flight to range from 0.0 in extreme heat or cold to 0.82 with starvation. Resource quality, presence of a light source, and temperature all directly influenced the initiation of the flight response. We did not detect any effect of relative humidity or sudden change in temperature on the incidence of flight. We discuss our findings in the context of Tribolium ecology and evolution.

Opposite companion effect on flight initiation distance in sympatric species: plateau pika (Ochotona curzoniae) and White-rumped Snowfinch (Onychostruthus taczanowskii)

There are many factors influencing prey’s risk perception and escape decision during predator–prey encounters. The distance at which animals move away from perceived danger (often quantified as flight initiation distance or FID) has been used by behavioral ecologists to understand the economics of antipredator behavior. Using general linear models, we investigated escape decision-making processes in plateau pika (Ochotona curzoniae (Hodgson, 1858)) and White-rumped Snowfinch (Onychostruthus taczanowskii (Prjevalsky, 1876), formerly known as Montifringilla taczanowskii Przewalski, 1876) together and we found that (i) there are significant positive correlations between starting distance and FID in both species; (ii) pika escapes at a longer distance from an approaching intruder when it is far from its burrow; (iii) foraging animals tolerate closer distances than watching ones, both in pikas and in Snowfinches; (iv) conspecifics seem to have no effect on pikas’ escaping behavior, while the appearance of Snowfinches dramatically decreases the FID of pikas. On the contrary, conspecifics significantly decrease the FID of Snowfinches, while the presence of pikas has no effects. These findings provide new evidence, which are consistent with optimal escape theory. These novel results in multispecies interactions prompt us to pay attention to the potential relationship between pikas and Snowfinches, as well as the “bird–pika in one hole” phenomenon.

Database of Bird Flight Initiation Distances to Assist in Estimating Effects from Human Disturbance and Delineating Buffer Areas

AbstractU.S. Fish and Wildlife Service biologists determine effects from disturbance to threatened and endangered bird species, and staffs of federal and state agencies estimate these effects when delineating protective buffers around habitat of bird species of concern on land management areas. These efforts can be informed by the distances at which human activities cause birds to react or move away. To that end, here we present a database of published alert distances (distances at which birds exposed to an approaching human activity exhibit alert behavior), flight initiation distances (distances at which birds exposed to an approaching human activity initiate escape behavior), and minimum approach distances (distances at which humans should be separated from wildlife). The database distinguishes between nesting and nonnesting situations. The nesting database includes 578 alert distances and 2,177 flight initiation distances from 45 studies representing 11 orders, 27 families, and 49 species of birds. The nonnesting database comprises 1,419 alert distances and 34,775 flight initiation distances from 50 studies representing 19 orders, 89 families, and 650 species.

Spearfishing-induced behavioral changes of an unharvested species inside and outside a marine protected area.

By prohibiting fishing, marine protected areas (MPAs) provide a refuge for harvested species. Humans are often perceived as predators by prey and therefore respond fearfully to humans. Thus, fish responses to humans inside and outside of an MPA can provide insights into their perception of humans as a predatory threat. Previous studies have found differences in the distance that harvested species of fish initiate flight (flight initiation distance—FID) from humans inside and outside an MPA, but less is known about unharvested species. We focused on whether the lined bristletooth Ctenochaetus striatus, an unharvested surgeonfish, can discriminate between a snorkeler and a snorkeler with a spear gun inside and outside of a no-take MPA in Mo’orea, French Polynesia. Additionally, we incorporated starting distance (the distance between the person and prey at the start of an experimental approach), a variable that has been found to be important in assessing prey escape decisions in terrestrial species, but that has not been extensively studied in aquatic systems. Lined bristletooth FID was significantly greater in the presence of a spear gun and varied depending on if the spear gun encounter was inside or outside of the MPA. These results imply a degree of sophistication of fish antipredator behavior, generate questions as to how a nontargeted species of fish could acquire fear of humans, and demonstrate that behavioral surveys can provide insights about antipredator behavior.

Evaluation of the Effects of Light Intensity and Time Interval After the Start of Scotophase on the Female Flight Propensity of Asian Gypsy Moth (Lepidoptera: Erebidae).

Asian gypsy moth, Lymantria dispar L. (Lepidoptera: Erebidae), females are capable of flight, but little is known about what causes the variation in flight propensity that has been observed. The female flight propensity and capability of Asian gypsy moth from seven geographic populations (three from China, two from Russia, one from Japan, and one from Korea) were compared under all combinations of three light intensities (0.05, 0.10, and 0.40 lux) and during three time intervals after the start of scotophase. A total of 567 females were flight tested. Female flight propensity, time to initiate walking, fanning, and flying, and duration of fanning differed significantly among geographic populations. Females were less likely to voluntarily fly during the 0-1-h time interval after the start of scotophase than during the later time intervals (1-2 and 2-3 h), suggesting that the light intensity cue has to occur at the correct time after the expected start of scotophase for flight initiation. Light intensity did not significantly affect the proportion of females that voluntarily flew, but did impact the timing of the walking and fanning preflight behaviors. The interaction between light intensity and time interval after the start of scotophase had a significant effect on the proportion of females that fanned. The proportion of females with sustained flight capability varied among the populations evaluated. These results may aid in determining the risk of Asian gypsy moth dispersal, but further work is needed to assess other factors that play a role in flight propensity.

Morphological and physiological determinants of local adaptation to climate in Rocky Mountain butterflies.

Flight is a central determinant of fitness in butterflies and other insects, but it is restricted to a limited range of body temperatures. To achieve these body temperatures, butterflies use a combination of morphological, behavioural and physiological mechanisms. Here, we used common garden (without direct solar radiation) and reciprocal transplant (full solar radiation) experiments in the field to determine the thermal sensitivity of flight initiation for two species of Colias butterflies along an elevation gradient in the southwestern Rocky Mountains. The mean body temperature for flight initiation in the field was lower (24-26°C) than indicated by previous studies (28-30°C) in these species. There were small but significant differences in thermal sensitivity of flight initiation between species; high-elevation Colias meadii initiated flight at a lower mean body temperature than lower-elevation Colias eriphyle. Morphological differences (in wing melanin and thoracic setae) drive body temperature differences between species and contributed strongly to differences in the time and probability of flight and air temperatures at flight initiation. Our results suggest that differences both in thermal sensitivity (15% contribution) and in morphology (85% contribution) contribute to the differences in flight initiation between the two species in the field. Understanding these differences, which influence flight performance and fitness, aids in forecasting responses to climate change.

Escape behaviour in the leopard lizard (Gambelia wislizenii): effects of starting distance and sex

Predation risk influences decision making, escape behaviour, and resource use. Risk assessment and behavioural responses to predation can depend on demographic and environmental factors. We studied the escape behaviour of the long-nosed leopard lizard (Gambelia wislizenii) when approached by a human predator (= “simulated predator”), analysing flight initiation distance (FID) and flight distance (FD) relative to demographic and environmental variables. Starting distance (SD) of the simulated predator and orientation of prey lizards relative to the simulated predator influenced FID, but body size of the prey lizard did not. Sex interacted with SD to affect FID. Females lengthened their FIDs as SD increased, while male FID was unrelated to SD. Flight distance increased with increasing SD.Gambelia wislizenii’s ecological role as an ambush predator may explain their escape behaviour; reproductive status potentially affected the interaction between sex and SD.