Convergent patterns of long-distance nocturnal migration in noctuid moths and passerine birds

Vast numbers of insects and passerines achieve long-distance migrations between summer and winter locations by undertaking high-altitude nocturnal flights. Insects such as noctuid moths fly relatively slowly in relation to the surrounding air, with airspeeds approximately one-third of that of passerines. Thus, it has been widely assumed that windborne insect migrants will have comparatively little control over their migration speed and direction compared with migrant birds. We used radar to carry out the first comparative analyses of the flight behaviour and migratory strategies of insects and birds under nearly equivalent natural conditions. Contrary to expectations, noctuid moths attained almost identical ground speeds and travel directions compared with passerines, despite their very different flight powers and sensory capacities. Moths achieved fast travel speeds in seasonally appropriate migration directions by exploiting favourably directed winds and selecting flight altitudes that coincided with the fastest air streams. By contrast, passerines were less selective of wind conditions, relying on self-powered flight in their seasonally preferred direction, often with little or no tailwind assistance. Our results demonstrate that noctuid moths and passerines show contrasting risk-prone and risk-averse migratory strategies in relation to wind. Comparative studies of the flight behaviours of distantly related taxa are critically important for understanding the evolution of animal migration strategies.     

The Sickle-cell and Altitude

High altitude seemed to be responsible for seven recent cases of sickling crisis. People with sickle-cell trait are at risk if they fly in unpressurized aircraft, which are used for many local air services. Those with sickle-cell haemoglobin C disease should avoid air travel even in pressurized aircraft. Possibly as a result of “autosplenectomy,” patients with sickle-cell anaemia seem to be able to fly in pressurized aircraft with little risk. All passengers and aircrew who might have some form of sickle-cell disease should be screened before flight.     

Barometer logging reveals new dimensions of individual songbird migration

Recent advances in tracking technology are based on the use of miniature sensors for recording new aspects of individual migratory behaviour. In this study, we have used activity data loggers with barometric and temperature sensors to record the flight altitudes as well as ground elevations during stationary periods of migratory songbirds. We tracked one individual of red‐backed shrike and one great reed warbler along their autumn migration from Europe to Africa. Both individuals performed their migration stepwise in travel segments and climbed most metres during the passage across the Mediterranean Sea and the Sahara Desert and least metres during the first flight segment in Europe. The great reed warbler reached its highest flight altitude of 3950 m a.s.l. during the travel segment from Europe to west Africa, while the red‐backed shrike reached 3650 m a.s.l as maximum flight altitude during its travel segment from Sahel to southern Africa. Both individuals used both lowlands and highlands for resting periods along their migrations. Furthermore, temperature decreased with increasing altitude during migratory flights for both individuals, highlighting the potential to determine flight duration from temperature measurements. Finally, we discuss how barometric data could be used to investigate birds’ responses to changes in air pressure as a cue for departures on migratory flights. This new technique, i.e. using a miniature data logger with barometric pressure sensor to estimate flight altitudes and ground elevations, will open up new avenues for research and importantly advance our understanding on how small birds behave during migratory flights.     

Flight by night or day? Optimal daily timing of bird migration

Many migratory bird species fly mainly during the night (nocturnal migrants), others during daytime (diurnal migrants) and still others during both night and day. Need to forage during the day, atmospheric structure, predator avoidance and orientation conditions have been proposed as explanations for the widespread occurrence of nocturnal migration. However, the general principles that determine the basic nocturnal-diurnal variation in flight habits are poorly known. In the present study optimal timing of migratory flights, giving the minimum total duration of the migratory journey, is evaluated in a schematic way in relation to ecological conditions for energy gain in foraging and for energy costs in flight. There exists a strong and fundamental advantage of flying by night because foraging time is maximized and energy deposition can take place on days immediately after and prior to the nocturnal flights. The increase in migration speed by nocturnal compared with diurnal migration will be largest for birds with low flight costs and high energy deposition rates. Diurnal migration will be optimal if it is associated with efficient energy gain immediately after a migratory flight because suitable stopover/foraging places have been located during the flight or if energy losses during flight are substantially reduced by thermal soaring and/or by fly-and-forage migration. A strategy of combined diurnal and nocturnal migration may be optimal when birds migrate across regions with relatively poor conditions for energy deposition (not only severe but also soft barriers). Predictions about variable timing of migratory flights depending on changing foraging and environmental conditions along the migration route may be tested for individual birds by analysing satellite tracking results with respect to daily travel routines in different regions. Documenting and understanding the adaptive variability in daily travel schedules among migrating animals constitute a fascinating challenge for future research.     

Travel patterns and risk behaviour of HIV-positive people travelling internationally

Background

International travel is associated with an increased risk of enteric, vector-borne, sexually transmitted and blood-borne infections. These risks are even higher among immunocompromised people, such as those with HIV infection. We conducted a study to determine HIV-positive people''s travel patterns and risk behaviours while abroad.

Methods

We conducted an anonymous survey of HIV-positive people attending an HIV clinic in a tertiary care hospital in Toronto about their travel activities and pretravel precautions as well as their burden of illness and risk exposure during travel. We compared the characteristics of respondents who had travelled outside Canada and the United States (international travellers) with those of respondents who had not travelled internationally.

Results

Of 290 HIV-positive people who participated in the study, 133 (45.9%) indicated that they had travelled internationally in the 5 years before the survey. These people were predominantly men (93.2%) and well educated (60.0% had a university level education), and they had travelled mostly for personal reasons (89.5%) on trips that lasted 3.6 weeks on average. Only 58 (43.6%) sought health advice before travelling, and only 17 (12.8%) sought advice from a travel clinic. Five (3.8%) had received live vaccines before travel, and 9 (6.8%) had taken malaria chemoprophylaxis. Of the 119 international travellers who were taking antiretroviral therapy; 35 (29.4%) reported either discontinuing their medications or being poorly compliant with the therapy while travelling. Thirty-one (23.3%) of the 133 international travellers reported having had casual sexual activity with new partners while travelling, and only 18 (58.1%) of them reported always using a condom. Twenty-one (15.8%) of the 133 reported having had risky exposure to sharps. Twenty-four (18.0%) said they had become ill enough while travelling to require medical attention.

Interpretation

Only one-fifth of HIV-positive people surveyed who travelled internationally sought advice from a health professional before their trip. Their travel was associated with poor adherence to antiretroviral therapy, risky sexual practices and risky exposure to sharps.The incidence of infectious diseases in returning international travellers continues to increase.¹ Overseas travel is especially associated with exposure to enteric and vector-borne pathogens, and travellers who engage in risky behaviours (e.g., unsafe sex and exposure to sharps) are at increased risk of blood- and body fluid-borne infections.^1,2,3,4,5 Lifestyle factors and underlying health status influence the predisposition to and the severity of infections in travellers. HIV-positive travellers may be particularly susceptible to acquiring infections.^6,7 In addition, they have to take into consideration issues related to their complex medication regimens and access to appropriate medical care while abroad.^8,9To date, there have been few comprehensive studies of HIV-positive people''s travel practices, risk behaviours and complications incurred by travelling. The aim of our study was to profile HIV-positive people who travelled internationally with respect to their demographic characteristics, their preparations before travel, their travel practices, their risk behaviour and exposure to blood and body fluids during travel, and medical help required while abroad.     

Prediction of hypoxaemia at high altitude in children with cystic fibrosis.

OBJECTIVE--To assess the usefulness of a hypoxic challenge in a laboratory at sea level in predicting acute desaturation at altitude in children with lung disease. DESIGN--Comparison of responses to hypoxic challenge in different settings. SUBJECTS--22 children (12 boys) aged 11 to 16 years with cystic fibrosis in whom the mean forced expiratory volume in one second was 64% (range 24-100%). SETTING--Lung function laboratory, the Alps, and aboard commercial jet aircraft. MAIN OUTCOME MEASURES--Spirometric lung function at sea level and finger probe oximetry with air and 15% oxygen. Oximetry during high altitude flight and on a mountain at altitude of 1800 m. RESULTS--Significant desaturation (range 0 to 12%) occurred with all hypoxic challenges (P < 0.002). The best predictor of hypoxic response from a single reading was the laboratory test (r2 = 76% for flight and r2 = 47% for mountain altitude), but the mean errors of prediction were not clinically significantly different. In six children who showed the greatest desaturation the laboratory test overestimated desaturation, but other predictors underestimated desaturation in three by up to 5%. CONCLUSIONS--The laboratory hypoxic challenge directly predicted the worst case of desaturation during flight and at equivalent high altitude. Spirometry and baseline oxygen saturations may underestimate individual hypoxic response. The test may have wider applications to other patients with stable chronic lung diseases, particularly in determining who needs supplementary oxygen during air travel and who should be advised against holidays at high altitude.     

Ethylene Is Responsible for a Disturbed Development of Plant Reproductive System under Conditions of Space Flight

The development of reproductive organs was studied on three dwarf cultivars of wheat Triticum aestivum and the fast-cycling Brassica rapa plants, grown under earth control conditions, during the space flight in the Mir orbital station, and in a earth experiment that simulated growth conditions during the space flight, including an elevated content of ethylene in the air (1 mg/m³ on average). We found that the embryological characteristics of the plants were not affected by space flight conditions. The elevated ethylene content in air resulted in some changes in the morphometric characteristics of inflorescences and a greater frequency of sterility similar under conditions of space flight and control earth experiment. We conclude that the abnormalities and modifications in the development of reproductive organs, induced by space flight conditions, were caused by a secondary factor, an elevated ethylene content in the cabin air, rather than by microgravity.     

La consultation médicale avant un départ en pays tropical

This article specifies the key factors that must be taken into consideration during medical examinations before travel to tropical countries. The factors include vaccinations and vaccine contraindications, antimalarial prophylaxis and drug interactions, diarrhoea prevention, special precautions for certain travellers (children, pregnant women, the elderly, and immunosuppressed persons), and general prophylaxis.     

Egomotion estimation with optic flow and air velocity sensors

We develop a method that allows a flyer to estimate its own motion (egomotion), the wind velocity, ground slope, and flight height using only inputs from onboard optic flow and air velocity sensors. Our artificial algorithm demonstrates how it could be possible for flying insects to determine their absolute egomotion using their available sensors, namely their eyes and wind sensitive hairs and antennae. Although many behaviors can be performed by only knowing the direction of travel, behavioral experiments indicate that odor tracking insects are able to estimate the wind direction and control their absolute egomotion (i.e., groundspeed). The egomotion estimation method that we have developed, which we call the opto-aeronautic algorithm, is tested in a variety of wind and ground slope conditions using a video recorded flight of a moth tracking a pheromone plume. Over all test cases that we examined, the algorithm achieved a mean absolute error in height of 7% or less. Furthermore, our algorithm is suitable for the navigation of aerial vehicles in environments where signals from the Global Positioning System are unavailable.     

Regional and seasonal flight speeds of soaring migrants and the role of weather conditions at hourly and daily scales

Given that soaring birds travel faster with supportive winds or in good thermal soaring conditions, we expect weather conditions en route of migration to explain commonly observed regional and seasonal patterns in the performance of soaring migrants. We used GPS‐loggers to track 13 honey buzzards and four Montagu's harriers for two to six migrations each. We determined how tailwinds, crosswinds, boundary layer height (a proxy for thermal convection) and precipitation affected hourly speeds, daily distances and daily mean speeds with linear regression models. Honey buzzards mostly travel by soaring while Montagu's harriers supplement soaring with flapping. Therefore, we expect that performance of harriers will be less affected by weather than for buzzards. Weather conditions explained between 30 and 50% of variation in migration performance of both species. Tailwind had the largest effect on hourly speeds, daily mean speeds and daily travel distances. Honey buzzards travelled significantly faster and farther, and Montagu's harriers non‐significantly faster, under better convective conditions. Honey buzzards travelled at slower speeds and shorter distances in crosswinds, whereas harriers maintained high speeds in crosswinds. Weather conditions varied between regions and seasons, and this variation accounted for nearly all regional and seasonal variation in flight performance. Hourly performance was higher than predicted at times when we suspect birds had switched to intermittent or continuous flapping flight, for example during sea‐crossings. The daily travel distance of Montagu's harriers was determined to a significant extent by their daily travel time, which differed between regions, possibly also due to weather conditions. We conclude with the implications of our work for studies on migration phenology and we suggest an important role for high‐resolution telemetry in understanding migratory behavior across entire migratory journeys.     

The paradox of extreme high-altitude migration in bar-headed geese Anser indicus

Bar-headed geese are renowned for migratory flights at extremely high altitudes over the world''s tallest mountains, the Himalayas, where partial pressure of oxygen is dramatically reduced while flight costs, in terms of rate of oxygen consumption, are greatly increased. Such a mismatch is paradoxical, and it is not clear why geese might fly higher than is absolutely necessary. In addition, direct empirical measurements of high-altitude flight are lacking. We test whether migrating bar-headed geese actually minimize flight altitude and make use of favourable winds to reduce flight costs. By tracking 91 geese, we show that these birds typically travel through the valleys of the Himalayas and not over the summits. We report maximum flight altitudes of 7290 m and 6540 m for southbound and northbound geese, respectively, but with 95 per cent of locations received from less than 5489 m. Geese travelled along a route that was 112 km longer than the great circle (shortest distance) route, with transit ground speeds suggesting that they rarely profited from tailwinds. Bar-headed geese from these eastern populations generally travel only as high as the terrain beneath them dictates and rarely in profitable winds. Nevertheless, their migration represents an enormous challenge in conditions where humans and other mammals are only able to operate at levels well below their sea-level maxima.     

Preventing deaths from malaria.

To reduce the number of avoidable deaths from malaria in Britain the following five points are recommended. Parliament should pass a Malaria Prevention Act that compels travel agents and airlines to give written and verbal advice on prevention and diagnosis of malaria to people travelling to countries where the disease occurs. To improve diagnostic and therapeutic efficiency for all diseases the Department of Health and Social Security should prepare a procedure manual for the NHS that gives guidance for doctors and other medical staff. Avoidable deaths from all diseases should be the subject of open inquiries at district medical committees, with recorded evidence. Failure to perform diagnostic tests such as blood films for malaria in cases of sickness in people returning from the tropics should automatically be considered negligent. Compensation should be offered by the State to the next of kin of people who have died because of medical negligence from malaria or other diseases.     

Preconception care: a parenting protocol: a moral inquiry into the responsibilities of future parents towards their future children

In the Netherlands fertility doctors increasingly formulate protocols, which oblige patients to quit their unhealthy lifestyle before they are admitted to IVF procedures. We argue that moral arguments could justify parenting protocols that concern all future parents. In the first part we argue that want-to-be parents have moral responsibilities towards their future children to prevent them from harm by diminishing or eliminating risk factors before as well as during the pregnancy. This is because of the future children's potential to become of a certain type, more specifically: a person that will be the want-to-be parents' child. Want-to-be parents intend to become pregnant and therefore have an additional moral reason to diminish the risks. Also, people who become pregnant unintentionally have the responsibility to prevent their children from harm, unless they become pregnant due to contraception failure. All people not wanting to become pregnant should use contraception methods carefully. In the second part of this paper we translate the want-to-be parents' responsibilities into practice. We distinguish four determinants of risk factors: modifiability, chance, severity and effort. We examine some evidence-based risk factors based on these variables and deduce levels of responsibility. In conclusion, formulating informal requirements for want-to-be parents is morally required and therefore also for want-to-be parents in need of medical assistance. The protocols developed by fertility doctors in the Netherlands could be seen as the precursor for a general, informal Parenting Protocol that could be developed on the basis of an extended and thoroughly debated risk-responsibility analysis.     

Predictive adaptive responses: Condition-dependent impact of adult nutrition and flight in the tropical butterfly Bicyclus anynana

The experience of environmental stress during development can substantially affect an organism's life history. These effects are often mainly negative, but a growing number of studies suggest that under certain environmental conditions early experience of such stress may yield individuals that are less sensitive to environmental stress later on in life. We used the butterfly Bicyclus anynana to study the effects of limited larval and adult food and forced flight on individual performance measured as reproduction and adult life span. Larvae exposed to food stress showed longer development and produced smaller adults. Thus, they were not able to fully compensate for the food deprivation during development. Females that experienced food stress during development did not increase tolerance for adult food limitation. However, females exposed to food stress during development coped better with forced flight compared with the control group. The apparent absence of costs of flight in poor-quality females may be a by-product of an altered body allocation, as females experiencing both food stress treatments had increased thorax ratios, compared with controls, and increased flight performances. The results reveal an important plasticity component to variation in flight performance and suggest that the cost of flight depends on an individual's internal condition.     

Aeromedical transport: its hidden problems.

Air transport can move patients safely and rapidly over long distances. However, changes in altitude can have disastrous effects because diminished ambient air pressure may allow gases in closed spaces and tissues to expand rapidly. Even pressurized commercial aircraft do not maintain sea-level pressure: cabin pressures equal to those at yp to 8000 ft may be experienced, diminishing oxygen tension in proportion. Air transport is absolutely contraindicated for patients with untreated pneumothorax, gas gangrene, or air trapped in the cranium and those who have recently undergone abdominal surgery. Special considerations including a planned low-altitude flight are warrented for patients who are anemic, in respiratory or cardiac distress, or immobilized in casts, or who have been engaged in underwater diving immediately before the flight.     

How Cheap Is Soaring Flight in Raptors? A Preliminary Investigation in Freely-Flying Vultures

Measuring the costs of soaring, gliding and flapping flight in raptors is challenging, but essential for understanding their ecology. Among raptors, vultures are scavengers that have evolved highly efficient soaring-gliding flight techniques to minimize energy costs to find unpredictable food resources. Using electrocardiogram, GPS and accelerometer bio-loggers, we report the heart rate (HR) of captive griffon vultures (Gyps fulvus and G. himalayensis) trained for freely-flying. HR increased three-fold at take-off (characterized by prolonged flapping flight) and landing (>300 beats-per-minute, (bpm)) compared to baseline levels (80–100 bpm). However, within 10 minutes after the initial flapping phase, HR in soaring/gliding flight dropped to values similar to baseline levels, i.e. slightly lower than theoretically expected. However, the extremely rapid decrease in HR was unexpected, when compared with other marine gliders, such as albatrosses. Weather conditions influenced flight performance and HR was noticeably higher during cloudy compared to sunny conditions when prolonged soaring flight is made easier by thermal ascending air currents. Soaring as a cheap locomotory mode is a crucial adaptation for vultures who spend so long on the wing for wide-ranging movements to find food.     

Flying Drosophila orient to sky polarization

Insects maintain a constant bearing across a wide range of spatial scales. Monarch butterflies and locusts traverse continents [1, 2], and foraging bees and ants travel hundreds of meters to return to their nests [1, 3, 4], whereas many other insects fly straight for only a few centimeters before changing direction. Despite this variation in spatial scale, the brain region thought to underlie long-distance navigation is remarkably conserved [5, 6], suggesting that the use of a celestial compass is a general and perhaps ancient capability of insects. Laboratory studies of Drosophila have identified a local search mode in which short, straight segments are interspersed with rapid turns [7, 8]. However, this flight mode is inconsistent with measured gene flow between geographically separated populations [9-11], and individual Drosophila can travel 10 km across desert terrain in a single night [9, 12, 13]-a feat that would be impossible without prolonged periods of straight flight. To directly examine orientation behavior under outdoor conditions, we built a portable flight arena in which a fly viewed the natural sky through a liquid crystal device that could experimentally rotate the polarization angle. Our findings indicate that Drosophila actively orient using the sky's natural polarization pattern.     

Air travel across four time zones in college swimmers

Eighteen female and 22 male college swimmers were flown across four time zones in east-to-west (E-W) and west-to-east (W-E) directions. A pre- and postflight paced swim of 182.9 m at an intensity equal to 90% of the swimmers' maximal velocity was completed, and salivary cortisol, heart rate (HR), and rated perceived exertion were measured. Blood pressure, HR, muscle soreness, and mood were also assessed at rest on the day before and on the day after travel. Because training volumes for both females and males were greater (P less than 0.001) in the week before W-E than E-W travel, the W-E and E-W data were analyzed separately. Two-way repeated-measures analyses of variance revealed that pre- and postexercise cortisol decreased after E-W travel and increased after W-E travel in comparison to preflight values. Resting and exercise HR responses to air travel were small in magnitude, and their significance depended on the direction of travel. Effort sense was not altered by air travel, but significant (P less than 0.001) improvements in mood and reductions in muscle soreness were observed after E-W and W-E travel for both genders. It was concluded that 1) female and male college swimmers have similar responses to air travel and 2) air travel across four time zones during heavy swim training does not have negative physiological, perceptual, or affective consequences.     

Collision avoidance in commercial aircraft Free Flight via neural networks and non-linear programming

In recent years there has been a great effort to convert the existing Air Traffic Control system into a novel system known as Free Flight. Free Flight is based on the concept that increasing international airspace capacity will grant more freedom to individual pilots during the enroute flight phase, thereby giving them the opportunity to alter flight paths in real time. Under the current system, pilots must request, then receive permission from air traffic controllers to alter flight paths. Understandably the new system allows pilots to gain the upper hand in air traffic. At the same time, however, this freedom increase pilot responsibility. Pilots face a new challenge in avoiding the traffic shares congested air space. In order to ensure safety, an accurate system, able to predict and prevent conflict among aircraft is essential. There are certain flight maneuvers that exist in order to prevent flight disturbances or collision and these are graded in the following categories: vertical, lateral and airspeed. This work focuses on airspeed maneuvers and tries to introduce a new idea for the control of Free Flight, in three dimensions, using neural networks trained with examples prepared through non-linear programming.     

Meteorological and environmental variables affect flight behaviour and decision‐making of an obligate soaring bird,the California Condor Gymnogyps californianus

The movements of animals are limited by evolutionary constraints and ecological processes and are strongly influenced by the medium through which they travel. For flying animals, variation in atmospheric conditions is critically influential in movement. Obligate soaring birds depend on external sources of updraft more than do other flying species, as without that updraft they are unable to sustain flight for extended periods. These species are therefore good models for understanding how the environment can influence decisions about movement. We used meteorological and topographic variables to understand the environmental influences on the decision to engage in flight by obligate soaring and critically endangered California Condors Gymnogyps californianus. Condors were more likely to fly, soared at higher altitudes and flew over smoother terrain when weather conditions promoted either thermal or orographic updrafts, for example when turbulence and solar radiation were higher and when winds from the east and north were stronger. However, increased atmospheric stability, which is inconsistent with thermal development but may be associated with orographic updrafts, was correlated with a somewhat higher probability of being in flight at lower altitudes and over rougher terrain. The close and previously undescribed linkages between Condor flight and conditions that support development of thermal and orographic updrafts provide important insight into the behaviour of obligate soaring birds and into the environmental parameters that may define the currently expanding distribution of Condors within and outside the state of California.