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Wikelski, M.

Publications and source records attributed to Wikelski, M..

At least 19 recordsLinked to original sources
bioRxiv2026

Fine-scale flight behaviour reveals eagles' response to different uplift sources and highlights observational gaps in high-resolution weather models.

Understanding how animals respond to their physical environment requires environmental observations at the scale at which behavioural decisions are made. For soaring birds, the coarse resolution of weather products has long hindered the analysis of their behavioural response to fine-scale atmospheric dynamics, forcing uplift sources to be inferred largely from behaviour itself. Here, we combined high-resolution movement data from 24 golden eagles with the kilometre-scale COSMO weather model. We first classified thermal, orographic, and gravity-wave uplifts using independent atmospheric predictors and then quantified the birds' use of each uplift type and their fine-scale behavioural responses. Eagles relied predominantly on thermals, but opportunistically adjusted their use of uplift sources seasonally. The birds' flight behaviour could not reliably indicate which uplift type was primarily used, and thus suggests that both atmospheric processes and behavioural responses are better described as continua than discrete categories. Finally, we compared vertical wind velocities derived from eagles soaring behaviour with those modelled by the COSMO weather model, showing that most of the thermals exploited by eagles remain unresolved at kilometre-scale model resolution. Our results demonstrate how high-resolution weather models provide new insights into bird movement decisions, while also highlighting the potential of soaring birds as biologically embedded atmospheric sensors that could help closing the resolution gap in atmospheric models.

ecology↗
bioRxiv2026

Rapid population decline of Egyptian fruit bats on Cyprus

Preventing extirpations requires timely detection of rapid declines and immediate conservation response. Egyptian fruit bats (Rousettus aegyptiacus) are globally listed as Least Concern, but their genetically isolated population in Cyprus is Critically Endangered. We document a severe ongoing decline of the Cypriot R. aegyptiacus population observed during standardized counts at major roost sites. April 2024 counts at four principal roosts recorded 4633 bats. Surveys in December 2025 documented 554 individuals across the same sites. April 2026 counts revealed a 90.1% decline since April 2024. Additionally, we found numerous dead bats at three roosts, and residents across the island reported dead bats, suggesting an acute mortality event beginning in early 2025. The cause remains unknown. Given the magnitude and pace of decline, this population potentially faces imminent extirpation. We recommend immediate action to protect roosting and foraging habitat, along with coordinated diagnostics, expedited research permits, standardized monitoring, and technical collaboration to identify and mitigate underlying causes of high mortality.

ecology↗
bioRxiv2026

Early avoidance of human-dominated landscapes by juvenile Alpine golden eagles

O_LIThe expanding human footprint drives profound transformations in species, including not only morphological trait loss but also behavioural trait extinction. In contrast to behavioural trait extinction, which entails a reduction in genetic variability, behavioural plasticity maintains behavioural trait diversity and the associated genetic variability required for evolutionary adaptation. Yet, while behavioural plasticity shaping non-human capacity to coexist with humans has evolved under past, human-modified, environmental conditions, few studies have examined whether species retain a level of behavioural plasticity after past interactions with humans. C_LIO_LIUsing data from 64 juveniles golden eagles (Aquila chrysaetos) from a population demographically recovering after centuries of persecution, yet still restricted to less human-dominated alpine massifs, we tested whether human avoidance is innate or learned through experience during dispersal or parental influences during the pre-dispersal period. We performed a Principal Component Analysis (PCA) on landscape features used during the pre-dispersal and the first fifteen weeks of the dispersal phase, and used Mahalanobis distance as an indicator for quantifying changes in individual spatial behaviour over time. C_LIO_LIThe lower frequency of use of human-dominated landscape features, compared with the more sparsely populated mid- and high-elevation landscape features, resulted from individuals consistent use of similar landscape features across the pre-dispersal and dispersal periods. Avoidance of humans was therefore better explained by a learning or imprinting process prior to dispersal, which predisposed individuals to use landscape features similar to those experienced during pre-dispersal, rather than by learning during dispersal, or by an innate avoidance. C_LIO_LIImprinting on natal habitat features corroborates the observed limited range expansion of the alpine population beyond the massif borders. Differences among European populations in range recolonisation suggest contrasting histories of persecution, which may have left varying degrees of behavioural plasticity across populations. C_LIO_LIAs a guide for future conservation priorities, these findings underscore the need to reconstruct past conditions and/or to document contemporary animal behaviour in order to build a library of behaviours that can be used in the future to track behavioural changes. C_LI

animal behavior and cognition↗
bioRxiv2025

Fine-scale animal proximity detection and localization via multi-sensor biologgers

O_LIAccurately quantifying spatial interactions is central to understanding social behavior, information flow, predator-prey dynamics, and disease transmission. Proximity loggers that record received signal strength indicator (RSSI) offer a promising approach for estimating pairwise distances, particularly in environments where GPS is unavailable or imprecise. However, RSSI is often dismissed as too noisy for fine-scale inference, with performance that depends on environmental conditions, tag orientation, and between-device variability. Incorporating additional tag-measured data may improve RSSI performance and enable its use as a continuous measure of distance in variable environments. C_LIO_LIHere, we assess the utility of continuous RSSI as a fine-scale distance estimator and localization tool using a novel multi-sensor WiFi biologger (WildFi). We conducted four experiments: (1) testing how tag orientation affects RSSI-distance relationships; (2) evaluating whether environmental covariates measured by onboard sensors improve proximity estimates; (3) assessing the accuracy of trilateration-based tag localization using fixed gateway arrays; and (4) comparing RSSI- and GPS-inferred proximity in free-ranging Egyptian fruit bats (Rousettus aegyptiacus). C_LIO_LIWhile RSSI alone could predict distance with reasonable accuracy, incorporating additional tag-sensed information (e.g., temperature, humidity, barometric pressure) and accounting for tag-level heterogeneity significantly improved predictive accuracy. Based on RSSI predictions, we could estimate tag location with a median error of 2.6 meters, accurate enough to indirectly estimate proximity networks without tag-to-tag communication. In deployments on free-flying bats, we found that RSSI and GPS were only weakly concordant, with GPS unreliable for detecting fine-scale interactions (<50 m). In contrast, RSSI could capture both fine-scale and some long-range interactions up to [~]250m. C_LIO_LIThese findings highlight RSSIs potential as a robust metric for proximity logging, particularly when combined with multi-sensor data and pre-deployment validations. Integrating multi-sensor data streams further enhances RSSI interpretability. Future biologger designs should prioritize synergy among data streams for integrated insights into proximity and animal behavior. C_LI Data and code for peer review statementData and code to reproduce the results of the paper are provided in a zip folder for peer review. We also provided our compiled code.

ecology↗
bioRxiv2025

Timing of independence is explained by movement ability, but depends on how independence is defined for a long-lived raptor

Many young animals must gain independence from parental care by acquiring the necessary skills for survival. Thus, the rate of skill acquisition can predict how long juveniles remain with their parents before emigrating from the natal territory. Yet in some systems, young animals acquire adult-like skills and the capacity to be independent long before they emigrate. This raises the question of why the timing of emigration decouples from the rate of skill acquisition, resulting in extended parental care. We addressed this by leveraging GPS tracking data from juvenile golden eagles (Aquila chrysaetos), which learn to fly and to hunt while remaining with their parents for 61-283 days after fledging. Young golden eagles often go on excursions without their parents outside of their natal territories before emigration. We expected flight performance to predict the timing of excursions better than the timing of emigration, which should be more influenced by external factors. In a set of time-to-event models, we predicted the rate of excursions and of emigration using metrics of soaring flight performance or of daily movement. Contrary to our prediction, we found that soaring performance failed to predict the rate of either excursions or emigration, whereas daily movement predicted both rates, but inconsistently. This was likely because those coarser metrics captured motivation and weather in addition to flight skills. Thus external factors seem more likely to explain the timing of independence and internal development--in this case of flight skills--may be completed quickly. Juveniles may delay emigration not due to lack of skill, but because the costs of leaving parental care outweigh the benefits. The difference we discovered between when individuals were capable of independence and when they committed to it may obscure the more general link between skill acquisition and the end of parental care in other systems as well.

animal behavior and cognition↗
bioRxiv2025

MoveTraits - A database for integrating animal behaviour into trait-based ecology

Trait-based approaches are key to understanding eco-evolutionary processes but rarely account for animal behaviour despite its central role in ecosystem dynamics. We propose integrating behaviour into trait-based ecology through movement traits - standardised and comparable measures of animal movement derived from biologging data, such as daily displacements or range sizes. Accounting for animal behaviour will advance trait-based research on species interactions, community structure, and ecosystem functioning. Importantly, movement traits allow for quantification of behavioural reaction norms, offering insights into species acclimation and adaptive capacity to environmental change. We outline a vision for a living global movement trait database that enhances trait data curation by (1) continuously growing alongside shared biologging data, (2) calculating traits directly from individual-level data using standardised, consistent methodology, and (3) providing information on multi-level (species, individual, within-individual) trait variation. We present a proof-of-concept MoveTraits database with 55 mammal and 108 bird species, demonstrating calculation workflows for 5 traits across multiple time scales. Movement traits have significant potential to improve trait-based global change predictions and contribute to global biodiversity assessments as Essential Biodiversity Variables. By making animal movement data more accessible and interpretable, this database could bridge the gap between movement ecology and biodiversity policy, facilitating evidence-based conservation.

ecology↗
bioRxiv2024

Golden eagles regularly use gravity waves to soar in the Alps: new insights from high-resolution weather data

1Soaring flight developed as a result of behavioural and morphological adaptations that allow birds to reduce the metabolic cost of flight by harnessing the energy available in the atmosphere. Despite an increased attention given in the last decades to the physics and ecology that allow soaring flight, its study has been limited by the generally low spatio-temporal resolution of available atmospheric data. This constrained our ability to quantify the atmospheric conditions that allow soaring, and limited our understanding of its flexibility in different uplift conditions. While the use of updraughts such as thermals and orographic lifting are well described in the literature (albeit only quantified through atmospheric proxies), the use of others, such as gravity waves, was hypothesised but largely undocumented. Recent advancements in high-resolution atmospheric modelling, with hourly output available at the kilometer-scale grid spacing, offer new opportunities to investigate the flexibility of soaring flight in response to complex atmospheric dynamics. In this study, we used a combination of a high-resolution atmospheric analysis and high-resolution GPS tracking data to characterise the updraught sources used by golden eagles, Aquila chrysaetos, in the European Alps. We document that golden eagles in this region repeatedly use gravity waves, and that while thermals were still the main updraught source used for soaring, gravity waves were involved in at least 19% of the inspected soaring segments. In winter, when thermals were more scarce, the quasi-totality of soaring events were powered by gravity waves or orographic lifting, largely expanding the environmental energy available to soaring birds and therefore the landscape connectivity in topographically complex regions. Our results also emphasise the difficulty to distinguish between convective (thermals) and dynamic updraught sources, as these co-occur within the boundary layer over complex terrain.

ecology↗
bioRxiv2023

Gaining proficiency in flight transforms energy landscapes during ontogeny

The heterogeneity of the physical environment determines the cost of transport for animals, shaping their energy landscape. Animals respond to this energy landscape by adjusting their distribution and movement to maximize gains and reduce costs. Much of our knowledge about energy landscape dynamics focuses on factors external to the animal, particularly the spatio-temporal variations of the environment. However, an animals internal state can significantly impact its ability to perceive and utilize available energy, creating a distinction between the "fundamental" and the "realized" energy landscapes. Here we show that the realized energy landscape varies along the ontogenetic axis. Locomotor and cognitive capabilities of individuals change over time, especially during the early life stages. We investigate the development of the realized energy landscape in the Central European Alpine population of the golden eagle Aquila chrysaetos, a large predator that requires negotiating the atmospheric environment to achieve energy-efficient soaring flight. We quantified weekly energy landscapes using environmental features for 55 juvenile golden eagles, demonstrating that energetic costs of traversing the landscape decreased with age. Consequently, the potentially flyable area within the Alpine region increased 2,170-fold during their first three years of independence. Our work contributes to a predictive understanding of animal movement by presenting ontogeny as a mechanism shaping the realized energy landscape.

animal behavior and cognition↗
bioRxiv2023

Conserving bird populations in the Anthropocene: the significance of non-breeding movements

Advances in tracking technologies have revealed the diverse migration patterns of birds, which are critical for range mapping and population estimation. Population trends are usually estimated in breeding ranges where birds remain stationary, but for species that breed in remote areas like the Arctic, these trends are often assessed in over-wintering ranges. Evaluating population trends during the wintering season is challenging due to the extensive movements of birds in these ranges, which require a deep understanding of the movement dynamics. However, these movements remain understudied, particularly in the mid-latitudes, where many Arctic breeders overwinter, increasing uncertainty in their ranges and numbers. Here, we show that the Arctic breeding raptor Rough-legged buzzard, which overwinters in the mid-latitudes, has a specific wintering strategy. After migrating ca 1,500 km from the Arctic to mid-latitudes, the birds continue to move throughout the entire over-wintering period, covering an additional 1,000 km southwestward and then back northeastward as the snowline advances. This ongoing movement makes their wintering range dynamic over the course of the season. In essence, this movement represents an extension of the quick migration process, albeit at a slower pace, and we have termed this migration pattern foxtrot migration, drawing an analogy to the alternating fast and slow movements of the foxtrot dance. These results highlight the potential errors in range mapping from single mid-winter surveys and emphasize the importance of this migration pattern in assessing the conservation status of bird species. Understanding this migration pattern could help to correctly estimate bird populations in over-wintering ranges, which is especially important for species that nest in hard-to-reach regions such as the Arctic.

ecology↗
bioRxiv2022

The role of wingbeat frequency and amplitude in flight power

Body-mounted accelerometers provide a new prospect for estimating power use in flying birds, as the signal varies with the two major kinematic determinants of aerodynamic power: wingbeat frequency and amplitude. Yet wingbeat frequency is sometimes used as a proxy for power output in isolation. There is therefore a need to understand which kinematic parameter birds vary and whether this is predicted by flight mode (e.g., accelerating, ascending/descending flight), speed or morphology. We investigate this using high-frequency acceleration data from (i) 14 species flying in the wild, (ii) two species flying in controlled conditions in a wind tunnel and (iii) a review of experimental and field studies. While wingbeat frequency and amplitude were positively correlated, R2 values were generally low, supporting the idea that parameters can vary independently. Indeed, birds were more likely to modulate wingbeat amplitude for more energy-demanding flight modes, including climbing and take-off. Nonetheless, the striking variability even within species and flight types, highlights the complexity of describing the kinematic relationships, which appear sensitive to both the biological and physical context. Notwithstanding this acceleration metrics that incorporate both kinematic parameters should be more robust proxies for power than wingbeat frequency alone.

biophysics↗
bioRxiv2022

Extreme tolerable winds for seabirds are determined by morphology

Storms can cause widespread seabird strandings and wrecking1,2,3,4,5, yet little is known about the maximum wind speeds that birds are able to tolerate or the conditions they avoid. We analyzed > 300,000 hours of tracking data from 18 seabird species, including flapping and soaring fliers, to assess how flight morphology affects wind selectivity, both at fine scales (hourly movement steps) and across the breeding season. We found no general preference or avoidance of particular wind speeds within foraging tracks. This suggests seabird flight morphology is adapted to a "wind niche", with higher wing loading being selected for in windier environments. In support of this, wing loading was positively related to the median wind speeds on the breeding grounds, as well as the maximum wind speeds in which birds flew. Yet globally, the highest wind speeds occur in the tropics (in association with tropical cyclones) where birds are morphologically adapted to low median wind speeds. Tropical species must therefore show behavioral responses to extreme winds, including long-range avoidance of wind speeds that can be twice their operable maxima. In contrast, procellariiformes flew in almost all wind speeds they encountered at a seasonal scale. Despite this, we describe a small number of cases where albatrosses avoided strong winds at close-range, including by flying into the eye of the storm. Extreme winds appear to pose context- dependent risks to seabirds, and more information is needed on the factors that determine the hierarchy of risk, given the impact of global change on storm intensity 6,7.

animal behavior and cognition↗
bioRxiv2022

MoveApps - a serverless no-code analysis platform for animal tracking data

BackgroundBio-logging and animal tracking datasets continuously grow in volume and complexity, documenting animal behaviour and ecology in unprecedented extent and detail, but greatly increasing the challenge of extracting knowledge from the data obtained. A large variety of analysis methods are being developed, many of which in effect are inaccessible to potential users, because they remain unpublished, depend on proprietary software or require significant coding skills. ResultsWe developed MoveApps, an open analysis platform for animal tracking data, to make sophisticated analytical tools accessible to a global community of movement ecologists and wildlife managers. As part of the Movebank ecosystem, MoveApps allows users to design and share workflows composed of analysis modules (Apps) that access and analyse tracking data. Users browse Apps, build workflows, customise parameters, execute analyses and access results through an intuitive web-based interface. Apps, coded in R or other programming languages, have been developed by the MoveApps team and can be contributed by anyone developing analysis code. They become available to all user of the platform. To allow long-term and cross-system reproducibility, Apps have public source code and are compiled and run in Docker containers that form the basis of a serverless cloud computing system. To support reproducible science and help contributors document and benefit from their efforts, workflows of Apps can be shared, published and archived with DOIs in the Movebank Data Repository. The platform was beta launched in spring 2021 and currently contains 44 Apps that are used by 156 registered users. We illustrate its use through two workflows that (1) provide a daily report on active tag deployments and (2) segment and map migratory movements. ConclusionsThe MoveApps platform is meant to empower the community to supply, exchange and use analysis code in an intuitive environment that allows fast and traceable results and feedback. By bringing together analytical experts developing movement analysis methods and code with those in need of tools to explore, answer questions and inform decisions based on data they collect, we intend to increase the pace of knowledge generation and integration to match the huge growth rate in bio-logging data acquisition.

ecology↗
bioRxiv2021

Effect of tag attachment on flight parameters and energetic cost across five raptor species

Bio-logging devices play a fundamental and indispensable role in movement ecology studies, particularly in the wild. However, researchers are becoming increasingly aware of the influence that attaching devices can have on animals, particularly on their behaviour, energy expenditure and survival. The way a device is attached to an animals body has also potential consequences for the collected data, and quantifying the type and magnitude of such potential effects is fundamental to enable researchers to combine and compare data from different studies, as much as it is to improve animal welfare. For over two decades, large terrestrial birds have been in the focus of long-term movement ecology research, employing bio-logging devices attached with different types of harnesses. However, comparative studies investigating the effects of different harness types used on these species are scarce. In this study, we tested for potential differences in data collected by two commonly used harness types, backpack and leg-loop, on the flight performance of 10 individuals from five raptor species, equipped with high resolution bio-logging devices, in the same area and time. We explored the effect of harness type on vertical speed, horizontal speed, glide ratio, height above sea level, distance travelled, proportion of soaring and flapping behaviour, and VeDBA (a proxy for energy expenditure) between and within individuals, all used as fine-scale measures of flight performance. Birds equipped with leg-loops climbed up to 0.65 ms-1 faster, reached 19% greater heights while soaring, and spent less time in active flight compared to birds equipped with backpacks, suggesting that backpack harnesses, compared to leg-loops, might cause additional drag affecting the birds flight performance. A lower rate of sinking while gliding, a slightly higher glide ratio, higher horizontal speed while soaring, and lower VeDBA, were also indicative of less drag using leg-loops. Our results add to the existing literature highlighting the design-related advantages of leg-loops, and support the use of leg-loops as a better alternative to backpack harnesses for large soaring birds, when possible. Our study also highlights how apparently small changes in device attachment can lead to notable improvements in tagging practice, with implications for animal welfare, data interpretation and comparability.

animal behavior and cognition↗
bioRxiv2021

Ecological inference using data from accelerometers needs careful protocols

O_LIAccelerometers in animal-attached tags have proven to be powerful tools in behavioural ecology, being used to determine behaviour and provide proxies for movement-based energy expenditure. Researchers are collecting and archiving data across systems, seasons and device types. However, in order to use data repositories to draw ecological inference, we need to establish the error introduced according to sensor type and position on the study animal and establish protocols for error assessment and minimization. C_LIO_LIUsing laboratory trials, we examine the absolute accuracy of tri-axial accelerometers and determine how inaccuracies impact measurements of dynamic body acceleration (DBA), as the main acceleration-based proxy for energy expenditure. We then examine how tag type and placement affect the acceleration signal in birds using (i) pigeons Columba livia flying in a wind tunnel, with tags mounted simultaneously in two positions, (ii) back- and tail-mounted tags deployed on wild kittiwakes Rissa tridactyla. Finally, we (iii) present a case study where two generations of tag were deployed using different attachment procedures on red-tailed tropicbirds Phaethon rubricauda foraging in different seasons. C_LIO_LIBench tests showed that individual acceleration axes required a two-level correction (representing up to 4.3% of the total value) to eliminate measurement error. This resulted in DBA differences of up to 5% between calibrated and uncalibrated tags for humans walking at different speeds. Device position was associated with greater variation in DBA, with upper- and lower back-mounted tags in pigeons varying by 9%, and tail- and back-mounted tags varying by 13% in kittiwakes. Finally, DBA varied by 25% in tropicbirds between seasons, which may be attributable to tag attachment procedures. C_LIO_LIAccelerometer accuracy, tag placement, and attachment details critically affect the signal amplitude and thereby the ability of the system to detect biologically meaningful phenomena. We propose a simple method to calibrate accelerometers that should be used prior to deployments and archived with resulting data, suggest a way that researchers can assess accuracy in previously collected data, and caution that variable tag placement and attachment can increase sensor noise and even generate trends that have no biological meaning. C_LI

animal behavior and cognition↗
bioRxiv2021

The species-specificity of energy landscapes for soaring birds, and its consequences for transferring suitability models across species

O_LISoaring birds use the energy available in the environment in the form of atmospheric uplifts, to subsidize their flight. Their dependence on soaring opportunities makes them extremely sensitive to anthropogenic wind energy development. Predictive modelling is now considered instrumental to forecast the impact of wind farms on single species of concern. However, as multiple species often coexist in the same area, there is clear need to overcome the limitations of single species approaches. C_LIO_LIWe looked for converging patterns in the way two obligate soaring species use the energy available in the landscape to soar, using movement data from 57 white storks, Ciconia ciconia, and 27 griffon vultures, Gyps fulvus. We first compared the soaring efficiency of the two species. We then tested the accuracy of topographic features, important correlates of collision risk in soaring birds, in predicting their soaring behaviour. We finally tested the transferability of soaring suitability models across species. C_LIO_LITopography alone can predict and map the soaring opportunities available to storks across Europe, but not as efficiently in vultures. Only 20.5% of the study area was suitable to both species to soar, suggesting the existence of species-specific requirements in the use of the landscape for soaring. Storks relied on uplift occurrence while vultures on uplift quality, needing stronger uplifts to support their higher body mass and wing loading. C_LIO_LISynthesis and applications: Our results indicate that the flight of highly specialized soaring species is more dependent on atmospheric conditions than on static features, and that more knowledge is required to accurately predict their behaviour. Despite the superficially similar soaring behaviour, the two species have different environmental requirements, suggesting that energy landscapes are species-specific. Our models provide a base to explore the effects that changes in the landscape have on the flight behaviour of different soaring species and suggest that there is no reliable and responsible way to shortcut risk assessment in areas where multiple species might be at risk by anthropogenic structures. C_LI

ecology↗
bioRxiv2021

Fine-scale changes in speed and altitude suggest protean movements in homing pigeon flights

The flight speeds that animals should adopt to minimise energy expenditure in different scenarios can be predicted by the curve of power against speed. However, relatively few studies have examined how animals respond to the landscape below them, which could affect speed through modifications in climb rate and perceived predation risk. We equipped homing pigeons (Columba livia) with high frequency loggers to examine how flight speed varies in relation to topography and land cover, predicting that these parameters may have a substantial impact on flight speed and hence cost. Pigeons showed mixed evidence for an energy saving strategy, as they minimised climb rates by starting their ascent ahead of hills, but selected rapid speeds in their ascents. Birds did not modify their speed substantially in relation to land cover, but higher speeds were observed during descending flight, highlighting the importance to consider the rate of change in altitude before estimating power use from speed. Finally, we document an unexpected variability in speed and altitude over fine scales; a source of substantial inefficiency. We suggest this may a form of protean behaviour adopted to reduce predation risk when flocking is not an option, and that such a strategy could be widespread.

animal behavior and cognition↗
bioRxiv2020

Sea-crossing along migratory flyways is limited more strongly by wind than by lack of uplift

Flying over the open sea is energetically costly for terrestrial birds. Despite this, over-water journeys of many birds, sometimes hundreds of kilometers long, are uncovered by bio-logging technology. To understand how these birds afford their flights over the open sea, we investigated the role of atmospheric conditions, specifically wind and uplift, in subsidizing over-water flight at the global scale. We first established that {Delta}T, the temperature difference between sea surface and air, is a meaningful proxy for uplift over water. Using this proxy, we showed that the spatio-temporal patterns of sea-crossing in terrestrial migratory birds is associated with favorable uplift conditions. We then analyzed route selection over the open sea for five facultative soaring species, representing all major migratory flyways. The birds maximized wind support when selecting their sea-crossing routes and selected higher uplift when suitable wind support was available. They also preferred routes with low long-term uncertainty in wind conditions. Our findings suggest that, in addition to wind, uplift may play a key role in the energy seascape for bird migration that in turn determines strategies and associated costs for birds crossing ecological barriers such as the open sea.

animal behavior and cognition↗
bioRxiv2020

Wing tags severely impair movement in African Cape Vulture

BackgroundThe use of tracking technologies is key for the study of animal movement and pivotal to ecological and conservation research. However, the potential effects of devices attached to animals are sometimes neglected. The impact of tagging not only rises welfare concerns, but can also bias the data collected, causing misinterpretation of the observed behaviour which invalidates the comparability of information across individuals and populations. Patagial (wing) tags have been extensively used as a marking method for visual resightings in endangered vulture species, but their effect on the aerodynamics of the birds and their flight behaviour is yet to be investigated. Using GPS backpack mounted devices, we compared the flight performance of 27 captive and wild Cape Vultures (Gyps coprotheres), marked with either patagial tags or coloured leg bands. ResultsIndividuals equipped with patagial tags were less likely to fly, travelled shorter distances and flew slower compared to individuals equipped with leg bands. These effects were also observed in one individual that recovered its flight performance after replacing its patagial tag by a leg band. ConclusionsAlthough we did not measure the effects of patagial tags on body condition or survival, our study strongly suggests that they have severe adverse effects on vultures flight behaviour and emphasises the importance of investigating the effects that tagging methods can have on the behaviour and conservation of the study species, as well as on the quality of the scientific results.

animal behavior and cognition↗