Search

During early development, juvenile animals need to acquire a diverse behavioural repertoire to interact with their environment. The ontogeny of animal behaviour, is paced by the motivation to improve, e.g. internal clocks, and limited by external constraints, e.g. weather conditions. We here evaluate how naive Egyptian vultures ( Neophron percnopterus ) improve in locomotor performance, measured as daily maximum displacement, prior to their first migration under three different time constraint regimes: we compared wild hatched vultures, migrating one month after fledging, with captive-hatched vultures, released in spring four months or in winter nine months before migration. We found that the time until migration paced the development of movement behaviour: wild birds rapidly increased displacement distances within the first two weeks after fledging, while spring and winter released vultures delayed movement increases by two and four months, respectively. Under relaxed time constraints captive-hatched vultures displayed diverse functional forms of performance enhancements and therefore great variability in individual ontogeny of movement behaviour. While weather conditions in winter could limit flight movements, some birds indeed moved immediately after their release, indicating that weather may not be limiting. Our findings promote the idea that relaxed ecological constraints could uncover hidden phenotypic flexibility in ontogeny, which could present a greater potential for adaptability under environmental change than currently expected.

Global movement patterns of migratory birds illustrate their fascinating physical and physiological abilities to cross continents and oceans. During their voyages, most birds land multiple times to make so-called 'stopovers'. Our current knowledge on the functions of stopover is mainly based on the proximate study of departure decisions. However, such studies are insufficient to gauge fully the ecological and evolutionary functions of stopover. If we study how a focal trait, e.g. changes in energy stores, affects the decision to depart from a stopover without considering the trait(s) that actually caused the bird to land, e.g. unfavourable environmental conditions for flight, we misinterpret the function of the stopover. It is thus important to realise and acknowledge that stopovers have many different functions, and that not every migrant has the same (set of) reasons to stop-over. Additionally, we may obtain contradictory results because the significance of different traits to a migrant is context dependent. For instance, late spring migrants may be more prone to risk-taking and depart from a stopover with lower energy stores than early spring migrants. Thus, we neglect that departure decisions are subject to selection to minimise immediate (mortality risk) and/or delayed (low future reproductive output) fitness costs. To alleviate these issues, we first define stopover as an interruption of migratory endurance flight to minimise immediate and/or delayed fitness costs. Second, we review all probable functions of stopover, which include accumulating energy, various forms of physiological recovery and avoiding adverse environmental conditions for flight, and list potential other functions that are less well studied, such as minimising predation, recovery from physical exhaustion and spatiotemporal adjustments to migration. Third, derived from these aspects, we argue for a paradigm shift in stopover ecology research. This includes focusing on why an individual interrupts its migratory flight, which is more likely to identify the individual-specific function(s) of the stopover correctly than departure-decision studies. Moreover, we highlight that the selective forces acting on stopover decisions are context dependent and are expected to differ between, e.g. K-/r-selected species, the sexes and migration strategies. For example, all else being equal, r-selected species (low survival rate, high reproductive rate) should have a stronger urge to continue the migratory endurance flight or resume migration from a stopover because the potential increase in immediate fitness costs suffered from a flight is offset by the expected higher reproductive success in the subsequent breeding season. Finally, we propose to focus less on proximate mechanisms controlling landing and departure decisions, and more on ultimate mechanisms to identify the selective forces shaping stopover decisions. Our ideas are not limited to birds but can be applied to any migratory species. Our revised definition of stopover and the proposed paradigm shift has the potential to stimulate a fruitful discussion towards a better evolutionary ecological understanding of the functions of stopover. Furthermore, identifying the functions of stopover will support targeted measures to conserve and restore the functionality of stopover sites threatened by anthropogenic environmental changes. This is especially important for long-distance migrants, which currently are in alarming decline.

Millions of birds travel every year between Europe and Africa detouring ecological barriers and funnelling through migratory corridors where they face variable weather conditions. Little is known regarding the response of migrating birds to mesoscale meteorological processes during flight. Specifically, sea-breeze has a daily cycle that may directly influence the flight of diurnal migrants. We collected radar tracks of soaring migrants using modified weather radar in Latrun, central Israel, in 7 autumns between 2005 and 2016. We investigated how migrating soaring birds adjusted their flight speed and direction under the effects of daily sea-breeze circulation. We analysed the linear and, uniquely, the non-linear effects of wind on bird ground-, air- and sideways speed as function of time along the day using Generalized Additive Mixed Models and calculated first derivatives to identify when birds adjusted their response to the wind over time. Using data collected during a total of 148 days, we characterised the diel dynamics of horizontal wind flow in its two vectorial components relative to soaring migration goal (South), finding a consistent rotational movement of the wind blowing towards the East (morning) and to the South-East (late afternoon), with highest speed of crosswind component around mid-day and increasing tailwinds towards the late afternoon. We found that the airspeed of radar detected birds decreased consistently with increasing tailwind throughout the day, resulting in a rather stable groundspeed of 16-17 m/s. In addition, birds increased their sideways speed when crosswinds were at their maximum to an extent similar to that of the wind’s sideways component, meaning a full compensation to wind drift, which decreased after the time of crosswind maximum. Using a simple, novel and broadly applicable statistical method, we studied, for the first time, how wind influences bird flight by highlighting non-linear effects over time, providing new insights regarding the behavioural adjustments in the response of soaring birds to wind conditions. Our work enhances our understanding of how migrating birds respond to changing wind conditions during their journeys in order to exploit migratory corridors.

Environmental conditions, including weather, influence organisms in a variety of ways. Specifically, animal males and females might be affected differently by ambient temperatures that vary in time and space. In this study, we explored the effect of elevation, which strongly determines ambient temperatures, on the speed of moult of the wing’s flight feathers in the Eurasian Blackbird (Turdus merula). Differences in moult speed may alter the wing’s surface area during the moulting process and hence may influence flight performance, including the ability to escape from predators. Sampling elevations were categorized to locations > 1000 m above mean sea level (AMSL) and locations

Space-based tracking technology using low-cost miniature tags is now delivering data on fine-scale animal movement at near-global scale. Linked with remotely sensed environmental data, this offers a biological lens on habitat integrity and connectivity for conservation and human health; a global network of animal sentinels of environmental change. Publisher PDF

Large‐scale spatial gradients of environmental conditions shape organisms, populations and ecosystems. Even though environmental gradients are a key research theme in macro‐ecology and biogeography, the effects of large‐scale, east–west, environmental gradients are largely overlooked compared with north–south gradients. Our study focused on feather moult, an important and energy demanding process in birds. By comparing Western and Eastern Palearctic populations of 21 species, we found that juvenile passerines in the Western and Eastern Palearctic differ in the number of feathers moulted as part of their post‐juvenile moult. This difference is most likely the result of a large‐scale climatic gradient in cold season duration and consequent differences in the time available for moulting. Eastern populations were characterized by a limited extent of feather moult that was additionally affected by migration distance and body mass. The longer migration distance in the Eastern Palearctic caused a generally less extensive moult while high body mass was correlated with a low difference in moult extent between the Western and Eastern Palearctic regions. These results highlight the importance of linking annual cycle processes at the organismal level to the specific environmental conditions within the distribution range of each species.

Reintroducing species to their historic range or reinforcing extant but endangered populations with individuals from elsewhere are popular conservation efforts to maintain long-term viable populations of animals. These efforts, known as conservation translocations, require proper monitoring of the fate of the animals that are released to assess their success. Nevertheless, effective monitoring is often missing in conservation translocations. Here, we assessed the efficiency of different monitoring methods and estimated survival of captive-bred Egyptian Vultures (Neophron percnopterus) that were released to the wild during the first 15 years of a reintroduction project in Israel. First, we inspected data obtained from different monitoring methods and compared observations of color rings and wing tags to location data from GPS transmitters. Then, we used GPS data to estimate apparent survival of vultures that were released to the wild at different ages and different seasons. Finally, we compared the apparent survival of captive-bred and wild-hatched Egyptian Vultures. We show that only a relatively small portion of the birds were visually observed through color rings and wing tags, compared to those for which data were obtained from GPS transmitters. Using data obtained via GPS transmitters we were able to show that release age and season did not alter apparent survival. In addition, we found no differences in apparent survival between captive-bred and wild-hatched Egyptian Vultures during their first migration or during their first two years postrelease or postfledging. Our results show the importance of continuous and effective monitoring and confirm the efficacy of captive-breeding and release of Egyptian Vultures as a conservation tool. We recommend the continuation of monitoring using GPS transmitters, alongside increased observation-based monitoring efforts.

Males and females are often influenced by different selective forces, frequently resulting in diverging phenotypes, for example in colouration. Since an animal's colouration may strongly influence its fitness, causes and consequences of sexual dichromatism in birds could aid in understanding important factors affecting sexual and natural selection. Variation in plumage ornamentation may affect mate attraction or intraspecific antagonistic behaviour. In most passerines, body plumage colouration of juveniles is obtained through the process of feather moult. The number of moulted wing and tail feathers, which also influences the bird's appearance, may affect its fitness. Here, we show that body plumage colouration of male, but not female, passerines is correlated with the number of moulted wing and tail feathers in the early stage of the bird's life for both sexes. Thus, the extent of wing and tail moult in females is not modulated by the female's colouration and can prevent females from reaching their sex-specific optima. This result could be explained by high intersexual genetic correlations, which might make it impossible for the sexes to reach their own trait fitness optima. Our findings may indicate that species-specific, rather than sex-specific, internal correlations shaped bird moult strategy, an important avian life-history trait.

The evolutionary history of many organisms is characterized by major changes in morphology and distribution. Specifically, alterations of body mass and geographic distribution may profoundly influence organismal life-history traits. Here, we reconstructed the evolutionary history of flight-feather molt strategy using data from 1,808 Neornithes species. Our analysis suggests that the ancestral molt strategy of first-year birds was partial or entirely absent, and that complete wing flight-feather molt in first-year birds first evolved in the late Eocene and Oligocene (25–40 Ma), at least 30 Myr after birds first evolved. Complete flight-feather molt occurred mainly at equatorial latitudes and in relatively low body mass species, following a diversification of body mass within the lineage. We conclude that both body mass and geographic distribution shaped the evolution of molt strategies and propose that the evolutionary transition towards complete juvenile molt in the Neornithes is a novel, relatively late adaptation.

Nomadism is a type of movement lacking fixed spatiotemporal patterns, evident in species inhabiting variable environments. The irregular movement characterizing nomadic species often acts as a challenging barrier for scientists investigating their ecology. We provide an insight on the movement of a nomadic desert bird, the Spotted Sandgrouse (Pterocles senegallus), within and between different activity seasons. The data were obtained from 1 individual fitted with a satellite transmitter, which was tracked for ∼2.5 years. Three main activity seasons were detected during which the bird stayed in a specific area: pre-breeding, breeding, and winter. Nomadic behavior was evident during the pre-breeding and breeding seasons, whereas site fidelity was observed during winter (i.e., seasonal nomadism). Local scale fidelity with respect to roosting behavior was also evident among and within the 3 winters of tracking. Field observations carried out during the first breeding season enabled us to link the movement patterns of the bird with its behavior at different phases of the breeding season. Within and between activity seasons, the bird was engaged in short- and long-distance scouting forays. The long-distance ones occurred only during the pre-breeding season. In some of the scouting forays, the bird arrived at sites it had previously utilized, suggesting the existence of spatial memory and navigation capability. This fine-scale description of movement can uncover key features, which allow the survival and reproduction of nomadic birds inhabiting arid areas where the distribution of resources is largely unpredictable.

Nocturnal avian migration flyways remain an elusive concept, as we have largely lacked methods to map their full extent. We used the network of European weather radars to investigate nocturnal bird movements at the scale of the European flyway. We mapped the main migration directions and showed the intensity of movement across part of Europe by extracting biological information from 70 weather radar stations from northern Scandinavia to Portugal, during the autumn migration season of 2016. On average, over the 20 nights and all sites, 389 birds passed per 1 km transect per hour. The night with highest migration intensity showed an average of 1621 birds km–1 h–1 passing the radar stations, but there was considerable geographical and temporal variation in migration intensity. The highest intensity of migration was seen in central France. The overall migration directions showed strong southwest components. Migration dynamics were strongly related to synoptic wind conditions. A wind‐related mass migration event occurred immediately after a change in wind conditions, but quickly diminished even when supporting winds continued to prevail. This first continental‐scale study using the European network of weather radars demonstrates the wealth of information available and its potential for investigating large‐scale bird movements, with consequences for ecosystem function, nutrient transfer, human and livestock health, and civil and military aviation.

1. Long‐distance migrations are among the most physically demanding feats animals perform. Understanding the potential costs and benefits of such behaviour is a fundamental question in ecology and evolution. A hypothetical cost of migration should be outweighed by higher productivity and/or higher annual survival, but few studies on migratory species have been able to directly quantify patterns of survival throughout the full annual cycle and across the majority of a species’ range. 2. Here, we use telemetry data from 220 migratory Egyptian vultures Neophron percnopterus, tracked for 3,186 bird months and across approximately 70% of the species’ global distribution, to test for differences in survival throughout the annual cycle. 3. We estimated monthly survival probability relative to migration and latitude using a multi‐event capture–recapture model in a Bayesian framework that accounted for age, origin, subpopulation and the uncertainty of classifying fates from tracking data. 4. We found lower survival during migration compared to stationary periods (β = −0.816; 95% credible interval: −1.290 to −0.318) and higher survival on non‐breeding grounds at southern latitudes (

Early-life conditions have critical, long-lasting effects on the fate of individuals, yet early-life activity has rarely been linked to subsequent survival of animals in the wild. Using high-resolution GPS and body-acceleration data of 93 juvenile white storks (Ciconia ciconia), we examined the links between behaviour during both pre-fledging and post-fledging (fledging-to-migration) periods and subsequent first-year survival. Juvenile daily activity (based on overall dynamic body acceleration) showed repeatable between-individual variation, the juveniles' pre- and post-fledging activity levels were correlated and both were positively associated with subsequent survival. Daily activity increased gradually throughout the post-fledging period, and the relationship between post-fledging activity and survival was stronger in individuals who increased their daily activity level faster (an interaction effect). We suggest that high activity profiles signified individuals with increased pre-migratory experience, higher individual quality and perhaps more proactive personality, which could underlie their superior survival rates. The duration of individuals’ fledging-to-migration periods had a hump-shaped relationship with survival: higher survival was associated with intermediate rather than short or long durations. Short durations reflect lower pre-migratory experience, whereas very long ones were associated with slower increases in daily activity level which possibly reflects slow behavioural development. In accordance with previous studies, heavier nestlings and those that hatched and migrated earlier had increased survival. Using extensive tracking data, our study exposed new links between early-life attributes and survival, suggesting that early activity profiles in migrating birds can explain variation in first-year survival.

Seasonal animal migration is a widespread phenomenon. At the species level, it has been shown that many migratory animal species track similar climatic conditions throughout the year. However, it remains unclear whether such a niche tracking pattern is a direct consequence of individual behaviour or emerges at the population or species level through behavioural variability. Here, we estimated seasonal niche overlap and seasonal niche tracking at the individual and population level of central European white storks ( Ciconia ciconia ). We quantified niche tracking for both weather and climate conditions to control for the different spatio-temporal scales over which ecological processes may operate. Our results indicate that niche tracking is a bottom-up process. Individuals mainly track weather conditions while climatic niche tracking mainly emerges at the population level. This result may be partially explained by a high degree of intra- and inter-individual variation in niche overlap between seasons. Understanding how migratory individuals, populations and species respond to seasonal environments is key for anticipating the impacts of global environmental changes.

Although feathers are the unifying characteristic of all birds, our understanding of the causes, mechanisms, patterns and consequences of the feather moult process lags behind that of other major avian life-history phenomena such as reproduction and long-distance migration. Migration, which evolved in many species of the temperate and arctic zones, requires high energy expenditure to endure long-distance journeys. About a third of Western-Palearctic passerines perform long-distance migrations of thousands of kilometres each year using various morphological, physiological, biomechanical, behavioural and life-history adaptations. The need to include the largely non-overlapping breeding, long-distance migration and feather moult processes within the annual cycle imposes a substantial constraint on the time over which the moult process can take place. Here, we review four feather-moult-related adaptations which, likely due to time constraints, evolved among long-distance Western-Palearctic migrants: (i) increased moult speed; (ii) increased overlap between moult and breeding or migration; (iii) decreased extent of plumage moult; and (iv) moult of part or all of the plumage during the over-wintering period in the tropics rather than in the breeding areas. We suggest that long-distance migration shaped the evolution of moult strategies and increased the diversity of these strategies among migratory passerines. In contrast to this variation, all resident passerines in the Western Palearctic moult immediately after breeding by renewing the entire plumage of adults and in some species also juveniles, while in other species juvenile moult is partial. We identify important gaps in our current understanding of the moult process that should be addressed in the future. Notably, previous studies suggested that the ancestral moult strategy is a post-breeding summer moult in the Western Palearctic breeding areas and that moult during the winter evolved due to the scheduling of long-distance migration immediately after breeding. We offer an alternative hypothesis based on the notion of southern ancestry, proposing that the ancestral moult strategy was a complete moult during the 'northern winter' in the Afro-tropical region in these species, for both adults and juveniles. An important aspect of the observed variation in moult strategies relates to their control mechanisms and we suggest that there is insufficient knowledge regarding the physiological mechanisms that are involved, and whether they are genetically fixed or shaped by environmental factors. Finally, research effort is needed on how global climate changes may influence avian annual routines by altering the scheduling of major processes such as long-distance migration and feather moult.

Increased human-induced environmental changes and global warming alter bird migration timing and routes. Recently, many Holarctic species, including white storks, Ciconia ciconia, were reported to overwinter at higher latitudes, closer to breeding grounds. We aimed to understand the causes and implications of this phenomenon by examining bird survival and behaviour during overwintering in Europe versus Africa. We compared GPS and body acceleration data of 54 juvenile (first-year) white storks that originated from the same European natal population and overwintered in Europe or Africa. All six juveniles that overwintered in Europe survived through their first year, which was significantly higher than only 38% of the 48 overwintering in the species' traditional grounds in Africa. During overwintering, storks in Europe differed from those in Africa by (1) reducing movement and foraging range, (2) spending less time flying and more time resting, thus using less energy (estimated from overall dynamic body acceleration) and (3) reducing foraging effort, while relying more on anthropogenic resources (landfills and agricultural areas). Timing affected overwintering site as juveniles that overwintered in Europe hatched and started migrating later. We emphasize, however, that late hatching by itself did not yield a survival benefit as not all late juveniles curtailed their migration. We suggest that wintering in Europe was less demanding compared to Africa which may explain the increased survival of juveniles that wintered in Europe. Our findings correspond to the general increase in the European wintering population of white storks, and shed light on the contemporary trend of shortened bird migration; a phenomenon with potentially broad ecological implications. published

Time constraints influence various ecological, life-history, and demographic properties of individuals and populations of many species throughout the annual cycle. Feather molt is a timely undertaking that is considered among the three most energy-demanding processes in the life cycle of birds. To deal with time pressure, passerines may shorten their molt duration, using three non-mutually exclusive mechanisms: (1) replacing only part of the plumage, (2) increasing the speed of molt, and (3) postponing the renewal of some or all the plumage to a later season (i.e., from the summer to the overwintering period). We used a comparative approach by measuring 12,349 individuals from 134 passerine species to explore how feather molt of juvenile and adult passerines is evolutionarily modulated under time constraints. The results indicate that breeding at northern latitudes and long-distance migration limit the time available for molt and that the consequences of time constraints were age dependent. While the duration of adult summer molt decreased, the extent, rather than the duration, of juvenile molt declined under time constraints. This study highlights the importance of considering time constraints in order to enhance the understanding of selective forces that shape life-history processes and their consequences throughout the annual routine.

Studying the causes and consequences of route selection in animal migration is important for understanding the evolution of migratory systems and how they may be affected by environmental factors at various spatial and temporal scales. One key decision during migration is whether to cross “high transport cost” areas, or to circumvent them. Soaring birds may face this choice when encountering waterbodies where convective updrafts are weak or scarce. Crossing these waterbodies requires flying using energetically costly flapping flight, while circumventing them over land permits energetically cheap soaring.We tested how several atmospheric factors (e.g., wind, thermal uplift) and geographic, seasonal and state-related factors (sex and age) affected route selection in migrating white storks (Ciconia ciconia). We used 196 GPS tracks of 70 individuals either crossing or circumventing the north-easternmost section of the Mediterranean Sea, over Iskenderun Bay in southern Turkey.We found that westward and southward winds promoted a cross-bay journey in spring and autumn, respectively, acting as tailwinds. Also, overall weaker winds promoted a sea crossing in spring. Sea crossing was associated with flapping flight and higher values of Overall Dynamic Body Acceleration (ODBA) and resulted in higher ground speed than travel over land.The combined environmental conditions and the effects of route selection on movement-related energy costs and speed were likely responsible for an increase in the time spent flying and distance travelled of migrating storks that decided to cross the bay during spring. Notably, daily travel distances of spring migrants crossing the bay were 60 kilometres longer than those of land-detouring birds, allowing them to reach their destination faster but likely incurring a higher energetic flight cost. No such benefit was found during autumn.Our findings confirm that atmospheric conditions can strongly affect bird route selection. Consequently, migration timing, speed and movement-related energy expenditure differed considerably between the two migratory seasons and the two route choices, highlighting a time-energy trade-off in the migration of white storks.

Global warming alters various avian phenological processes, including advanced reproduction and migration schedules. In birds, individual appearance is largely determined by plumage, influencing, for example, bird attractiveness, social status and camouflage. Juveniles of most passerine species replace their nest-grown plumage during the first months of life, a process that is called post-juvenile feather moult. Using data from ten natural history collections, we show that the extent of the post-juvenile moult has increased significantly over the last 212 years (1805–2016), a trend that is positively correlated with the temperature of the environment. Therefore, it seems that birds replaced more feathers under warmer conditions, causing juveniles to appear more similar to adult birds. Moreover, in several species, we describe a male–female switch in the extent of moult, with females currently replacing more feathers than males compared to the past. These results demonstrate different biological responses to climate warming by different phenotypes., Most passerine bird species replace part of their plumage within the first year of life. Here, using data from 4,012 individuals of 19 species, Kiat et al. find that the extent of post-juvenile moult has increased over the past 212 years and this correlated with the global temperature increase in this period.

Large parts of the continents are continuously scanned by terrestrial weather radars to monitor precipitation and wind conditions. These systems also monitor the mass movements of bird, bat, and insect migration, but it is still unknown how many of these systems perform with regard to detection and quantification of migration intensities of the different groups. In this study that was undertaken within five regions across Europe and the Middle East we examined to what extent bird migration intensities derived from different weather radars are comparable between each other and relate to intensities measured by local small‐scaled radars, some of them specifically developed to monitor birds. Good correspondence was found for the relative day‐to‐day pattern in migration intensities among most radar systems that were compared. Absolute intensities varied between different systems and regions. The findings of this study can be used to infer about absolute bird migration intensities measured by different radar systems and consequently help resolving methodological issues regarding the estimation of migrant numbers in the Western‐Palearctic region. It further depicts a scientific basis for the future monitoring of migratory bird populations across a large spatio‐temporal scale, predicting their movements and studying its consequences on ecological systems and human lives. We thank, Klaus Stephan (‘Deutscher Wetterdienst’ DWD), Cédric Legal (Météo France) and Günther Haase (BALTRAD, SMHI) for supporting the access to the WR data. We acknowledge the European Operational Program for Exchange of Weather Radar Information (EUMETNET/OPERA) for providing access to European radar data, faciliated through a research-only license agreement between EUMETNET/OPERA members and ENRAM. We thank Femern A/S for allowing us to publish data from the EIA (northern Germany). We thank Asaf Mayrose for facilitating radar data processing and analysis from northern Israel. We thank two reviewers for their helpful comments.Funding – The study was financially support by COST – European Cooperation in Science and Technology – through the Action ES1305 ‘European Network for the Radar Surveillance of Animal Movement’ (ENRAM) for facilitating international collaboration. The Belgian case-study was part of the project RAVEN, which was funded by the Belgian Federal Science Policy office (BELSPO) under the BRAIN-be programme.

Aim: Animal movement is an important determinant of individual survival, population dynamics and ecosystem structure and function. Nonetheless, it is still unclear how local movements are related to resource availability and the spatial arrangement of resources. Using resident bird species and migratory bird species outside the migratory period, we examined how the distribution of resources affects the movement patterns of both large terrestrial birds (e.g., raptors, bustards and hornbills) and waterbirds (e.g., cranes, storks, ducks, geese and flamingos). Location: Global. Time period: 2003–2015. Major taxa studied: Birds. Methods: We compiled GPS tracking data for 386 individuals across 36 bird species. We calculated the straight‐line distance between GPS locations of each individual at the 1‐hr and 10‐day time‐scales. For each individual and time‐scale, we calculated the median and 0.95 quantile of displacement. We used linear mixed‐effects models to examine the effect of the spatial arrangement of resources, measured as enhanced vegetation index homogeneity, on avian movements, while accounting for mean resource availability, body mass, diet, flight type, migratory status and taxonomy and spatial autocorrelation. Results: We found a significant effect of resource spatial arrangement at the 1‐hr and 10‐day time‐scales. On average, individual movements were seven times longer in environments with homogeneously distributed resources compared with areas of low resource homogeneity. Contrary to previous work, we found no significant effect of resource availability, diet, flight type, migratory status or body mass on the non‐migratory movements of birds. Main conclusions: We suggest that longer movements in homogeneous environments might reflect the need for different habitat types associated with foraging and reproduction. This highlights the importance of landscape complementarity, where habitat patches within a landscape include a range of different, yet complementary resources. As habitat homogenization increases, it might force birds to travel increasingly longer distances to meet their diverse needs. National Trust for Scotland; Penguin Foundation; The U.S. Department of Energy, Grant/Award Number: DE-EE0005362; Australian Research Council; NASA's Arctic Boreal Vulnerability Experiment (ABoVE), Grant/Award Number: NNX15AV92A; Netherlands Organization for Scientific Research, Grant/Award Number: VIDI 864.10.006; BCC; NSF Award, Grant/Award Number: ABI-1458748; U.K. Department for Energy and Climate Change; ‘Juan de la Cierva ‐ Incorporación’ postdoctoral grant; Irish Research Council, Grant/Award Number: GOIPD/2015/81 ; DECC; Goethe International Postdoctoral Programme, People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007‐2013/ under REA grant agreement no [291776]; German Aerospace Center Award, Grant/Award Number: 50JR1601; Scottish Natural Heritage; Solway Coast AONB Sustainable Development Fund; COWRIE Ltd.; Heritage Lottery Fund; Robert Bosch Stiftung; NSF Division of Biological Infrastructure Award, Grant/Award Number: 1564380; Spanish Ministry of Economy and Competitiveness, Grant/Award Number: IJCI-2014-19190; Energinet.dk; NASA Award, Grant/Award Number: NNX15AV92A; MAVA Foundation; Fundação para a Ciência e Tecnologia, Grant/Award Number: SFRH/BPD/118635/2016; National Key R&D Program of China, Grant/Award Number: 2016YFC0500406; Green Fund of the Greek Ministry of Environment

Wing morphology is known to strongly affect flight performance by affecting lift and drag during flight. Performance may consequently deteriorate during feather moult due to the creation of feather gaps in the wing. Since wing gap size may directly affect the extent of reduced flight capacity, rapid moult involving the creation of large feather gaps is expected to substantially impair flight compared with the small gaps induced by a slower moult. To examine the factors affecting wing-feather moult speed, we studied adults of nineteen resident or very short-distance migrant passerine species during their post-breeding moult using a model-selection framework following a phylogenetically controlled analysis. We examined the speed of wing-feather moult in relation to each species’ flight distance index that was estimated based on local foraging movements rather than on longer flights (e.g., migration), assessed by the Delphi technique of expert evaluation. Moult speed was also examined with respect to six morphometric variables: body mass, wing loading, the feather comprising the tip of the wing, aspect ratio, wing span, and wing area. Our results suggest that flight distance index is the most important factor determining the speed of wing-feather moult in songbirds. Species that regularly fly a shorter distance were found to moult quickly, and those that take relatively longer flights moult slowly. These results suggest that the aerodynamic cost of wing area reduction due to feather moult shapes the evolution of annual routine processes by dictating a slower moult speed (resulting in small wing gaps) for species that regularly fly long distances and consequently may be affected more substantially by large wing gaps compared with short distance flyers.

Billions of migrating birds travel between their breeding and over-wintering areas twice a year, encountering various environmental conditions along their migration routes. Wind is of utmost importance for birds as wind speed and direction may strongly affect the birds’ flight speed and metabolism. Specifically, tailwinds were found to initiate flight and facilitate higher migration intensity and faster migratory movement while lowering the energetic cost of flight. Using radar, field observations and local meteorological measurements, we studied spring migrating raptors in a migration bottleneck in Italy near the Strait of Messina, between Sicily and Calabria. We explored the effects of wind on flight speed and the intensity of migration in soaring migrants. We found that the birds’ ground speed was positively affected by tailwind speed, and thus, tailwind likely allowed the birds to reach their destination faster. In addition, bird airspeed decreased under increasing tailwind speed, presumably lowering the energetic cost of flight. These findings are in line with predictions of optimal migration flight theory, yet, tailwind had an unexpected negative effect on migration intensity. We suggest that tailwind conditions induced a change in route selection by the migrants at a regional scale, causing a local decline in migration intensity. This change involves the undertaking of cross sea flight rather than overland detour. Furthermore, we found a modular response to crosswinds as birds compensated for winds blowing towards the sea and drifted when winds blew towards land. Our findings suggest that migrating raptors respond to en route wind conditions and coastline geography by adjusting several features of their flight in a manner that will increase their travel speed, reduce the energetic cost of flight, and permit a safe journey. Soaring birds exploit tailwinds to move faster and presumably to reduce the energetic cost of flight during migration. Using radar, we tested how bird flight is affected by tailwind and further predicted that the due to the advantages of using tailwinds, as increased number of birds migrating over the study area. We found that radar-tracked migrating birds flew faster with tailwinds over the study area, but despite this advantage, surprisingly low number of birds migrated when tailwinds prevailed. Furthermore, birds seem to drift with winds blowing from the sea to the land, but not in the opposite direction, suggesting that birds try to avoid drifting over the sea where it is riskier to fly. Hence, our study highlights the complexity of migrant flight behavior in relation to the wind and suggests a flexible response to different wind conditions and coastline geography at multiple spatiotemporal scales.

Made available in DSpace on 2018-11-26T17:44:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-26 Robert Bosch Foundation Animal movement is fundamental for ecosystem functioning and species survival, yet the effects of the anthropogenic footprint on animal movements have not been estimated across species. Using a unique GPS-tracking database of 803 individuals across 57 species, we found that movements of mammals in areas with a comparatively high human footprint were on average one-half to one-third the extent of their movements in areas with a low human footprint. We attribute this reduction to behavioral changes of individual animals and to the exclusion of species with long-range movements from areas with higher human impact. Global loss of vagility alters a key ecological trait of animals that affects not only population persistence but also ecosystem processes such as predator-prey interactions, nutrient cycling, and disease transmission. Senckenberg Gesell Naturforsch, Senckenberg Biodivers & Climate Res Ctr, D-60325 Frankfurt, Main, Germany Goethe Univ, Dept Biol Sci, D-60438 Frankfurt, Main, Germany Univ Maryland, Dept Biol, College Pk, MD 20742 USA Univ Maryland, SESYNC, Annapolis, MD 21401 USA Univ Guelph, Dept Integrat Biol, Guelph, ON N1G 2W1, Canada Norwegian Inst Nat Res, POB 5685 Torgard, NO-7485 Trondheim, Norway Duke Univ, Dept Biol, Durham, NC 27708 USA Duke Univ, Dept Evolut Anthropol, Durham, NC 27708 USA Hirola Conservat Programme, Garissa, Kenya Swedish Univ Agr Sci, Dept Wildlife Fish & Environm Studies, S-90183 Umea, Sweden Radboud Univ Nijmegen, Dept Anim Ecol & Physiol, Inst Water & Wetland Res, NL-6500 GL Nijmegen, Netherlands Univ Fed Mato Grosso do Sul, Ecol & Conservat Grad Program, Campo Grande, MS, Brazil Univ Alberta, Dept Biol Sci, Edmonton, AB, Canada Univ London, Royal Vet Coll, Struct & Motion Lab, London NW1 0TU, England Wildlife Conservat Soc, Mongolia Program, Ulaanbaatar, Mongol Peo Rep Mississippi State Univ, Forest & Wildlife Res Ctr, Carnivore Ecol Lab, Box 9690, Mississippi State, MS USA Sao Paulo State Univ, Anim Biol Postgra Program, BR-15054000 Sao Jose Do Rio Preto, SP, Brazil Michigan Dept Nat Resources, 1990 US 41 South, Marquette, MI 49855 USA Univ Calif Davis, Dept Anthropol, Davis, CA 95616 USA Aarhus Univ, Dept Biosci, DK-4000 Roskilde, Denmark Max Planck Inst Ornithol, Vogelwarte Radolfzell, D-78315 Radolfzell am Bodensee, Germany Wildlife Conservat Soc, Bronx, NY 10460 USA Univ Potsdam, Plant Ecol & Nat Conservat, D-14476 Potsdam, Germany Middle Tennessee State Univ, Dept Biol, Murfreesboro, TN 37132 USA Univ Pretoria, Dept Zool & Entomol, Mammal Res Inst, ZA-0028 Gauteng, South Africa Fdn Edmund Mach, Res & Innovat Ctr, Dept Biodivers & Mol Ecol, I-38010 San Michele All Adige, TN, Italy Harvard Univ, Dept Organism & Evolutionary Biol, Cambridge, MA 02138 USA Natl Zool Pk, Smithsonian Conservat Biol Inst, Front Royal, VA USA Univ Evora, Depat Fitotecn, P-7002554 Evora, Portugal Univ Evora, ICAAM, Inst Mediterranean Agr & Environm Sci, Evora, Portugal Univ Montpellier, Univ Paul Valery Montpellier, CNRS,EPHE, Ctr Ecol Fonctionnelle & Evolut,UMR 5175, F-34293 Montpellier 5, France Phillip Isl Nat Parks, Cowes, Vic, Australia Monash Univ, Sch Biol Sci, Melbourne, Vic, Australia Ohio State Univ, Dept Civil Environm & Geodet Engn, Columbus, OH 43210 USA Fiji Natl Univ, Dept Biol, POB 5529, Natabua, Lautoka, Fiji Univ Massachusetts, US Geol Survey, Massachusetts Cooperat Fish & Wildlife Res Unit, Amherst, MA 01003 USA Penn State Univ, US Geol Survey, Penn Cooperat Fish & Wildlife Res Unit, University Pk, PA 16802 USA Univ Oxford, Dept Zool, Oxford OX1 3PS, England Giraffe Conservat Fdn, POB 86099, Eros, Namibia German Primate Ctr, Behav Ecol & Sociobiol Unit, D-37077 Gottingen, Germany Tech Univ Munich, Dept Ecol & Ecosyst Management, Restorat Ecol, D-85354 Freising Weihenstephan, Germany Cary Inst Ecosyst Studies, Millbrook, NY 12545 USA Univ British Columbia, Irving K Barber Sch Arts & Sci, Unit 2, Biol, Okanagan Campus, Kelowna, BC V1V 1V7, Canada Univ Zurich, Dept Evolutionary Biol & Environm Studies, CH-8057 Zurich, Switzerland Univ Wyoming, Dept Zool & Physiol, Laramie, WY 82071 USA Univ Washington, Sch Environm & Forest Sci, Seattle, WA 98195 USA Univ Montana, Coll Forestry & Conservat, Dept Ecosyst & Conservat Sci, Wildlife Biol Program, Missoula, MT 59812 USA Bavarian Forest Natl Pk, Dept Conservat & Res, D-94481 Grafenau, Germany Albert Ludwigs Univ Freiburg, Wildlife Ecol & Management, D-79106 Freiburg, Germany Univ Toulouse, INRA, CEFS, Castanet Tolosan, France Univ Calif Davis, Anim Behav Grad Grp, Davis, CA 95616 USA Bionet Natr Onderzoek, NL-6171 EL Stein, Netherlands Univ Vet Med Vienna, Res Inst Wildlife Ecol, A-1160 Vienna, Austria Univ Coll Cork, Sch Biol Earth & Environm Sci, Cork, Ireland Univ Wyoming, US Geol Survey, Dept Zool & Physiol, Wyoming Cooperat Fish & Wildlife Res Unit, Laramie, WY USA North Carolina Museum Nat Sci, Raleigh, NC 27601 USA North Carolina State Univ, Dept Forestry & Environm Resources, Raleigh, NC 27695 USA Karatina Univ, Dept Nat Resource Management, POB 195710101, Karatina, Kenya Univ Lethbridge, Dept Psychol, Lethbridge, AB T1K 3M4, Canada Columbia Univ, Lamont Doherty Earth Observ, Palisades, NY 10964 USA Univ Valencia, Terr Vertebrates Grp, Cavanilles Inst Biodivers & Evolutionary Biol, E-46980 Valencia, Spain SUNY Stony Brook, Dept Anthropol, Stony Brook, NY 11794 USA TSG, SSC, IUCN, Rua Licuala 622,Damha 1,Campo Grande, BR-79046150 Mato Grosso Sul, Brazil IPE Inst Pesquisas Ecol Inst Ecol Res, Caixa Postal 47, BR-12960000 Sao Paulo, Brazil Univ Alicante, Dept Ciencias Ambient & Recursos Natur, Vertebrates Zool Res Grp, Alicante, Spain Embrapa Pantanal, BR-79320900 Corumba, MS, Brazil Chico Mendes Inst Conservat Biodivers, Natl Res Ctr Carnivores Conservat, BR-12952011 Atiba, SP, Brazil Univ Glasgow, Inst Biodivers Anim Hlth & Comparat Med, Glasgow, Lanark, Scotland NYU, Dept Biol, Ctr Genom & Syst Biol, New York, NY 10003 USA Univ Calif Davis, Dept Microbiol & Mol Genet, Davis, CA 95616 USA Univ Oslo, Dept Biosci, Ctr Ecol & Evolutionary Synth, NO-0316 Oslo, Norway Hebrew Univ Jerusalem, Alexander Silberman Inst Life Sci, Dept Ecol Evolut & Behav, Movement Ecol Lab, IL-91904 Jerusalem, Israel Norwegian Inst Nat Res, NO-0349 Oslo, Norway Norwegian Univ Sci & Technol NTNU, Dept Math Sci & Ctr Biodivers Dynam, N-7491 Trondheim, Norway Univ Fed Mato Grosso do Sul, Dept Ecol, BR-79070900 Campo Grande, MS, Brazil Field Museum Nat Hist, Integrat Res Ctr, Chicago, IL 60605 USA Consorzio Parco Nazl Stelvio, Bormio, Sondrio, Italy Univ Grenoble Alpes, Irstea, UR LESSEM, BP 76, F-38402 St Martin Dheres, France Univ Bayreuth, BayCEER, D-95447 Bayreuth, Germany Natl Park Schwarzwald, D-77889 Seebach, Germany Univ New South Wales, Evolut & Ecol Res Ctr, Sydney, NSW 2052, Australia Univ New South Wales, Sch Biol Earth & Environm Sci, Sydney, NSW 2052, Australia Penn Game Commiss, Harrisburg, PA 17110 USA Princeton Univ, Dept Ecol & Evolutionary Biol, Princeton, NJ 08544 USA Univ Konstanz, Dept Biol, D-78467 Constance, Germany Off Natl Chasse & Faune Sauvage, Studies & Expertise DRE, F-01330 Birieux, France Univ Haifa, Dept Evolutionary & Environm Biol, IL-3498838 Haifa, Israel Western Ecosyst Technol Inc, Laramie, WY 82070 USA Aarhus Univ, Arctic Res Ctr, DK-8000 Aarhus C, Denmark Polish Acad Sci, Inst Nat Conservat, PL-31120 Krakow, Poland Univ Porto, CIBIO InBIO Associate Lab, P-4485661 Vairao, Portugal Univ Lisbon, Inst Super Agron, InBIO Associate Lab, Ctr Appl Ecol Prof Baeta Neves, P-1349017 Lisbon, Portugal Univ Lisbon, Fac Ciencias, Ctr Ecol Evolut & Environm Changes, P-1749016 Lisbon, Portugal Univ Calif Davis, Dept Environm Sci & Policy, Davis, CA 95616 USA Jackson Hole Conservat, Jackson, WY 83001 USA Univ Vet Med Hannover, Inst Terr & Aquat Wildlife Res, D-30173 Hannover, Germany Univ Calif Santa Cruz, Environm Studies Dept, Ctr Integrated Spatial Res, Santa Cruz, CA 95060 USA Univ Pretoria, Dept Zool & Entomol, ZA-0028 Hatfield, South Africa Colorado State Univ, Dept Fish Wildlife & Conservat Biol, Ft Collins, CO 80523 USA Tatra Natl Pk, PL-34500 Zakopane, Poland Sao Paulo State Univ, Anim Biol Postgra Program, BR-15054000 Sao Jose Do Rio Preto, SP, Brazil

Although feathers are the unifying characteristic of all birds, our understanding of the causes, mechanisms, patterns and consequences of the feather moult process lags behind that of other major avian life-history phenomena such as reproduction and long-distance migration. Migration, which evolved in many species of the temperate and arctic zones, requires high energy expenditure to endure long-distance journeys. About a third of Western-Palearctic passerines perform long-distance migrations of thousands of kilometres each year using various morphological, physiological, biomechanical, behavioural and life-history adaptations. The need to include the largely non-overlapping breeding, long-distance migration and feather moult processes within the annual cycle imposes a substantial constraint on the time over which the moult process can take place. Here, we review four feather-moult-related adaptations which, likely due to time constraints, evolved among long-distance Western-Palearctic migrants: (i) increased moult speed; (ii) increased overlap between moult and breeding or migration; (iii) decreased extent of plumage moult; and (iv) moult of part or all of the plumage during the over-wintering period in the tropics rather than in the breeding areas. We suggest that long-distance migration shaped the evolution of moult strategies and increased the diversity of these strategies among migratory passerines. In contrast to this variation, all resident passerines in the Western Palearctic moult immediately after breeding by renewing the entire plumage of adults and in some species also juveniles, while in other species juvenile moult is partial. We identify important gaps in our current understanding of the moult process that should be addressed in the future. Notably, previous studies suggested that the ancestral moult strategy is a post-breeding summer moult in the Western Palearctic breeding areas and that moult during the winter evolved due to the scheduling of long-distance migration immediately after breeding. We offer an alternative hypothesis based on the notion of southern ancestry, proposing that the ancestral moult strategy was a complete moult during the 'northern winter' in the Afro-tropical region in these species, for both adults and juveniles. An important aspect of the observed variation in moult strategies relates to their control mechanisms and we suggest that there is insufficient knowledge regarding the physiological mechanisms that are involved, and whether they are genetically fixed or shaped by environmental factors. Finally, research effort is needed on how global climate changes may influence avian annual routines by altering the scheduling of major processes such as long-distance migration and feather moult.

Different weather conditions are known to affect bird migration, yet the influence of fog and low clouds on migrating birds has been rarely examined so far, and hence, their impact on bird movement is not well understood. Fog avoidance could be a consequence of visual limitations within the fog or may be the outcome of deteriorated soaring conditions due to the obstruction of the sun. We carried out a radar study at the Strait of Messina, which is a bottleneck for migrating birds traversing the Central Mediterranean Sea, to determine if the intensity of diurnal soaring bird migration was influenced by fog and other weather variables. We recorded bird movements using an X-band radar, which can detect birds flying within the fog, and recorded weather conditions using local meteorological observations. We examined if bird passage rate (number of tracks/hour) at the radar site was influenced by fog, wind speed and direction, air temperature and the time of day. Our findings suggest that fog was the most important factor affecting bird migration intensity as recorded by the radar, indicating that birds actively avoided flying into fog. In addition, wind direction affected bird migration intensity, with lower numbers recorded with southerly tailwinds and higher numbers recorded with westerly crosswinds. Our findings highlight a consequence of widespread meteorological conditions, and of fog in particular, on migrating birds, with implications for bird migration navigation, path length and flight energetics.

Migratory animals provide a multitude of services and disservices—with benefits or costs in the order of billions of dollars annually. Monitoring, quantifying, and forecasting migrations across continents could assist diverse stakeholders in utilizing migrant services, reducing disservices, or mitigating human–wildlife conflicts. Radars are powerful tools for such monitoring as they can assess directional intensities, such as migration traffic rates, and biomass transported. Currently, however, most radar applications are local or small scale and therefore substantially limited in their ability to address large-scale phenomena. As weather radars are organized into continent-wide networks and also detect “biological targets,” they could routinely monitor aerial migrations over the relevant spatial scales and over the timescales required for detecting responses to environmental perturbations. To tap these unexploited resources, a concerted effort is needed among diverse fields of expertise and among stakeholders to recognize the value of the existing infrastructure and data beyond weather forecasting.