Nir Sapir

University of Haifa | haifa · Department of Evolutionary and Environmental Biology

Optimal foraging theory posits that foragers adjust their movements based on prey abundance to optimize food intake. While extensively studied in terrestrial and marine environments, aerial foraging has remained relatively unexplored due to technological limitations. This study, uniquely combining BirdScan-MR1 radar and the ATLAS biotelemetry syste...

A major problem in studying bird movement in many countries is data scarcity, precluding information about the spatial and temporal properties of avian distribution and dynamics as well as their consequences for human lives. We address this problem by proposing an innovative approach based on the relation between counts of signal attenuation of wir...

During spring migration, nocturnal migrants attempt to minimize their travel time to reach their breeding grounds early. However, how they behave and respond to unfavourable conditions during their springtime travels is much less understood. In this study, we reveal the effects of atmospheric factors on nocturnal bird migration under adverse condit...

Optimal foraging theory posits that foragers adjust their movements based on prey abundance to optimize food intake. While extensively studied in terrestrial and marine environments, aerial foraging has remained relatively unexplored due to technological limitations. This study, uniquely combining BirdScan-MR1 radar and the ATLAS biotelemetry syste...

Optimal foraging theory posits that foragers adjust their movements based on prey abundance to optimize food intake. While extensively studied in terrestrial and marine environments, aerial foraging has remained relatively unexplored due to technological limitations. This study, uniquely combining BirdScan-MR1 radar and the ATLAS biotelemetry syste...

Challenges imposed by geographical barriers during migration are selective agents for animals. Juvenile soaring landbirds often cross large water bodies along their migratory path, where they lack updraft support and are vulnerable to harsh weather. However, the consequences of inexperience in accomplishing these water crossings remain largely unqu...

Assessing habitat quality is critical for migrating birds, with implications for fuel loading, predation risk and timing of departure. To efficiently distribute within stopover sites, migrants rely on various cues that facilitate habitat quality assessment. In this study, we conducted a playback experiment at a mid‐route stopover site to test the e...

Human-induced direct mortality affects huge numbers of birds each year, threatening hundreds of species worldwide. Tracking technologies can be an important tool to investigate temporal and spatial patterns of bird mortality as well as their drivers. We compiled 1704 mortality records from tracking studies across the African-Eurasian flyway for 45...

Numerous Woodchat Shrike ( Lanius senator ) populations, and Laniidae in general, are globally declining. A deeper understanding of their breeding ecology, including their nest-site selection and breeding performance, from hatching success to post-fledging survival, could contribute to their conservation. We studied breeding Woodchat Shrikes near t...

Many vulture populations have severely declined in the past decades, showing high juvenile mortality. To support these populations, feeding stations are used to increase food availability and to supply food without antibiotics and toxic compounds. Yet, supplying food at feeding stations may affect vulture behavior. We present a large-scale field ex...

Optimal foraging theory posits that foragers adjust their movements based on prey abundance to optimize food intake. While extensively studied in terrestrial and marine environments, aerial foraging has remained relatively unexplored due to technological limitations. This study, uniquely combining BirdScan-MR1 radar and the ATLAS biotelemetry syste...

The Bonelli’s Eagle (Aquila fasciata) is a critically endangered species in Israel, with electrocution on power lines posing a serious threat to its population. Because retrofitting of electricity pylons to prevent mortality is a slow and costly process, it is important to prioritize the pylons in the network for quick and efficient mitigation of e...

The Bonelli’s Eagle ( Aquila fasciata ) is a critically endangered species in Israel, with electrocution on power lines posing a serious threat on its population. Since insulation of electricity pylons is a slow and costly process, it is important to prioritize the insulation of the pylons in the network for quick and efficient mitigation of eagle...

Background 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...

Describing animal space use is essential for understanding their ecological needs and for planning effective conservation schemes. Notably, certain biomes and life histories are understudied due to methodological challenges in tracking animals in their natural habitats. Specifically, both arid environments and nocturnal species are not sufficiently...

The use of weather radars to detect and distinguish between different biological patterns greatly improves our understanding of aeroecology and its consequences for our lives. Importantly, it allows us to quantify passerine bird migration at different scales. Yet, no algorithm to detect soaring bird flocks in weather radar is available, precluding...

Bat movement and behaviour are still mostly understudied over large scales. High‐altitude, nocturnal activity makes visual identification of bats from the ground virtually impossible, dramatically hindering our ability to study their movement ecology. Despite the wide use of radar in aeroecology, its application to study specific taxa is limited du...

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 percnopter...

Plumage colouration and moult extent: males set the fashion and females pay the price

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 directl...

Wind energy is a major and rapidly expanding renewable energy source. Horizontal‐axis wind turbines, the main tool in this industry, induce mortality in flying animals and consequently bring about conservation concerns and regulatory restrictions. We utilized a unique combination of RADAR, LIDAR and ultrasonic acoustic recorders to test the utility...

Fuel deposition rate is predicted to determine departure fuel load during stopover in two models of optimal behavior of migrating birds. Yet, near ecological barriers, such as wide deserts, birds may switch to a different strategy of departing with just enough fuel to enable the long cross-barrier flight, thus reaching a threshold of fuel load rega...

Background Various mammalian species emit ultrasonic vocalizations (USVs), which reflect their emotional state and mediate social interactions. USVs are usually analyzed by manual or semi-automated methodologies that categorize discrete USVs according to their structure in the frequency-time domains. This laborious analysis hinders the effective us...

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.

Stopping-over is critical for migrating birds. Yet, our knowledge of bird stopover distributions and their mechanisms near wide ecological barriers is limited. Using low elevation scans of three weather radars covering 81,343 km², we quantified large-scale bird departure patterns during spring and autumn (2014–2018) in between two major ecological...

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, s...

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 the...

With emerging technologies such as the 5G and IoT, wireless communication has become more and more dominant in human life. Many applications require high quality of service (QoS) and even momentarily interruption may cause irreversible damage. The signal level in wireless point-to-point communication links is affected by environmental phenomena, in...

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....

This repository contains the reference dataset of labelled (or otherwise useful) echo samples acquired with a BirdScan MR1 radar. This dataset enables classification of the radar echoes acquired with a BirdScan MR1 into a number of biological groups of interests (as well as the removal of non-biological targets). Follow the DOI link for more info...

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 spec...

Atmospheric conditions are known to affect flight propensity, behaviour during flight, and migration route in birds. Yet, the effects of fog have only rarely been studied although they could disrupt orientation and hamper flight. Fog could limit the visibility of migrating birds such that they might not be able to detect landmarks that guide them d...

Migratory connectivity of Steppe Eagles Introduction The steppe eagle Aquila nipalensis is an Endangered large raptor, that breeds in Eurasian steppe. Despite its wide distribution and charismatic appearance, much is still unknown about its ecology, behavior and migration. We used data from GPS-tracked steppe eagles to map migration and to calcu...

Migratory birds are often not specifically adapted to arid conditions, yet several species travel across deserts during their journeys, and often have more or less short stopovers there. We investigated whether differences in thermoregulatory mechanisms, specifically evaporative cooling, explain the different behavior of three passerine species whi...

Atmospheric conditions are known to affect flight propensity, behaviour during flight, and migration route in birds. Yet, the effects of fog have only rarely been studied although they could disrupt orientation and hamper flight. Fog could limit the visibility of migrating birds such that they might not be able to detect landmarks that guide them d...

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 fligh...

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...

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...

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...

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 throug...

Feather molt is an important life-history process in birds, but little is known about its evolutionary history. Here, we report on the first fossilized evidence of sequential wing feather molt, a common strategy among extant birds, identified in the Early Cretaceous four-winged dromaeosaurid Microraptor. Analysis of wing feather molt patterns and e...

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 b...

Supporting information to the article: "Causes and consequences of facultative sea crossing in a soaring migrant"

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...

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 mont...

Many insectivorous passerines become frugivorous during migration. Because water may facilitate the digestion of dry fruits, some passerines may benefit from staging in stopover sites that offer access to drinking water. In autumn, water consumption by Blackcaps (Sylvia atricapilla) staging in Israel was found to induce a shift from insectivory to...

Migratory animals are affected by various factors during their journeys, and the study of animal movement by radars has been instrumental in revealing key influences of the environment on flying migrants. Radars enable the simultaneous tracking of many individuals of almost all sizes within the radar range during day and night, and under low visibi...

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 conditio...

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...

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 dif...

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 ext...

Resource allocation for body tissues is under strong selection pressures because allocating too many resources may waste both energy and essential nutrients, and allocating too few resources can result in functional disability. We thus hypothesized that feather quality is the outcome of life-history trade-offs that determine feather resource alloca...

Early arrival at breeding grounds is of prime importance for migrating birds as it is known to enhance breeding success. Adults, males and higher quality individuals typically arrive earlier, and across years, early arrival has been linked to warmer spring temperatures. However, the mechanisms and potential costs of early arrival are not well under...

Biotelemetry is increasingly used to study animal movement at high spatial and temporal resolution and guide conservation and resource management. Yet, limited sample sizes and variation in space and habitat use across regions and life stages may compromise robustness of behavioral analyses and subsequent conservation plans. Here, we assessed varia...

Biotelemetry is increasingly used to study animal movement at high spatial and temporal resolution and guide conservation and resource management. Yet, limited sample sizes and variation in space and habitat use across regions and life stages may compromise robustness of behavioral analyses and subsequent conservation plans. Here, we assessed varia...

Chapman, J., Shamoun-Baranes, J., Dokter, A., Leijnse, H., Liechti, F., Koistinen, J., Nilsson, C., van Gasteren, H., Alves, J., Sapir, N., Hüppop, O., Reynolds, D. & Bauer, S. (2018) The European Network for the Radar surveillance of Animal Movement (ENRAM). Presentation EGU2018-12875 at European Geosciences Union General Assembly 2018, Vienna, A...

Birds usually moult their feathers in a particular sequence which may incur aerodynamic, physiological and behavioural implications. Among birds, hummingbirds are unique species in their sustained hovering flight. Because hummingbirds frequently hover-feed, they must maintain sufficiently high flight capacities even when moulting their flight feath...

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 fli...

Restrictions on roaming Until the past century or so, the movement of wild animals was relatively unrestricted, and their travels contributed substantially to ecological processes. As humans have increasingly altered natural habitats, natural animal movements have been restricted. Tucker et al. examined GPS locations for more than 50 species. In ge...

Desert Owl Strix hadorami (hereafter hadorami; formerly Hume’s Owl or Hume’s Tawny Owl) has recently been renamed after papers published by Robb et al (2013, 2016) and Kirwan et al (2015), backed up by taxonomic research by Kirwan et al (2015) and Robb et al (2016). Following the taxonomic developments and especially the renaming of hadorami, an we...

Background: The Western Marsh Harrier (Circus aeruginosus) is a partial migrant with the populations from Eastern and Northern Europe migrating south to sub-Saharan Africa. During the autumn migration, that is peaking in September, harriers move on a broad front heading SW and undertake long sea-crossings en route to their wintering quarters, passi...

The diverse hummingbird family (Trochilidae) has unique adaptations for nectarivory, among which is the ability to sustain hover-feeding. As hummingbirds mainly feed while hovering, it is crucial to maintain this ability throughout the annual cycle—especially during flight-feather moult, in which wing area is reduced. To quantify the aerodynamic ch...