Revealing patterns of nocturnal migration using the European weather radar network

Nilsson, Cecilia; Dokter, Adriaan M.; Verlinden, Liesbeth; Shamoun-Baranes, Judy; Schmid, Baptiste; Desmet, Peter; Bauer, Silke; Chapman, Jason W.; Alves, José A.; Stepanian, Phillip M.; Sapir, Nir; Wainwright, Charlotte E.; Boos, Mathieu; Górska, Anna; Menz, Myles H. M.; Rodrigues, Pedro; Leijnse, H.; Zehtindjiev, Pavel; Brabant, R.; Haase, Günther; Weisshaupt, Nadja; Ciach, Michał; Liechti, Félix

doi:10.1111/ecog.04003

Cited by 76 publications

(123 citation statements)

References 55 publications

(105 reference statements)

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“…Using information regarding current and expected atmospheric conditions when deciding to depart or land may increase survival and the chance to land in a suitable area while decreasing the animal's metabolic cost of transport. Wind speed and direction have pronounced effects on migratory departure and landing in insects and birds, and consequently these may affect the intensity of migration aloft (Rose et al 1985, Dokter et al 2011, Chapman et al 2015a, chapter 11 in Drake and Reynolds 2012, Hu et al 2016, Nilsson et al 2019.…”

Section: Atmospheric Conditionsmentioning

confidence: 99%

“…Recently, weather radar networks in Europe and the USA have been successfully applied to study the broad front migration of birds, of which most are songbirds (Dokter et al 2018, Van Doren and Horton 2018, Nilsson et al 2019. The application of algorithms to study the movement of birds that congregate in flocks during migration, including waterbirds (e.g.…”

Section: Identifying and Tracking Of Additional Taxa By Radarsmentioning

confidence: 99%

“…NEXRAD) and Europe (i.e. OPERA), which successfully monitor mass movements of aerial organisms over regional (Dokter et al 2011, Farnsworth et al 2016, Hu et al 2016) and continental scales (Lowery and Newman 1966, Van Doren and Horton 2018, Nilsson et al 2019), the scarcity of radar studies from the African continent, most of Asia and South America limits our knowledge of animal aeroecology in these vast areas. The development of processing and analytical methodologies, as well as knowledge sharing and inter-disciplinary data integration for identifying and tracking aerial migrants across Europe was conducted by the COST (European Cooperation in Science and Technology) action ENRAM (European Network for the Radar surveillance of Animal Movement in Europe; <www.enram.eu>) during 2013-2017.…”

Section: Increasing the Coverage Of Aeroecological Radar Studiesmentioning

confidence: 99%

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Environmental effects on flying migrants revealed by radar

et al. 2019

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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 visibility conditions. We review how atmospheric conditions, geographic features and human development affect the behavior of migrating insects and birds as recorded by radars. We focus on flight initiation and termination, as well as in‐flight behavior that includes changes in animal flight direction, speed and altitude. We have identified several similarities and differences in the behavioral responses of aerial migrants including an overlooked similarity in the use of thermal updrafts by very small (e.g. aphids) and very large (e.g. vultures) migrants. We propose that many aerial migrants modulate their migratory flights in relation to the interaction between atmospheric conditions and geographic features. For example, aerial migrants that encounter crosswind may terminate their flight or continue their migration and may also drift or compensate for lateral displacement depending on their position (over land, near the coast or over sea). We propose several promising directions for future research, including the development and application of algorithms for tracking insects, bats and large aggregations of animals using weather radars. Additionally, an important contribution will be the spatial expansion of aeroecological radar studies to Africa, most of Asia and South America where no such studies have been undertaken. Quantifying the role of migrants in ecosystems and specifically estimating the number of departing birds from stopover sites using low‐elevation radar scans is important for quantifying migrant–habitat relationships. This information, together with estimates of population demographics and migrant abundance, can help resolve the long‐term dynamics of migrant populations facing large‐scale environmental changes.

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Section: Atmospheric Conditionsmentioning

confidence: 99%

Section: Identifying and Tracking Of Additional Taxa By Radarsmentioning

confidence: 99%

Section: Increasing the Coverage Of Aeroecological Radar Studiesmentioning

confidence: 99%

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Environmental effects on flying migrants revealed by radar

et al. 2019

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“…There are several methods to monitor the movements of animals in the airspace (Drake and Bruderer 2017), with radar being the predominant technology when it comes to quantifying biomass flows (Chilson et al 2017). Radar systems provide an ideal tool to monitor the temporal and spatial patterns of animal movements locally (Bruderer 1997, Fijn et al 2015, Hu et al 2016, Nilsson et al 2018, as well as on a large scale (Gauthreaux et al 2003, Chilson et al 2012, Dokter et al 2018, van Doren and Horton 2018, Nilsson et al 2019. Therefore, the significance and demand for quantitative radar studies of animal movements in the context of ecological or environmental impact assessment studies has increased considerably (Bridge et al 2011, Bauer and Hoye 2014, Bauer et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Size matters in quantitative radar monitoring of animal migration: estimating monitored volume from wingbeat frequency

et al. 2019

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Quantitative radar studies are an important component of studying the movements of birds. Whether a bird, at a certain distance from the radar, is detected or not depends on its size. The volume monitored by the radar is therefore different for birds of different sizes. Consequently, an accurate quantification of bird movements recorded by small‐scale radar requires an accurate determination of the monitored volume for the objects in question, although this has tended to be ignored. Here, we demonstrate the importance of sensitivity settings for echo detection on the estimated movement intensities of birds of different sizes. The amount of energy reflected from a bird and detected by the radar receiver (echo power) depends not only on the bird's size and on the distance from the radar antenna, but also on the beam shape and the bird's position within this beam. We propose a method to estimate the size of a bird based on the wingbeat frequency, retrieved from the echo‐signal, independent of the absolute echo power. The estimated bird‐size allows calculation of size‐specific monitored volumes, allowing accurate quantification of movement intensities. We further investigate the importance of applying size‐specific monitored volumes to quantify avian movements instead of using echo counts. We also highlight the importance of accounting for size‐specific monitored volume of small scale radar systems, and the necessity of reporting technical information on radar parameters. Applying this framework will increase the quality and validity of quantitative radar monitoring.

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“…Second, studying birth and death rates is difficult because conditions experienced during one annual stage may have delayed fitness consequences that appear in a subsequent stage (Senner et al 2015). This limitation is overcome by large-scale and long-term weather surveillance radar networks (Kelly and Horton 2016, Van Doren and Horton 2018, Nilsson et al 2019 (Fig. the monarch butterfly Danaus plexippus (Inamine et al 2016)).…”

Section: News and Viewsmentioning

confidence: 99%

Radar aeroecology – a missing piece of the puzzle for studying the migration ecology of animals

Schmaljohann

2019

Ecography

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In a recent Ecography article, Bauer et al. (2019) identified the most pressing questions for advancing our understanding of how anthropogenic changes in the environment affect aerial migrants at the macroscale and how these changes consequently influence humans. To surmount the associated challenges, large-scale networks of weather surveillance radar are the suggested solution because addition to measuring precipitation and wind, they also continuously monitor the aggregated biomass movements of insects, birds and bats over large spatial and temporal scales. As such, they provide essential and unprecedented fundamental information about macroecological patterns (e.g. migration routes, phenologies and navigation strategies) for migratory species. In addition to the simultaneous description of such patterns for all such species at the continental level, long-term changes in these can be revealed by taking into account existing historical radar data. The combination of these three properties, i.e. cross-species, continental and long-term, is unique and provides the much-needed information regarding migration ecology that the individual-based approaches cannot provide via tracking, manipulative and genetic studies of single species. Thus, radar aeroecology constitutes a missing piece of the puzzle to answer the grand challenges of migration ecology.'One swallow does not make a spring'. This Greek proverb means that one should not jump to conclusions based on a single positive event. For example, a swallow arriving at its breeding area does not yet announce the beginning of spring. It also applies to many other migrants (e.g. butterflies, salmon, geese, shorebirds, bats and whales) showing different environmentally induced migratory syndromes (e.g. latitudinal, altitudinal, seasonal and irruptive movements). The comings and goings of migrants intensify our perception of the changing seasons and have emotional value. Due to the worldwide decline in abundance of migrants (Wilcove and Wikelski 2008), humans in many parts of the world are paying increased attention to environmental changes affecting such charismatic species.The factors affecting migratory animals is not only an emotionally but also economically important question because especially airborne migrants perform important ecosystem services (e.g. pollination of crops, pest control and biomass production)

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Revealing patterns of nocturnal migration using the European weather radar network

Cited by 76 publications

References 55 publications

Environmental effects on flying migrants revealed by radar

Environmental effects on flying migrants revealed by radar

Size matters in quantitative radar monitoring of animal migration: estimating monitored volume from wingbeat frequency

Radar aeroecology – a missing piece of the puzzle for studying the migration ecology of animals

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