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Radar ornithology

Radar is the only technology which allows recording bird migration continuously over long time periods and across all height intervals during day and night. The Swiss Ornithological Institute has been investigating bird migration by radar for more than 40 years. Various studies have been carried out in Europe, the Near East and the Africa. Apart from basic research, studies with respect to environmental impact assessments have been an important part of the work (e.g. impact of wind farms, tall buildings, etc.).


Our radar studies aim at:

  • investigating the environmental influence on the temporal and spatial distribution of bird migration
  • examining the environmental influence on individual flight behaviour
  • modelling and forecasting the temporal and spatial phenology of bird migration
  • improving radar systems for automatic real-time recording and analysis of bird migration
  • improving software for automatic classification and identification of different species or groups of species (e.g. passerines, waterfowl).


The airspace is being used by a large variety of avian and non-avian species. Therefore, differentiating between birds and non-bird echoes (e.g. insects, rain, ground clutter) is essential. We monitor bird movements at specific locations with radar systems specifically developed to record and identify birds (BirdScan MR1).

These systems allow . . .

  • a continuous quantitative compilation of height distributions
  • the recording of flight directions and flight speeds
  • the identification of different groups of birds based on their wing-beat patterns

Within an international cooperation we could show that weather radars can be well suited to provide highly valuable information on bird migration. As a follow-up, we now cooperate within the European network of Radar Animal Monitoring (ENRAM) with colleagues from all around the world to make use of the European network of weather radars for a large-scale monitoring of bird movements across the European continent.


Quantifying the spatially and temporally explicit patterns of bird movements is a prerequisite to understand environmental impacts on the continent-wide migration. Only a continuous and automatic monitoring of migration by radar allows systematically recording also the rare but very specific events of mass movements, which often are only mentioned as anecdotes. Modelling and forecasting bird movements are not only important for basic research, but are also highly welcome for avoiding collision in military and civil aviation as well as at tall man-made constructions.


  • Influence of topographical structures (mountain ranges, sea, desert) on migratory behaviour of trans-Sahara migrants
  • Height distributions of migrants in relation to atmospheric conditions (wind etc.)
  • Validation of weather radar systems for quantifying nocturnal bird migration
  • Validation of capture numbers (bird ringing) in relation to migratory intensity
  • Potential hazard for migratory birds by wind turbines and other tall buildings
  • Composition of nocturnal bird migration (passerines, waterfowl)
  • Flight speed, air speed and wing-beat patterns of wild birds

Project management

Felix Liechti, Janine Aschwanden, Thomas Steuri, Baptiste Schmid


Financial support

SNF – Swiss National science Foundation


Aschwanden, J., M. Schmidt, G. Wichmann, H. Stark, D. Peter, T. Steuri & F. Liechti (2020):
Barrier effects of mountain ranges for broad‑front bird migration. test
Aurbach, A., B. Schmid, F. Liechti, N. Chokani & R. Abhari (2020):
Simulation of broad front bird migration across Western Europe. test
Bauer, S., J. Shamoun-Baranes, C. Nilsson, A. Farnsworth, J. Kelly, D. Reynolds, A. Dokter, J. Krauel, L. Petterson, K. Horton & J. Chapman (2019):
The grand challenges of migration ecology that radar aeroecology can help answer test
Liechti, F., J. Aschwanden, J. Blew, M. Boos, R. Brabant, A. Dokter, V. Kosarev, M. Lukach, M. Maruri, M. Reyniers, I. Schekler, H. Schmaljohann, B. Schmid, N. Weisshaupt & N. Sapir (2019):
Cross‐calibration of different radar systems for monitoring nocturnal bird migration across Europe and the Near East test
Nussbaumer, R., L. Benoit, G. Mariethoz, F. Liechti, S. Bauer & B. Schmid (2019):
A Geostatistical Approach to Estimate High Resolution Nocturnal Bird Migration Densities from a Weather Radar Network test
Schmid, B., S. Zaugg, S. Votier, J. Chapman, M. Boos & F. Liechti (2019):
Size matters in quantitative radar monitoring of animal migration: estimating monitored volume from wingbeat frequency test
Tschanz, P.; L. Pellissier, X. Shi, F. Liechti & B. Schmid (2019):
Consistency of spatio-temporal patterns of avian migration across the Swiss lowlands. test
Aschwanden, J., H. Stark, D. Peter, T. Steuri, B. Schmid & F. Liechti (2018):
Bird collisions at wind turbines in a mountainous area related to bird movement intensities measured by radar. test
Bruderer, B., D. Peter & F. Korner-Nievergelt (2018):
Vertical distribution of bird migration between the Baltic Sea and the Sahara. test
Nilsson, C., A. M. Dokter, B. Schmid, M. Scacco, L. Verlinden, J. Bäckman, G. Haase, G. Dell’Omo, J. W. Chapman, H. Leijnse & F. Liechti (2018):
Field validation of radar systems for monitoring bird migration. test
Alistair V. D. & B. Bruderer (2017):
Aeroecological Observation Methods. test
Chilson, P. B., W. F. Frick, J. F. Kelly & F. Liechti (2017):
Aeroecology. test
Liechti F. & L. P. McGuire (2017):
Facing the Wind: The Aeroecology of Vertebrate Migrants. test
Schmidt, M., J. Aschwanden, F. Liechti, G. Wichmann & E. Nemeth (2017):
Comparison of visual bird migration counts with radar estimates. test
Shamoun-Baranes, J., F. Liechti & W. M. G. Vansteelant (2017):
Atmospheric conditions create freeways, detours and tailbacks for migrating birds. test
Horvitz, N., N. Sapir, F. Liechti, R. Avissar, I. Mahrer & R. Nathan (2014):
The gliding speed of migrating birds: slow and safe or fast and risky? test
Shamoun-Baranes, J., J.A. Alves, S. Bauer, A.M. Dokter, O. Hüppop, J. Koistinen, H. Leijnse, F. Liechti, H. van Gasteren & J.W. Chapman (2014):
Continental-scale radar monitoring of the aerial movements of animals. test
Bruderer, B., T. Steuri, J. Aschwanden & F. Liechti (2012):
Vom militärischen Zielfolgeradar zum Vogelradar. test
Stefanescu, C., F. Páramo, S. Åkesson, M. Alarcón, A. Ávila, T. Brereton, J. Carnicer, L. F. Cassar, R. Fox, J. Heliölä, J. K. Hill, N. Hirneisen, N. Kjellén, E. Kühn, M. Kuussaari, M. Leskinen, F. Liechti, M. Musche, E. C. Regan, D. R. Reynolds, D. B. Roy, N. Ryrholm, H. Schmaljohann, J. Settele, C. D. Thomas, C. van Swaay & J. W. Chapman (2012):
Multi-generational long-distance migration of insects: studying the painted lady butterfly in the Western Palaearctic. test
Bruderer, B., D. Peter, A. Boldt & F. Liechti (2010):
Wing-beat characteristics of birds recorded with tracking radar and cine camera. test