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
    • modeling 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. Depending on the research question, we use different radar systems.

    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
    • tracking of selected individuals over several kilometres.

    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 EU COST-Action 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.


    B: 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, Herbert Stark, Thomas Steuri


    Prof. Bruno Bruderer
    ENRAM – European Network for Radar surveillance of Animal Movements
    Swiss Birdradar Solution AG
    University of Exeter (GB)

    Financial support

    CTI – Commission for Technology and Innovation
    SNF – Swiss National science Foundation
    COST – European cooperation in science and technology


    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?
    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.
    Bruderer, B., T. Steuri, J. Aschwanden & F. Liechti (2012):
    Vom militärischen Zielfolgeradar zum Vogelradar.
    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.
    Bruderer, B., D. Peter, A. Boldt & F. Liechti (2010):
    Wing-beat characteristics of birds recorded with tracking radar and cine camera.