Combining citizen science and weather radar data to study large‐scale bird movements

The study of large‐scale animal mass movements requires suitable large‐scale sampling methods. Weather radar (WR) has been known to register biological targets since the 1960s. Arranged in large networks, radar is suitable to study regional to continent‐wide dynamics of aerofauna and to respond to increasing human–wildlife conflicts in the air. Tools for the spatiotemporal validation of faunistic interpretations of WR measurements in situ are only sparsely available. Citizen science (CS) bird observation repositories established in the past 20 years have accumulated millions of entries of species‐specific information well beyond their time of existence across vast areas. Together with other CS data sources, these databases can relieve the taxonomic shortcomings of WR and thus extend and refine the use of WR data. CS and WR data combined can efficiently provide large amounts of species‐specific data in three dimensions in a short time at low or no cost. Species‐specific data are particularly relevant to tackle loss of biodiversity, one of the greatest challenges in today's world. In this forum paper, we present features and qualities of ornithological CS and WR data, and their potential to provide unprecedented insights into regional to continent‐wide aerial movements of birds. We aim to discuss specific fields of applications where maximum information yield is to be expected, which is otherwise inaccessible, and in which way combined approaches would support biological research and derived data products and services for stakeholders, e.g. in aviation and the general public as beneficiaries.