Large-scale bird migration monitoring using operational weather radar

Monitoring of large-scale bird migration is a challenge because of the absence of measurements at the population level. Weather radars can provide such measurements. To monitor bird migration across Europe we use the bird density retrieval algorithm developed by Dokter et al. (2011) on data from the European radar network OPERA. Unlike the NEXRAD network, the European network is very heterogeneous, both in radar types and in operational practices. This means that the application of the algorithm to data from this network is not straightforward, not least because of the different data formats employed. In particular the amount of clutter close to the radar (within 25 km) is an important factor determining the quality of the bird retrievals. The algorithm uses a predefined clutter map to select and remove clutter-affected pixels before quantifying bird densities. An automated clutter map generator based on historical radar data has been developed and shown to be effective.

We show results of the application of this bird retrieval algorithm to 61 radars in 12 European countries. All radar stations delivered volume data for a test period in 2011 from 15 August to 15 September. This allows for the monitoring of bird migration across Europe at an unprecedented scale.

Dokter, A.M., F. Liechti, H. Stark, L. Delobbe, P. Tabary, and I. Holleman (2011), Bird migration flight altitudes studied by a network of operational weather radars, Journal of the Royal Society Interface, 8, 54, 30-43, doi:10.1098/rsif.2010.0116.