Many insects of economic importance are highly mobile, with populations showing rapid changes in spatial distribution due to windborne migration. Data on such migration behaviour can contribute to pest management strategies, but are hard to acquire due to the intrinsic difficulty of observing insects at high altitudes. In collaboration with scientists at the Natural Resources Institute (NRI) Radar Unit, we are using a new type of autonomously operating vertical-looking radar (VLR), to investigate the abundance and behaviour of insects flying at altitudes between 150 m and 1200 m at two localities: Rothamsted Research and the NRI laboratory at Malvern, Worcestershire. With this system, readings are taken within 15 height bands, 45 m deep, separated from each other by a non-sampling interval of 26 m. The VLR is programmed to collect signals from all the height bands for a five minute period every 15 minutes, 24 hours a day. After each sampling period, seven parameters describing the speed, direction, alignment, shape and size of targets are extracted from each collected signal, analysed and downloaded to a PC-mounted database.
The minimum size of insect that can be detected by VLR depends on its altitude in the radar beam. The minimum size resolution at the lowest height band (150 m) is c. 2 mg, and at the highest height band is c. 15 mg. Thus, insects with a body mass of >15 mg can be detected at all altitudes covered by the beam. Further improvements in resolution are technically feasible but would be prohibitively costly, for the time being at least. Our ability to establish the taxonomic identity of radar targets is still limited, but interpretation of data is assisted by comparison with trap catches from nets suspended from helium-filled balloons, and from the RIS light- and suction trap samples.
Flight Orientation Behaviors Promote Optimal Migration Trajectories in High-Flying Insects. Science. 5 February 2010: Vol. 327. no. 5966, pp. 682 - 685 DOI: 10.1126/science.1182990. Abstract, Reprint, Full Text.
Recent Applications of Radar to Entomology', an article from Outlooks on Pest Management – February 2007. © 2007 Research Information Ltd. All rights reserved.
Radar studies of butterfly migration at altitude (Rebecca Nesbit)
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