US SCIENCE CONFERENCE: A weather radar system able to count the number of raindrops in a storm cloud is being used to track bats, birds and even insects flying through the night skies. Some of the systems are sensitive enough to pick up a bumblebee in flight 60km away.
The use of radar to track animals in flight has sparked the creation of a new science, "aeroecology", and a session at the American Association for the Advancement of Science meeting in Washington DC heard all about it. Aeroecology was little more than two years old, said Prof Thomas Kunz of Boston University.
Startlingly little is known about the species that occupy the skies above us after night falls. Techniques such as thermal imaging have been used to study this ecological niche but nothing can deliver the resolution provided by modern radar, he said. "How many organisms are there? It is one of the fundamental questions we always ask," Prof Kunz said.
There are 156 weather radar systems in the US that provide cover from coast to coast. Although designed for weather, they can also pick up the movement of night flyers, said Prof Phillip Chilson of the University of Oklahoma. Because these systems are already in place very little extra money was needed to pursue aeroecology and conduct an analysis of up to 20 years of stored radar data.
Ecologist Dr Winifred Frick of University of California described the use of radar as an "unprecedented tool" that would greatly assist her work. Discoveries are already being made despite the fact that this is a new science. She described how weather conditions often caused the "evening bloom" of insects to become compressed in a reduced area. The radar showed how the bats emerging from their dens in the evening fly in a "bat cloud" to feed on this convenient dinner.
The bats can eat as much as their own body weight in insects in a single night, thus providing an important service to humans. Being able to track them as they move from one food source to another will also help researchers understand bat predation of agricultural insect pests.
The planned installation of an even more sensitive radar system that polarises the radar signal will boost sensitivity still further, Prof Chilson said. The radar response should allow researchers not only to identify individual species of bird but also different types of insects while in flight.