'Aeroecology' uses radar to track flying animals

By Jason Palmer
Science and technology reporter, BBC News, Washington DC

Image caption,
The power of the method could be massively increased with the use of more, smaller radar units

The study of birds, bats and flying insects could be transformed by the use of technology designed for tracking storms, researchers say.

Meteorologists once treated the signals from flying animals as a nuisance that complicated their measurements.

But recent improvements in computing power and networking of radar stations have turned that nuisance signal into a valuable data source on animal ecology.

A panel told the AAAS conference that radar could spot a single bee at 50km.

Further improvements to the technique must be made before that level of resolution can be reached, however; now it is the storms that are complicating the signals that interest biologists.

But pioneer of the "aeroecology" field, Thomas Kunz, of Boston University, told the conference why radar is needed.

"One of the limitations we have in working with small animals like birds and bats and insects is that you can't put large satellite radio transmitters on them to understand their movements.

"So the whole concept of aeroecology is an integrated approach using many different tools to try to answer the questions about how organisms move and use the aerosphere."

Phillip Chilson is a meteorologist from the University of Oklahoma, who has been working with radar for two decades. He explained why radar is a potentially transformative tool for aeroecology.

"We already have well-developed networks of radar around the country and around the world - used for tracking weather and for tracking airplanes.

"There are as many as 510 government-owned and maintained radar (installations) in the US and 156 for weather radar; Europe has in the order of 200. We have a wonderful tool that we can use for exploring biology without much outlay of money from scientific sources."

Dr Chilson and Professor Kunz recently teamed up with biologist Winifred Frick of the University of California, Santa Cruz to look into the mystery of bat movements.

"Dr Kunz and I were meeting Dr Chilson about a year ago over breakfast and they kept talking about the 'QPE', and finally I asked what it is," Dr Frick told the meeting.

It stands for quantitative precipitation estimator - a numerical method to measure how much rain there is in a storm front.

Media caption,
Animal flight patterns could help scientists monitor how they are affected by man and the environment

"I paused and said, 'you can estimate the number of raindrops in a raincloud? Do you think we could estimate the number of bats in a bat cloud?'"

To calibrate their experiment, the team took a bat into a chamber where the degree to which it reflects radio waves could be measured.

"From those measurements and using radar, we've been able to adapt those QPE measurements to a 'QBE' - a quantitative bat estimator," Dr Frick said.

Although the field is only just getting started, the team's measurements are already paying dividends, Dr Frick later explained to BBC News.

"One of the things that's most exciting to me is that we sometimes see an airmass that's moving, like a weather front, and insects actually get trapped up in that - you can see the insects pooling up along this air mass.

Image caption,
Thermal imaging of bats is also aiding in the "aeroecology" effort

"If this happens to pass over the bat caves at sunset, the bats come out and distribute themselves right along that gust front and presumably gobble up those insects. Marine biologists probably think that kind of thing happens all the time in the ocean, but we've never been able to see that in the aerosphere."

Another aspect of the work is that decades of data from radar stations exists in archives, waiting to be mined for information about flying creatures.

Such a rich data set is crucial in conservation efforts, and understanding how birds, bats and insects are responding to long-term drifts in their environment.

"Lots of people have been able to look at seasonal variations - people do this with plants, to look when the start of spring is changing, how the flowering time changes," Dr Frick explained.

"We didn't have a tool to look at that same kind of process for vertebrates; now we're looking at the timing of purple martins - aerial insectivorous birds - when their migration starts and stops, and we can do that with bats. That'll be really important for understanding the long-term implications for climate change."

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