By Nala Rogers
Posted on August 30, 2016
A new visualization tool for
radar data is revealing bird migrations as they have never been seen before.
With the new tool, birds’ nocturnal journeys appear as blue streaks that sweep
across a map like raindrops on glass.
“[Songbirds] all travel at night,
or almost all of them. So most of the migration, in fact, you can’t even see,”
said Judy Shamoun-Baranes, an ecologist at the University of Amsterdam and
first author of the study published yesterday in PLOS ONE.
“You’ll only see them coming in in the morning, maybe, and landing, or you’ll
suddenly see birds that weren’t there the day before.”
Humans may have difficulty seeing
in the dark, but radar stations — the same ones that track weather or enemy
aircraft — pick up signals from birds regardless of whether the sun is shining.
Radar detects objects by sending out radio waves and measuring how long they
take to bounce back. Birds move differently than drifting objects like seeds,
and with the right software, researchers can isolate signals from large numbers
of birds moving together. These signals contain information about how fast
birds are moving, what direction they’re traveling and approximately how many
are in the air. But the information is so complex that it can be hard to
interpret, especially over large areas with multiple radar stations.
“For us, what’s always difficult
is that you’re trying to integrate all of that information at once,” said
Shamoun-Baranes. “You want to be able to tell a story, in a relatively simple
visualization, which really gives you this feel for the flow of movement across
a large landscape.”
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