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Black-and-white warblers are one of the neotropical migrants known to cross the Gulf of Mexico at night in large numbers. Keith Corliss

Radar used by more than just weather watchers

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Just a couple weeks ago an interesting little story caught my eye on the front page of the Forum. Dave Olson's piece described a certain peregrine falcon which had spent the night in south Fargo, presumably on its way to its nesting area on Baffin Island. But what made it intriguing was the fact that this bird - nicknamed Sparrow King - was fitted with a small GPS transceiver. Therefore its whereabouts, from winter grounds in Chile to its nest site in the Arctic, is easily ascertained.

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The tools available to the biological sciences keep growing every day it seems. Many are already in use for other reasons just waiting for someone to have that V-8 moment and apply them in an alternate way.

Such was the case about 50 years ago when a youngster named Sidney Gauthreaux was growing up in Louisiana. He was interested in birds, specifically migration. Living on the north shore of the Gulf of Mexico he had seen astounding numbers of birds appear overnight almost magically. Wooded areas around New Orleans would be fairly benign one day, then dripping with small songbirds the next. It was obvious a massive migratory movement was occurring during the night.

In 1957, one of the new weather radars was placed in Louisiana in hopes of better forecasting and warnings of hurricanes. In addition to picking up precipitation, however, Gauthreaux wondered if it wasn't depicting something else, something organic. It turns out he was right.

 "A weather radar functions by picking up minute droplets of water in the atmosphere," Gauthreaux said. "So it made perfect sense that radar designed to pick up small droplets of water would likely pick up migrating birds."

In the years hence much has been learned as it pertains to bird migration, especially trans-gulf movements. Some of the screen captures from the area are amazingly dense. A one-mile slice of radar beam has been known to depict 50,000 songbirds at one time, all moving across the water at night.

In addition to birds, however, other flying critters can reflect radar energy back to operators. When I first started flying in the Air Force, we were warned of the tremendous number of bats leaving roosting sites around some of our bases and to avoid taking off or landing at certain times. We young aviators were shown radar images of tremendous clouds of bats at several Texas bases as an example.

Sensitivity of newer radars is such that even insects are picked up. I would guess there has to be very large numbers in order to make that happen, but happen it does.

WDAY meteorologist Daryl Ritchison said, "I know the Mayville Doppler (radar) picks up insects, especially mosquitoes." He said he sees these radar returns when he is looking at wind patterns because mosquitoes are pretty much at the whim of moving air.

I'm not smart enough to interpret local radar returns and see birds but it's likely possible. The middle of May would have been a good time to look. I've been tallying the number of species seen in Cass County since the first of the year and have around 200 at the moment. In just a 10-day stretch - 10-19 May - I added 57 species to the list. Local birders consider this the pinnacle of the year, the top of the bell curve. Certainly there was a night or two during that time which must have shown some radar (RAdio Detection And Ranging) returns with songbirds.

Local air traffic controllers pick up birds too, particularly the larger ones, even though their radars are different. It's not uncommon to be flying in the local traffic pattern and hear a controller say, "You have traffic at one o'clock, altitude unknown, probably waterfowl."

Gauthreaux went on to pursue his interest and became a professor of biology at Clemson University. He now heads the Clemson University Radar Ornithology Laboratory, the only one of its kind that I know of. Work continues there on a variety of radar related issues. Their Web site states, "We also are using these data to develop continent-wide and regional migration maps and to build predictive models of migration for different regions of the United States."

While radar cannot track a specific bird, such as Sparrow King, it has become a useful tool to researchers for monitoring grouped movements. Who knows when the next piece of technology will transfer its use to biology. It could be already out there just waiting for the next curious teenager to come along.

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