High tech bird count: Radar used to track raptors

  • Posted: Sunday, November 18, 2012 11:53 p.m.

AWENDAW — Bird counters usually head into a field or forest carrying binoculars and a pad to record what they see. But a South Carolina center went high-tech this fall, using radar in its annual count of falcons, eagles, hawks and other raptors flying along the coast.

Officials at the Center for Birds of Prey say it’s thought to one of the only places where modified marine radar is being used to help count raptors. And they say it should help increase the number of birds sighted by watchers on the ground.

The survey has been taken from mid-September through mid-November for the last 15 years as volunteers head into fields at the 150-acre center northeast of Charleston.

“We know that by counting migrating raptors and watching patterns over time we pick up trends,” said Stephen Schabel, the center’s director of education. “One of our missions is to monitor what is happening out there in the environment and its potential effects.”

A small, rotating radar dish linked to a computer was set up this year in a field adjoining the marsh. It was brought in by Sid Gauthreaux, a retired Clemson University professor, a member of the center’s board and an expert on bird migration.

The radar, set to a range of 3.5 miles, shows from which direction and altitude the raptors are approaching, long before they can be seen with the naked eye.

“We use the radar to cue us,” said Gauthreaux, who began using radar to track smaller birds about 15 years ago. “When you have a group of observers, the radar can actually up the count of raptors probably by as much as three times.”

However, preliminary counts show the birds’ numbers seem to be down this year, despite the new radar.

Gauthreaux said that may be due to changes in weather patterns. Large birds like raptors rely on thermals – columns of rising air caused by uneven heating of the earth – to get lift. If the weather patterns change, those thermals may be farther inland. That would make it less likely for the birds to be flying along the coast.

The counting at the center is carried out only in the fall. During the spring migration of raptors from South America to as far north as Greenland, the birds tend to fly farther west. The figures collected at the center go into larger surveys taken yearly by the Hawk Migration Association of North America.

The center plans a permanent deck and radar installation at the site with a monitor so watchers can easily see from where the birds are approaching. In the current setup, the computer is in a small trailer and the operator has to call out to tell watchers outside where to look.

Jim Elliott, the founder and executive director of the center, said that while some people think counting birds may not be exciting, it gets in your blood.

“When you look at a peregrine falcon fly over your head and you realize that bird may have flown 7,000 miles to get where it is, it’s moving. It really is.”

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Follow Bruce Smith at http://twitter.com/brucesmithap

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