SALT LAKE CITY — TV viewers know the images: a meteorologist standing in front of the big screen, pointing out the green and blue blobs of rain or snow that’s heading our way.
Last Monday night, staffers on duty at the Salt Lake office of the National Weather Service saw that image on their computer screens, only this time no storms were predicted.
“So it was about 5:45 on Monday evening,” said Randy Graham, science operations officer with the National Weather Service. “You could see some echoes on the south end of the lake, on what was otherwise a clear day, so we knew it wasn't a weather feature.”
The radar screens showed a 5-mile-wide, 40-mile-long radar image that stretched from the south end of the Great Salt Lake all the way to Juab County.
The image was an event the weather service sees every December, as thousands of tundra swans migrate from Canada and Alaska for the warmer climates in California — a distance of more than 3,000 miles.
“They travel in massive groups,” says Janice Thompson, a zookeeper at Hogle Zoo. “They'll have large flocks, but the flocks will just keep coming one on top of the other, so if you look at it in a large scope, you can have a group of birds in the thousands.”
The birds are big, too. Adults weigh about 15 pounds and can have a wingspan of more than 5 feet.
The weather service radar tracked this line of birds for about an hour and a half. The Great Salt Lake is right in the middle of the swans' migratory path and serves as a rest area during their long journey.
“Twice a year, they do migrate,” Thompson said. “They migrate because they need to breed. In the summer months they're up in Canada and Alaska on the very rim of the Arctic, but it’s too cold for them in winter. They come down and they branch off into four segments. We have this perfect area for them to go through due to the fact of all the waterways we have and also farmland, where there’s plenty to eat.”
Tundra swans make their migratory flights at night and rest during the daytime hours. They’re the second largest swan in the world; trumpeter swans are bigger. Tundra swans extremely hearty, strong and don’t need any special types of foods to survive.
Next spring, these birds will return north to their breeding grounds. And radar could pick them up again.
“We might”, Graham said. “Apparently they return in March going the other direction. Perhaps we'll see (a large flock) in mid-March going the other way.”
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