(CNN) - Do you see those green blips on the radar moving north?
It's not wind, rain or UFOs. They're birds!
With cold weather coming to a close, many bird species are heading back north for the summer.
National Weather Service radar in Fort Worth, TX, caught some of that migration.
If you look up and see giant flocks blacking out the sun, don't harness your inner Alfred Hitchcock and seek shelter.
They're just doing what they've done for millions of years.
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