(Undated) -- The Midwest is currently at the center of songbird migration. Annette Prince with the Chicago Bird Alliance says the largest number of them are flying through Iowa.
"Millions of birds come through," Prince says. "Birds are currently coming through from their summer breeding areas in the northern United States and Canada."
She says it may not always be easy to tell because they aren't flying during the day.
"We don't see all these millions and millions of little birds because they're flying at night overhead and then they're resting and feeding during the day," Prince says.
It's not impossible to see them, though. Prince says it takes is a clear night and a telescope.
"Sometimes we say it's like a carpet of birds overhead," Prince says. "If you can put the scope on the moon, I've seen photographs of bird silhouettes crossing the moon."
The Cornell University Birdcast.info tracks the migration using the same radar used to track rain and storms. 162 million birds are migrating now with another 220 million expected Thursday into Friday.
Below: The Birdcast radar screenshot shows projected migration Thursday August 29 into Friday August 30.