Roughly 150 bird enthusiasts from more than two-dozen states are visiting northeast Minnesota this weekend hoping to see elusive owls along the North Shore of Lake Superior, Minnesota Public Radio reports.

Dave Hendrickson, a founder of the Sax-Zim Bog Winter Birding Festival, told MPR droves of the 10-inch-tall boreal owls fly to Minnesota from Canada about every four years when the rodents they eat drop in numbers.

"There's a lot of activity of owls along the North Shore right now, and a lot of birders are probably causing traffic jams on Scenic 61," said Hendrickson. "You know where the owls are by looking at the crowds of people."

The Duluth News Tribune notes the festival quickly filled to its maximum capacity after a story in the New York Times. Hendrickson told the newspaper he had to turn away at least 20 people.

You can learn more about boreal owls at The Owl Pages or at the Minnesota DNR’s web page.