A broad-winged hawk carrying a frog. Broad-wings eat small mammals, birds, amphibians, reptiles, and insects. (Jim Williams/The Minnesota Star Tribune)

A broad-winged hawk, defending nest and chicks from even suggested observation, will protest with a shrill scream, a definite caution.

Then come very close flybys, not-so subtle warnings to get the heck out of there.

Eventually, if you just don't get it, the hawk might fly into the back of your head. Unseen, no warning, the back of your head.

It knocks off your hat, an unambiguous message. If you're bareheaded, it might drag its talons across your scalp. Take that!

Incoming! (Jim Williams/The Minnesota Star Tribune)

Earlier this summer a broad-wing was nesting in the Shoreview yard of Carol and Duane Young.

Carol told me the bird hit her hard enough to raise a lump. Duane had a minor scrape and bled a bit during this weeks-long scenario. During one encounter he had to retrieve his cap three times.

Fly-by warnings were routine. Carol sometimes carried a rake held high to protect her, like a standard bearer in a parade. At times she wore a bike helmet.

"This is the fourth week the bird has been after us," she said in mid-July.

Broad-winged juvenile hawk in the nest. (Jim Williams/The Minnesota Star Tribune)

I drove to the Youngs' to see for myself. The bird warned me. I ignored her. The bump I received felt like a gentle "header," the soccer term for advancing the ball with your head.

After my visit to the battleground, I reached out to Mark Martell, an ecologist with raptor experience.

'I've been attacked by horned owls, barred owls, and goshawks when I was banding chicks," he told me. "But I deserved it for handling their chicks without their permission."

The owl hit him in the face with her talons. He needed stitches.

"The broad-wings will stop being aggressive as the chicks start dispersing," Martell said.

He was right. I saw the hawks on July 11. Eleven days later Carol e-mailed, telling me she hadn't seen the birds for three days.

"First the babies were gone, and then the mother left. We're happy to be able to move around our yard again," she told me.

The mother hawk during a calm moment. (Jim Williams/The Minnesota Star Tribune)

Broad-wings are birds of the forest (or wooded neighborhoods). Hunting from perches, they often can be seen on power lines, watching the weedy roadside for prey.

Broad-wings eat small mammals, birds, amphibians, reptiles and insects. I've watched a broad-wing capture frogs in the swampy wetland behind our home.

This species gets special attention in Minnesota in mid-fall for its sometimes spectacular migration following the Lake Superior shoreline into Duluth.

The Hawk Ridge Bird Observatory in that city recorded 101,698 migrating broad-wings on Sept. 25, 2003, a record.

Annual average count for all 20 of the migrating species of hawks and owls is 76,000. Broad-wings can dominate on a good day in late September or October.

The birds drift into view, circling in wide groups known as kettles. There can be hundreds of hawks — hundreds of broad-wings — in a single kettle.

They pour out of northern woods, riding wind to the lakeshore, to Duluth and beyond. They avoid the lake.

Excellent viewing can be had from a rocky ridge above the city. The birds are searching for updrafts, small-scale currents of rising air. The birds float and glide, rarely flapping their wings. Observation is best in September and October.

The birds are bound for warmer winter climes.

See hawkridge.com for migration numbers. Hawk Ridge will celebrate 50 years of observation Sept. 22-25.

Lifelong birder Jim Williams can be reached at woodduck38@gmail.com.