One August day last year, birdwatcher Dolores Hagen observed a stunning sight in her back yard: scores of hummingbirds gorging themselves from nectar feeders.

“The sound was incredible,” she says of the hum produced by their wings. Based upon the amount of sugar water consumed, she estimates nearly 300 birds visited her yard that day.

That occurrence served as a catalyst for a first-ever event in Minnesota — the upcoming capture and banding of ruby-throated hummingbirds as they prepare to migrate south.

The Henderson Hummingbird Hurrah Aug. 28-30 will be a birders’ potpourri of displays, author presentations and the delicately meticulous task of banding the tiny birds.

“I’m told by the Audubon people that birders far and wide will be coming to Henderson because the banding of hummingbirds is extraordinary,” says Hagen, who operates a birding information center in Henderson.

A virtually invisible “mist net” resembling an oversized volleyball net is used to capture the birds for banding.

The event was created by the Henderson Chamber of Commerce and Audubon Minnesota to draw attention to a phenomenon.

Hagen says that in the past 15 years Henderson has experienced a steady increase in the summer breeding population of ruby-throated hummingbirds, as well as the number of them using this area as a pre-migration feeding station.

“When people think of birds, they think of the Mississippi Flyway, but hummingbirds think the Minnesota River is a great flyway. It looks like Henderson has become a staging ground” for southward migration.

Hummingbirds must consume nectar from flowers and artificial feeders to gain twice their body weight for the grueling flight across the United States, the Gulf of Mexico and into the tropics.

They travel nearly 2,400 miles twice a year — once to migrate north to breed, and again to return to their wintering grounds.

For a full list of Hummingbird Hurrah activities, go to www.hendersonmn.com.