Smith: Canada geese grouping up before molt migration

One minute the early evening sky above the Menomonee River Parkway in Wauwatosa was clear except for the darting silhouettes of a half dozen chimney swifts and barn swallows.

The next minute a "horse of a different color" dominated the airspace.

"He-onk, he-onk, he-onk!" 

A flock of at least 20 Canada geese winged in just above the treetops from the southeast.

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The loose V-formation shifted and split as if the birds were having a disagreement about where to roost for the night.

The lively debate continued even after the birds disappeared from my line of sight.

Canada goose sightings in Wisconsin are about as common as drive-through restaurants.

But my interest was piqued Tuesday evening when I saw the talkative flock.

It was a sign that a seasonal honker phenomenon was at hand – the molt migration.

Among native Wisconsin wildlife, Canada geese are among the best-adapted to the mix of agricultural, suburban, urban and natural habitat in the state.

They, along with white-tailed deer, have been able to increase to nuisance levels in many parts of Wisconsin in the 21st century.

But unlike deer, geese undergo an annual transformation that makes them unusually vulnerable.

Each summer the birds shed, or molt, their wing and tail feathers. As new ones grow in, the honkers are unable to fly.

The flightless period lasts about four weeks, according to the U.S. Fish and Wildlife Service.

The molt is timed to occur on the breeding grounds when adult birds are tending broods. 

But Canadas don't breed until they are 2 to 3 years old, and other adult birds fail at nesting. And some other nesters have their young adopted by more experienced pairs.

All of these geese without goslings get out of town in summer.

In one of the marvels of wildlife behavior, these birds form groups and fly north to areas where they can safely live flightless for about a month.

"It's certainly one of the reasons Canada geese are thriving," said Bill Volkert of Dundee, retired naturalist at the Horicon State Wildlife Refuge. 

Volkert said honkers find spots with good food supplies and access to water, their primary means of escape from predators.

In addition to safety for the molters, the mass movement eases pressure on the breeding grounds in Wisconsin. 

"It's ingenious," Volkert said. "As far as wildlife systems go, it's a prime example of one that continues to work very well in the 21st century."

The molt migration of geese in North America was likely first documented in 1959 along the western coast of Hudson Bay in Canada.

The behavior also is observed in other waterfowl and in other parts of the world.

One of the best known molt migrations in Europe involves the common shelduck. About 200,000 of the birds gather each summer to molt in the Walden Sea off Germany.

The common goldeneye also does it. 

But in North America, it's best known in the big black-and-white bird that honks.

Regional reports of larger flocks of geese began coming in this year during the last week of May. On the Wisconsin Birding Network, Bob Russell of St. Paul noted the behavior on May 26. Kevin Seidel did the same in La Crosse County the next day.

Volkert said the nonbreeders and failed breeders first assemble into local groups. The flocks will stay together during short, low flights as they move between roosting, loafing and feeding areas.

These birds are noticeable by their groupings and their vocalizations.

"Adult geese with goslings are typically very quiet," Volkert said. "They don't want to call attention to themselves. But you can usually hear the molt migrators before you can see them."

The main movements north begin about the second and third week of June, said Taylor Finger, migratory game bird ecologist for the Department of Natural Resources,

"That's about the time the ice is off James Bay," Finger said.

These molt migration flights are also distinguishable due to their altitude. Instead of short hops done at a couple hundred feet, the migrators are often 1,000 feet or more in the air.

Where do they go?

About 70% of Canada geese from Wisconsin fly to Ontario to molt, with most in the James Bay region, Finger said.

Two years ago Finger traveled north to James Bay with other members of the Mississippi Flyway committee to participate in a banding project.

The group spent 10 days in a camp and banded 3,500 geese, including locally breeding Canadas (part of the Mississippi Valley Population, or MVP), snow geese and molting Giant Canada geese (the birds that breed in Wisconsin).

The flightless birds were easily rounded up and herded into net pens for banding and release.

The work helps add data points to the movement patterns of the various birds, as well as track the relative population changes.

"They've been seeing more Giants in James Bay in summer," Finger said. "That's raised a concern that they will outcompete the MVP geese in an area with relatively few resources."

Finger said the crews often had mixed flocks in their banding pens – the Giants were nearly double the size of the MVP birds.

The birds that fly from Wisconsin to Canada to molt typically stay north of the border until mid to late August, then fly south, Finger said, returning slightly ahead of the fall migration of the MVP geese.

Not all molt migrators fly to Canada, though. Banding studies have shown a small portion of the birds travel to spots in Wisconsin such as Crex Meadows State Wildlife Area near Grantsburg.

In either case, the flight is "a piece of cake" for a Canada goose, Volkert said.

"Geese will commonly make a nonstop flight from Hudson Bay to Horicon Marsh (about 900 miles) if the winds are right in fall," Volkert said.

Keep your eyes peeled in the coming days and weeks. 

If you see a high "V" in the sky flapping north, you'll know it's part of summer vacation, goose style.