Continued: Fall migration: A choir overhead

It was so early that it was still dark. When I went out to get the newspaper, I heard an eerie sound: the single-note calls of migrating birds as they passed overhead.

A river of birds moves across the sky on most autumn nights, usually without making a sound. However, when they become confused or disoriented, they call out.

The purpose of these calls, which are very unlike their daytime songs, isn't fully known. The birds may call to keep in contact with other birds. Or the calls may serve as a sort of traffic-control device.

As soon as dawn broke, the birds' unusual calls stopped. And as the sun rose, the migrants changed their tune to their more familiar daytime calls. I could hear vireos, warblers, a rose-breasted grosbeak and a chortling northern flicker noisily getting down to the serious business of rustling up breakfast.

After flying all night (which allows them to capitalize on the lack of wind and lower temperatures), birds need to feed to replenish their energy stores.

But that doesn't mean these migrating birds will show up at your feeders. Many of them are insectivores on the hunt for the high-protein punch provided by juicy insects. Others are fruit-eaters, looking for the grapes, berries and crabapples now in abundance.

They are likely to follow local chickadees around, however. As chickadees flit from bush to bush in search of a meal, they come to the attention of migrants, who are unfamiliar with the area. The traveling birds often follow behind the locals, confident that if the 'dees find a meal, there'll be enough for the visitors, too.

Following the river road

There's another river that looms in importance during migration season.

"Some 300-plus bird species spend all or part of their year on and along the Mississippi River," said Dan McGuiness, president of the St. Paul Audubon Society. "At times they settle down to nest or rest, at other times they use it as an international flyway during their seasonal migrations."

That's what the birds I heard on that early autumn morning were doing. Most likely, they had left their nesting areas in Canada or northern Minnesota a week or two earlier and were following the Mississippi, a route that will take them down the middle of the United States.

Some of these birds have only a few hundred miles to go. Others face journeys of thousands of miles. But they all take part in the natural, cyclical and miraculous journey we call migration.

Val Cunningham, a St. Paul nature writer, can be reached at valwrites@comcast.net.

Recent Lifestyle stories

Disappearing act - October 14, 2008

Disappearing act - Though it may seem as if the goldfinches are long gone, there are more of them around now than there were this summer. You just may not notice them. More