Birds flood into Minnesota during spring migration

An American redstart, a warbler resembling a small Baltimore oriole, spent last winter in Belize, feasting on insects. And a Baltimore oriole flashed through trees along the Panama Canal all winter long, dropping into fruiting trees to feed.

And then, sometime in January, subtle external cues begin to cause internal changes within the birds' bodies: They began to eat more, putting on weight for the coming arduous flights ahead. Changes in hormones and the weight gain made both birds restless. One night in February, the oriole lifted into the sky to begin his long journey northward, and the redstart set off in March.

The oriole reached Minnesota on May 4, perching in a tall cottonwood along a lake to sing his exuberant spring song. The redstart arrived a few days later, claiming a nest territory on the edge of a small woods. (By the time they arrive, two other large groups of migratory birds — ducks and shorebirds — have already passed through.)

Like the oriole and redstart, billions — yes, billions — of other songbirds left countries like Brazil, Colombia, Panama, Belize, Mexico and the southern United States earlier this year. They're all rushing to reach northern places where they'll find a mate and raise their young. For some, those spots are in Minnesota.

Challenges lie ahead

Migration is hazardous to birds: They travel through weather changes and turbulent storms and they need to find food at every stop, in unfamiliar surroundings. They must avoid predatory hawks and cats and other dangers and they have to travel quickly in order to be first in line to claim a good nesting site. They generally travel at night and must call on many innate and learned skills to end up where they want to go. These twice-a-year journeys demonstrate birds' incredible ability to navigate, as well as their intelligence and endurance.

Why do they do it? Why not just stay put, like our woodpeckers, cardinals and finches do? Most long-distance migrants leave because their sources of food — insects and fruit — disappear as winter approaches, so they travel in order to be able to eat. And then migration, with all its dangers, turns out to be safer for many than staying put.

A study by researchers at the Cornell Laboratory of Ornithology found that migratory birds had a higher survival rate than birds that remained behind in the United States.

"Contrary to popular thought, birds wintering in the tropics survived the winter better than birds wintering in the U.S.," said Andrew Farnsworth, co-author of the Cornell study.

Spring migration by songbirds has been carefully calibrated over the eons to synchronize with conditions in the natural world, especially the availability of insects to fuel their flights (and feed their young). Most migrants aren't attracted to our bird feeders — instead, they're looking for just-hatched caterpillars chewing on newly emerged leaves. (As the climate warms, caterpillars hatch earlier, but birds aren't able to change their behavior as quickly, fraying this natural synchrony.)

Such exuberant songs

The quiet of winter gives way to the symphony of spring. Mornings are filled with birdsong created by both migrants and residents, a loud chorus of cheeps, chirps, whistles, musical notes, buzzes and raspy sounds.

"Birds are the great communicators of the animal world," says science writer Jennifer Ackerman. "They talk through everything — courtship and fighting, foraging, traveling, avoiding predators and raising their young."

Wherever you live, migrating songbirds will be moving through your area this spring, most flying at night and putting down to rest during the day. Stay alert through May and you may catch sight of birds engaged in migration, one of nature's miracles.

St. Paul resident Val Cunningham, who volunteers with the St. Paul Audubon Society and writes about nature for local, regional and national newspapers and magazines, can be reached at valwrites@comcast.net.

ETA for migrants

Mid- to late March: Ducks and geese begin flooding in.

Mid- to late April: Shorebirds and early songbirds appear.

Early to late May: Songbird migration peaks, hummingbirds zip in.

Mid-June: Migration is almost over, stragglers bring up the rear.

They're all around us

Writer and naturalist Kenn Kaufman says that "no matter where you are, you have a chance to see some migrating songbirds." After flights of 200 miles or more, songbirds drop down to rest and feed to get ready for the next night's journey.

Look for them in trees and shrubs anywhere: in city parks, the edges of woods and forests, even your own backyard. Migrants are most active in the early morning, as they forage hungrily for food. Not every day will be the same: Watch for mornings with clear skies, warm temperatures and steady winds from the south. And a morning after a showery night can produce a bonanza of newly arrived migrants.

World Migratory Bird Day

May 14 is World Migratory Bird Day, to spotlight the need to conserve migratory birds and their habitats. Check online for celebrations near you.

Two great books

Migration is a complex and astonishing phenomenon, and Scott Weidensaul, researcher and author, knows this better than most and writes beautifully about it. Two of his recent books, one for adults, one aimed at children, bring migration alive.

Kids can follow the journey of a small yellow warbler as she travels from Central America to Canada, in "A Songbird's Journey." Richly illustrated by Nancy Lane, Weidensaul's engaging text will have kids cheering for the intrepid little bird as she faces challenge after challenge, helped by three families along her route. Gryphon Press, which specializes in picture books for children celebrating the human/animal bond, will issue the book on May 10.

Adults will revel in "A World on the Wing," as Weidensaul brings to life the latest research on bird migration, focusing on species on the move around the globe. His book is full of revelations about the billions of birds flying, north to south or east to west, twice each year.