As the climate changes, migratory birds are losing their way

Living on Earth
Bird migration

Every spring and fall, a journey of thousands of miles begins, as migrating birds find their way between breeding and overwintering grounds.

It’s an amazing phenomenon that naturalist Kenn Kaufman brings to life in his new book, "A Season on the Wind: Inside the World of Spring Migration." Kaufman is also the author of the "Kaufman Field Guide" series and is a contributing field editor with the Audubon Society.

Related: Citizen scientists have been taking an annual ‘bird census’ for over a century

Bird migration is largely invisible to most people because it happens primarily at night, Kaufman says. But if you go outside at dawn near a spot where migrating birds congregate — like along the coast of Lake Erie in Northern Ohio, where he lives — you will see something extraordinary.

“It's just a fabulous experience,” Kaufman says. “You hear the night sounds, of course — there are the frogs and insects and there are a few night birds, like screech owls, that are calling. But then you hear the sounds of these birds. A lot of these nocturnal migrants are calling in flight, making these little chip notes, little buzzes and things. And you hear more and more of that as the birds come lower.

“Some of them are coming in from the south and landing in the trees, but then, as it starts to get light, you look out and there are small birds flying along, paralleling the edge of the lake,” he continues. “There are others that are actually coming in from the north because when these birds are migrating if they're out over the open water when it gets light, they'll actually climb somewhat higher and look around. … [I]t’s just an amazing amount of movement. It's like the whole world is alive with this movement of birds.”


In the summer, the eastern kingbird lives in the eastern two-thirds of the US and southern Canada, feeding on insects in open country. In winter, they gather in flocks in the Amazon rainforest, feeding on small fruits in the treetops.


Courtesy of Kenn Kaufman

For Kaufman, spring migration evokes “a sense of resurrection almost, a sense of rebirth. Especially if you're in northern Ohio and things have been frozen solid all winter and then start to thaw out and all these birds come back. It's just such a wonderful feeling that I can't help just wanting to go out and celebrate.”

While migrating birds will tend to congregate in specific locations each year, Kaufman says the notion that birds stick to predetermined flyways is a dated concept.

The idea of bird flyways was first developed by people studying duck migration, he explains. Studying duck migration was easy because scientists could catch a bunch of them at a water area, put bands on their legs and then later ask the hunting community to send in the duck bands from wherever they shot the ducks. This quickly gave them a sense of where these birds had gone.

“If you could look down on North America from outer space on a night at the peak of migration, you wouldn't see rivers of birds flowing toward the north. It would look more like a blanket of birds being pulled northward." 

Kenn Kaufman, contributoring editor, Audobon Society

Ducks do sort of follow specific flyways from one water area to another, but the great majority of birds don’t. “If you could look down on North America from outer space on a night at the peak of migration, you wouldn't see rivers of birds flowing toward the north. It would look more like a blanket of birds being pulled northward,” Kaufman explains.

Related: Beyond borders: Why we need global action to protect migratory birds

For serious birders, fall migration is even more exciting, Kaufman says. For one, there are simply more birds to see. “The total population is higher because the birds have been hatching young all summer. All these young birds are migrating south for the first time. So, the numbers are higher and the young birds are more likely to wander out of range. You'll get more rare birds and more birds in places where they shouldn't be during the fall.”

To a large extent, bird migration remains a puzzle. Some birds, like cranes, swans and geese, learn their migratory routes and pass the information on to their young. But most small migratory birds travel by instinct.

Yellow Warbler

Warblers are the most popular of the migratory songbirds that mark the peak of spring migration. The Blackburnian warbler spends the winter in the Andes in South America, migrates north in spring through Central America, across the Gulf of Mexico, through the eastern US, heading for breeding grounds that are mostly in the spruce forests of Canada.


Courtesy of Kenn Kaufman

“You can just drop a warbler off in the north woods and it will find its way from northern Alberta, say, down to Brazil, without any guidance, without anyone showing it where to go,” Kaufman says. “It's amazing that they've got this instinct.”

A lot of the small birds that migrate at night can navigate by the stars or detect the Earth's magnetic field, Kaufman notes. Others can hear low-pitched sounds, like the sound of waves crashing on the beach from many miles away and use the sound as a navigation aid. “We're still figuring out and still learning some of the things they use, but the navigational abilities of these birds are extraordinary,” Kaufman says.

Climate change and the global collapse of insect populations may have a negative impact on migratory birds in the coming years. Evidence is mounting that in some places birds are on the move five to ten days earlier than in years past, yet still may be missing the peak of insect season when they arrive at their destination. Since the large majority of birds feed primarily on insects, scientists fear the consequences of birds being out of sync with the insect population.

Related: Spring's uncertain arrival poses problems for migrating birds

People who live at or near a stop for birds on their migratory path can do a few simple things to make the local environment more welcoming and helpful to these traveling birds. Keep cats inside. Grow native plants. Eliminate or at least reduce the use of chemical pesticides. Support conservation efforts and protection of native habitats.

“Just by voting on certain issues, people can affect what happens with wildlife habitat in their local area,” Kaufman says. “It's worthwhile for people to educate themselves about the issues and pay attention to what policy changes are going to have an impact on bird life.”

This article is based on an interview that aired on PRI’s Living on Earth with Steve Curwood.

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