I’ve been reading some pretty heavy stuff lately; books about the rise of tyranny around the world and some godawful decisions coming out of the US Supreme Court. I needed to take a break, read something a little more uplifting.

And what could be more uplifting than a book about migratory birds?

A World on the Wing: The Global Odyssey of Migratory Birds takes sweeping look at these adventurous birds, from their globe-spanning migration routes to the neurochemistry that helps them navigate. Through it all you get a lovely sense of how these birds connect the world together.

The author is Scott Weidensaul, an ornithologist, researcher and writer specializing in migratory birds. He’s written over 30 books on natural history.  Weidensaul takes a scientist’s viewpoint, but the book is anything but dry facts and figures. I found some parts very moving and many parts just plain astonishing.

A World on the Wing: The Global Odyssey of Migratory Birds
By Scott Weidensaul
W. W. Norton & Co., New York, 2021

Feats of Flight

In almost every chapter of A World on the Wing, Weidensaul tells us something amazing about bird migration. Here are just a few examples:

• Godwits, a shore bird, migrating from an island off the coast of Chile to their nesting grounds in southern Alaska, fly up the Pacific coast of South America, across the Gulf of Mexico and up through the Great Plains for a brief rest – a seven-day nonstop flight of 6.000 miles.

• Their cousins, the Hudsonian godwit make even longer flight: Alaska to New Zealand across the open Pacific: 7,000 miles, 9 days, nonstop.

• Their total roundtrip migration is over 18,000 miles. Other birds log similar distances each year.

• Some birds spend seemingly impossible amounts of time in the air, like the common swift which does not touch land for up to 10 months of the year.

• Most of these migrating birds weigh just a few ounces.

• They undergo incredible physiological changes before, during and after migration. They put on so much weight (relatively speaking) preparing for migration that “by human standards, premigratory birds are obese, diabetic, and likely to drop dead of a heart attack at any moment.”

And the way the actually navigate around the globe is something out of science fiction.

Threats

Human activity threatens migratory bird populations and habitats, just like it threatens every other part of the natural world. Weidensaul looks directly at many of these threats throughout the book, typically picking a single bird species as a case study.

Although he doesn’t group them this way, I’d put these threats into three categories:

I’ll call the first group “point threats.”  These are threats that affect either a single species or occur in a single location.  Some examples include:

• Swainson’s hawk nearly driven to extinction by pesticide use at its wintering grounds in Argentina.

• Golden-winged warblers whose nesting grounds in the forests of northern Pennsylvania have been decimated by logging

• Many of the small islands in remote parts of the world’s oceans that are the nesting grounds for hundreds of different species of birds have been infested by mice, rats, or other predatory mammals with devastating impacts on bird populations.

The good news is that these point threats can be addressed, albeit with heroic effort.

Weidensaul tells us how wildlife lobbyists and conservation organizations got the Argentinian government to ban the specific pesticide killing Swaninson’s hawks. Foresters are beginning to understand that in order to support migratory bird populations, it’s not enough to just replant trees. We also have to recreate forest complexity – the rich variety of tree species, height and age – that’s found in old growth forests. And on islands, like South Georgia in the far South Atlantic, where mice have been exterminated (using 100 tons of bait pellets), bird populations have rebounded quickly.

The second category consists of regional threats that affect many bird species over a large area. For example, in the opening chapter, Weidensaul describes how the extensive mud flats along the coast of the Yellow Sea in China have been dramatically reduced by reclamation projects. Birds like the critically endangered spoon-billed sandpiper that use this area as a crucial stopover point to rest and feed along their migration have suffered calamitous population declines. 

Development along the Gulf Coast of the southern US has had similar impacts.

What seems like ugly, smelly useless land for humans is often, in fact, host to a rich wildlife ecosystem.

Fortunately, the Chinese government has, for some unknown reason, agreed in recent years to scale back reclamation projects on the Yellow Sea mud flats.

The last category contains just one threat, the greatest of them all: global climate change. Weidensaul devotes an entire chapter to this, but it permeates the whole book.

The sad and terrible truth is that all the conservation efforts in the world won’t make a damn bit of difference if rising sea levels inundate bird habitats, or raging forest fires burn them to ashes.

“Migrants – especially long-distance migrants, those that already exist in a fragile balance between distance, time, physiological ability, seasonal resources and predictable weather – are among the species on which the hammer will fall first and hardest.” [p. 191]

Connecting Flight

The thing I found most striking about A World on the Wing was the vivid way it showed how migrating birds connect the whole world together.

We encounter birds mainly in our backyards or neighborhood parks. Maybe we notice they mostly disappear in winter and reappear in spring. But they seem to us like features of the local landscape.

But birds see the world differently. They see the world as a connected whole, a circle linking their breeding grounds, their feeding grounds and maybe a few stopover points in between; a looping path which may be 10,000 miles long or more.

Humans live in a single locality. Birds live over the entire geographic range of their migration. We haven’t lived like that since we were nomads, and even then, our ranges were nowhere near as far-flung as birds’.  

Writing about a little thrush at the end of the book, Weidensaul feels:

“Reverence for this extraordinary bird and billions more like it which by obeying their ancient rhythms knit up the scattered and beleaguered wild places of this world into a seamless whole through the simple act of flight.” [p. 374]

Unsolicited Feedback

I’ve never really been a birdwatcher. I’m quite nearsighted and most birds look like brown spots to me. But ever since I was a kid growing up in Canada, I’ve always loved watching the geese migrating in their flying-V formations. Last year I read Wintering: A Season with Geese about geese migrations in southwestern Scotland.

A World on the Wing is a great follow-on.

In some ways, the book feels a little disorganized. Each chapter has a theme, but there’s no obvious flow from one chapter to the next – you could read them in any order. Even within chapters, Weidensul jumps around quite a bit.

The book contains a lot of travel journaling recounting incidents like bear encounters during field work, and brief sketches of the researchers he travelled with or met. I know these details add a human touch to the book, but they didn’t interest me as much. I forgot most of the names almost immediately though, to be fair, these researchers deserve better for all their important pioneering work.

I did appreciate all the maps of migration routes and the 16 pages of color photographs.

Weidensaul’s writing is clear and in places quite moving, as when he describes witnessing flocks of tens or even hundreds of thousands of birds, like this 2018 mass migration of warblers seen by a researcher at Tadoussac, Quebec on the north Shore of the St Lawrence River:

“[at about 6:30 am] there was this point where we were looking out from this dune over the peninsula, across the St Lawrence, and there was just this wall of dots. Just, the sky was covered with birds, basically. And it was like that for the next nine hours.” [p. 152]

They estimated about 721,000 warblers had passed their observation point that day.

Researchers like Weidensaul might experience something like this once or twice in a lifetime. Most of us never will. Not anymore.

It’s a poignant reminder of something David Attenborough wrote about in A Life on Our Planet: the populations of most species of birds and animals have collapsed. The world is becoming an emptier place because of us. We’re awestruck when we see a few hundred geese in the sky, and so we should be. But even just a couple of generations ago flocks would “darken the skies” and experiences like the one at Tadoussac would have been common.

I think it’s time to put up a bird feeder in my backyard. It’s the least I can do.

Thanks for reading.

Related Links

eBird
World’s largest database of bird sightings collected from birdwatchers worldwide, hosted by Cornell Lab of Ornithology.

Merlin bird identification app for your phone developed by the Cornell Lab of Ornithology. Very cool! Identifies birds by sound as you walk around the park or lean out your window.

Motus Wildlife Tracking System (Motus)
An international collaborative research network run by Birds Canada that uses automated radio telemetry for research and education on the ecology and conservation of migratory animals. Site includes publicly available datasets.

Project SNOWStorm
Crowdfuned research on the annual movements of Snowy Owls.