Take Note: Pennsylvania Native, Nature Writer On 'The Global Odyssey Of Migratory Birds'

Jul 16, 2021

Credit Chris DeSorbo

Scott Weidensaul is a naturalist and writer, the author of about 30 books, including one out in March of this year, “A World on the Wing: The Global Odyssey of Migratory Birds.” In the book, Weidensaul takes readers across the word to see the incredible feats of migrating birds. We learn that some birds travel thousands of miles at a time and many of them make those treks in the darkness of night. Weidensaul also writes about the added challenges birds are facing from loss of habitat and climate change. A native of Pennsylvania, Weidensaul got his start writing about birds and nature in a column for his local newspaper, the Pottsville Republican in Schuylkill County. Along with writing and observing, Weidensaul is an active bird-bander, helping track hummingbirds along with founding SNOWstorm, which uses technology to track snowy owls.  Weidensaul spoke with WPSU's Anne Danahy about his new book.

Here's the interview:

Anne Danahy 

Welcome to Take Note on WPSU. From my home studio, I'm Anne Danahy. Scott Weidensaul is a naturalist and writer, the author of about 30 books including one out in March of this year, "A World On the Wing: The Global Odyssey of Migratory Birds." In the book, Weidensaul takes readers across continents to see the incredible feats of migrating birds. We learn that some birds traveled thousands of miles at a time, and many make their journey in the darkness of night. Weidensaul also writes about the added challenges birds are facing from loss of habitat and climate change.

A native of Pennsylvania, Weidensaul got his start writing about birds and nature in a column for his local newspaper, The Pottsville Republican in Schuylkill County. Along with writing and observing Weidensaul is an active bird bander helping track hummingbirds along with founding SNOWstorm, which uses technology to track snowy owls. Scott Weidensaul, thank you for joining us.

Scott Weidensaul 

Thanks, Anne. It's a pleasure to be here.

Anne Danahy 

In "The World on the Wing," you paint a picture of birds that spend days on end flying, either for migration or because that's just how they live. The frigate bird, for example, can travel for two months at a time. And that's kind of mind blowing, until you get to the common swift, which spends 10 months in the air at a time. What's known about how they actually do that?

Scott Weidensaul 

Well, and then on top of that sooty terns, which are a tropical nesting species, once the young sooty terns leave their nesting ground, they don't return to land for about four or five years. And they virtually never land during that time. Birds are just astoundingly aerial. Many of these species, you think about if you're going to spend days or weeks or months or years on a wing, you got to figure out some way to sleep. And birds do that by using something called unit hemispheric sleep where they basically put half their brain to sleep for a couple of seconds at a time and then just alternate halves of their brain back and forth, and back and forth, and back and forth, almost endlessly. Not only do they do that, they avoid the effects of sleep deprivation, the reaction time and their reflexes actually get better. Under those circumstances.

Anne Danahy 

While they're doing this, then they can just kind of coast along on the currents?

Scott Weidensaul 

Well, one half of their brain and one of their eyes are awake and paying attention and the other half of their brain is asleep. And actually some mammals do this. Marine mammals like dolphins and whales, and manatees, which actually actually consciously breathe, you know, if they fell completely asleep, they'd drown. And if you've ever had a bad night's sleep the first night, you've slept somewhere, that's called first night effect. And in a way, it's similar in humans to what birds are doing, where part of your brain doesn't go completely to sleep. It's probably, you know, an evolutionary holdover from the days when you didn't want a cave bear or the hyenas to, you know, sneak into the cave and grab you at night. So you know, if you were in a place that wasn't entirely safe, you never went completely to sleep,

Anne Danahy 

Right, except as you know, we don't actually become sharper under those circumstances, we go the opposite direction. Well, many different birds migrate hundreds or thousands of miles in the spring and again in the fall. Whimbrels, for example, fly from South America to Canada, and back again, every year. One whimbrel that was tracked, you mentioned in the book, flew 18,000 miles a year. I think it's just really hard to grasp. Is that part of what you find so fascinating about birds?

Scott Weidensaul 

Oh, absolutely. You know, the fact that we're such land bound creatures, and you know, the notion of us traveling 18,000 miles, most of us, under our own propulsion, you know, we can no sooner jump to the moon than do something like that. And even the tiniest birds do this. I mean, ruby throated hummingbirds breeding Pennsylvania that weigh slightly more than a penny fly nonstop 600 miles across the Gulf of Mexico twice a year. And they're not, you know, hitchhiking on the back of a bigger bird or any of that old nonsense. They're doing it on their own nickel under their own power. Little semipalmated sandpipers that are — what six inches long and weigh less than an ounce — take off from the north eastern coast of North America in the Canadian maritimes fly 3,300 miles nonstop over the course of four or five days, to the north eastern coast of South America. That's like a human being running 126 consecutive marathons. And doing it without food or water or rest. You know, I get a little bit annoyed when I hear people comparing birds to human athletes. No, birds leave human athletes in the dust. Some years ago, a runner broke the four hour marathon record and he was he was hailed, I think, with justification as being superhuman, which is true, but that's still distinctly sub-avian compared to what even the smallest migratory birds are able to do.

Anne Danahy 

Well you give examples of what birds bodies go through to be able to do this, to migrate and fly these thousands of miles without stopping. And, as you note, it sounds like something out of a mad scientist lab like a sci fi movie. There's the godwit. You describe what godwits bodies go through for migration. How does that work?

Scott Weidensaul 

Sure. So, we're talking specifically here about the bar-tailed godwit, which is a shorebird, about the size of a pigeon. It has a long skinny icepick bill. And the population of bar-tailed godwits that breed in western Alaska winter in Australia and New Zealand and they get there by flying, you know 7,700 miles nonstop across the widest part of the Pacific Ocean on a trip that can take them up to 11 days. So before they take off from Alaska, in late August, early September, they undergo a phenomenon called hyperphagia, where it's just basically binge eating, they just feed ravenously for like two weeks more than double their weight, they're 55% fat by the time they fly. And at that point, they no longer need digestive system, so they get rid of it in a matter of days, their stomach, their intestines, other other internal organs shrink dramatically, while at the same time, their pectoral muscles, their chest muscles that power their flight increase in mass by 50%. And their heart muscle increases in mass by 30 to 50%. So they're basically getting ripped and buff without exercise.

You know, it's just it's mind boggling stuff, like you say it sounds like mad scientists stuff. You know, now we've discovered that one of the ways that birds are navigating and detecting the Earth's magnetic field is by using a form of quantum physics that was so weird that Albert Einstein essentially disowned it, even though it came out of his own equations. It's called quantum entanglement. And it's the form of quantum physics that supposedly is going to enable unhackable quantum computers, and faster than light communication. But it's going on right now in the eye of a migratory bird allowing it to visualize the Earth's magnetic field as it flows through the night sky.

Anne Danahy 

It's complicated, but is it possible to explain a little bit of that, give us a little bit kind of maybe the big picture view of how that works?

Scott Weidensaul 

Yes, as long as I can give you the disclaimer that I am not a quantum physicist. So within the eye of a migratory birds there are, there's a pigment molecule called cryptochromes, but specifically one called cryptic chromophore. And it's a light sensitive pigment molecule. And as an actually, just within the last couple of weeks, some experimental evidence came out of out of Europe that really pretty much confirms this crazy sounding theory, but a photon of light emitted maybe, you know, 100 million years ago from some distant star enters the bird's eye hits this cryptochrome molecule knocks an electron out of that molecule and into the adjacent cryptochrome molecule, thus linking them in what's known as a radical pair and, and briefly magnetizing them and and what we gather about this is that as the as these reactions are happening, you know, for a millionth of a second, again and again and again and again, across all of the cryptochrome molecules in the bird's eye. It is providing the bird with kind of a smudgy visualization of the earth's magnetic fields a very, very subtle magnetic field that, you know, we can we can detect it with a magnet, but they can detect it with your eye.

Anne Danahy 

One of the other things in your book that I found kind of mind blowing is that there are these masses of birds flying across the sky at night. They actually form bio-scatter on the radar as they migrate in masses in the spring in the fall. Tell us about what's happening. Why are they doing that?

Scott Weidensaul 

Sure. So most birds migrate at night, even the ones that are normally active by day because the night sky is cooler and less turbulent, there's fewer predators. And because they're doing this at night, we just basically have most of us have no clue how many birds are, are aloft in the night sky. I did. I did a research project some years ago along the Kittatinny Ridge between Schuylkill and Berks County, where we were trying to use a combination of forward looking infrared and vertical beam radar to track their migration. And what we were trying to do didn't work. That's not important. What was important was that on one particular night in early November, at the end of the migration season, we had a strong cold front that came through and the night sky was just a washing birds that we could see in infrared and we could see on radar. And our calculations were that there were birds passing over about a 30 mile stretch of the Kittatinny Ridge at a rate of almost 2 million an hour. At the end of the migration season. If we'd been doing this in August or September, it probably would have been six or 7 million birds. So that just gives you a clue of how many birds are up there and yet you can see them on Doppler weather radar. In fact, it turns out completely by accident. The National Weather Service has built the biggest ornithological tracking device in history with the 143 or whatever it is Doppler weather radar stations across the continental contiguous U.S. And the Cornell Lab of Ornithology, there's now enough raw computing power, that Cornell can take all of the input from all of those radar stations on a minute to minute basis. And if you go to their bird cast website in spring and fall, you can see where those birds are migrating and in what number it has, you know, it has a little tracker, minute to minute to tell you that there are 574.6 million birds aloft in the night sky right now that's more than half a billion birds. earlier this spring they had one night with almost three quarters of a billion birds migrating across the lower 48. If we could strip away the night sky and actually see it in real time with our own eyes, it would be the biggest wildlife spectacle in the world.

Anne Danahy 

And you say songbirds actually make noises to make sure that they don't run into other birds. It's like they're kind of like honking their horns.

Scott Weidensaul 

They're like little foghorns. Yeah. I mean, they're they're not migrating incoherent flocks, the way waterfowl or shorebirds do. But there are so many of them in the night sky, that they give these little vocalizations, these little nocturnal flight calls, basically, so they don't run into each other. And that's giving us another opportunity to understand what's up there because each species has an identifiable flight call. And it's taken scientist decades to figure out what species are we making which of these calls if you've got sharp hearing, go outside away from town and away from cars and you know, highway noise. And in spring and fall, you can hear these flight calls. Swainson thrushes sound like spring peepers. Rose-breasted grosbeaks have this little sound like somebody just goosed them on the butt. What scientists are working on now are creating a network of automated rooftop microphones that would record these sounds, feed them into a common database. And they're working on the AI applications that will allow machine learning to tabulate and identify and quantify all of those nocturnal flight calls. I mean, the radar tells us how many birds are up there, but they don't tell us what species. But the flight calls will actually tell us you know what proportion of those flights are Swainson thrushes, gray-cheeked thrushes or Nashville warblers, or rose breasted grosbeaks or whatever. And so we're right on the cusp of kind of opening up a whole new way of understanding bird migration.

Anne Danahy

So Scott, do you have any tips or advice for people who want to see that nighttime migration?

Scott Weidensaul 

Sure, they can use an old technique, an oldie but a goodie called moonwatching. So in spring or fall, like, you know, April in May, or September in October, at the peak of the migration on the night of the full moon, right after the moon has arisen when it's still low in the horizon. Just watch it with a pair of binoculars or a spotting scope. And if it's a if it's a decent migration, right, you will see birds fly across the disk of the moon. And you want to do it right after moon rise, because the lower it is in the sky, the more birds are going to fly through that. You know, that angle that you're looking at? But yeah, you can you can see these only for a fraction of a second, but it's like seared into your retina. And you can actually, depending on the bird like you know, if a Woodcock flies across the face of the moon, it has such a strange silhouette you're like, if you're a birder, you know, "That's a Woodcock." Or a loon or a heron or an owl. I mean, I've seen I've seen owls migrating across the disk and it is a very cool thing and it can make that nocturnal migration vivid. Plus, you can just go on a Doppler weather radar site. And you know, you'll see this blossom of pale green and blue emerging around the Doppler radar sites just after sunset, as all of these birds are lifting off into the night skies.

Anne Danahy 

So birds when they're migrating. So, you talked a little bit about how kind of how they're programmed or how they know how to do that. But they also make these stops along the way on their journey, some of them. And I'm thinking of your work banding hummingbirds, and quite a few years ago, you were in Centre County banding hummingbirds. It was at a couple's home and they were getting something like 1,000 a day. I was a newspaper reporter at the time so I got to do a story on your your banding project. And the banding was to help track the hummingbirds I think they were heading across the Gulf of Mexico for the winter. And they had a lot of hummingbird feeders. But it's still amazing that the birds like knew to stop there and I think you compared it at the time to like a pitstop that that was on the road trip. And I was like, "Oh, time to pull over at the pitstop." They know how to do that.

Scott Weidensaul 

Sure, yes, what's known as stop behavior, and and I think we've only belatedly understood how really important that is for migration, which is  kind of, Duh! You know, you can't drive from here to Florida without stopping at a lot of 7-11s  or WaWas or whatever along the way. Or, excuse me, in State College I should say Sheetz probably, showing my Pennsylvania roots. But, ruby-throated hummingbirds, you've got a brain the size of a Tic-Tac. And yet they know after they've made that flight once or twice, they know all the good places to stop between Centre County Pennsylvania and the highlands of Northern Nicaragua, close to the Honduran border where you know that particular Hummingbird may be spending the winter.

And we see that with regularly with these really long distance migrants, birds again a lot of these shorebirds like whimbrels and godwits that, you know, there's those bar-tailed godwits, they really only stop in three places under global migration. You know, their breeding grounds in Alaska, the the North Island of New Zealand or the coast of Australia where they spend the winter and the Yellow Sea between China and the Korean Peninsula where they stop on their on their way back because they make this huge detour far to the west, because if they flew directly back across the Pacific, they'd be pushing headwinds the whole way. So if you take away any of those important places, the whole migration system falls apart. And so that's one of the real focuses for migratory bird conservation right now is identifying the stopover points and and protecting them the Yellow Sea in China and and particularly South Korea. You know, we've lost about 70% of the mudflats on which these migratory shorebirds depend on. So that's a, you know, a critical and critically endangered migratory stopover. So fortunately, just in the last couple of years, the Chinese government has made dramatic moves to protect what remains of the mudflats there. They've nominated many of the most important for UNESCO World Heritage protection. But it's you know, really very much the 11th hour for a lot of these birds. There's just there's no there's no wiggle room left for them.

Anne Danahy 

If you're just joining us this is WPSU's Take Note. I'm Anne Danahy. We're talking with Scott Weidensaul, a Pennsylvania native and author of "A aworld on the Wing: The Global Odyssey of Migratory Birds." So we're talking about the importance of these places for the birds to stop and the threats that they're under. And you visited the Yellow Sea in China. What was that like when there were those thousands of birds there?

Scott Weidensaul 

It's really extraordinary because you have this enormous migratory system what's known as the the East Asia Australasian flyway. And something like 11 to 13 million migratory shorebirds pass through their birds that that breed from Western Eurasia all the way to Alaska and the Northwest Territories. And winter, you know, in Australia, New Zealand, Oceana across Southeast Asia. So it's like this, the narrow waist of this enormous hourglass shaped migration system. And because so many of the mudflats had been destroyed, they've been they've been, quote, unquote, reclaimed, turned into dry land, basically, the remaining birds have to squeeze into whatever is left, which bad for them. But it makes for a really stunning visual experience. Because you just have waves and waves of tens of thousands of these birds coming in and feeding with just frenetic energy.

We were at a place called Dongling on the tidal flats north of Shanghai. And when the tide goes out there, it was out for like 20 or 30 kilometers, it's just extraordinarily wide mudflats. And so you get out there, you don't see anything. And you're kind of like, okay, what's the point of being here. And then suddenly, from the far horizon, this enormous cloud lifts off and rushes toward you. And within moments, you're surrounded by thousands, or tens of thousands of birds parting around you like water around the rock in a river. And it's just this mayhem and chaos and wings and motion and sound and then they're gone. Again. It's it's just such an extraordinary thing.

I mean, I've been chasing birds all around the world, all my life. And there have been few experiences that that compared to that, but here's the thing. You know, we're still making astounding discoveries, even in our own backyard. Earlier this spring, you mentioned whimbrels, whimbrels are a large another pigeon size shorebird with this beautiful long down-curved bill. Earlier this spring, I had the opportunity on the coast of South Carolina to see a site I thought was born from North America, which is extraordinary nighttime concentration of about 20,000 whimbrels, on a tiny little island, offshore near Charleston, these birds are stopping in their migration from the northern coast of South America all the way up to the Canadian Arctic. And they spent about a month on this little place called Deveaux Bank, fanning out across the salt marshes during the day. And in some cases, traveling as much as 50 or 60 kilometers to feed and then coming back to this little tiny sandspit at night where they're safe from predators, and they're safe from disturbance. And scientists just discovered this a couple of years ago and have basically been keeping it under wraps because it's such a sensitive place that, you know, on which the survival of these birds utterly and completely depends.

Anne Danahy 

So you said that there's some reason for hope. The example of some of the land being preserved in China, I think it was, but then there's other places in the book, you give the example of a seawall being built in South Korea, and that meant that 70,000 of the great knots that's it, they lost their their place to go. So are you hopeful that you'll be getting, that ornithologists are getting this information about what needs to be preserved fast enough to do it as development across a lot of the world goes full speed ahead.

Scott Weidensaul 

Well, yeah, that's the big that's the big question. And whether I'm optimistic or pessimistic, it depends on the day, I think, and what's been in my newsfeed that day. You know, I think at the core, I'm essentially an optimistic person because what's the point otherwise? You know, if you're pessimistic, you're just gonna give up. I think we are developing the tools and the technologies, we need to answer the questions we need to answer maybe just in the nick of time. Like I mean, two years ago, a team of the top ornithologists in North America published a paper documenting that we've lost 3 billion birds in North America since 1970. That's a third of our avifauna has been gone since I got started as a birdwatcher in the late 60s and early 70s. So that's, that's grim, but we know what the score is now. And we're learning where the choke points are. With some of these birds, we know what we need to do.

I mean, the group of birds that are in the biggest trouble are grassland birds like meadowlarks, and bobolinks, and grasshopper sparrows. That's almost entirely a function of habitat loss. Thirty years ago, wetland birds and waterfowl were in the same trouble. And we made the decision as a society to put money and resources and regulation and enforcement into protecting and enhancing wetland habitats. And we made a huge difference. The same study that shows we've lost 3 billion birds also shows that waterfowl and wetland birds have recovered dramatically, so we can make a difference for birds. We just have to have the willpower to do it.

And I think one thing that gives me some hope is, weirdly enough, the pandemic, the lockdowns of last year opened a lot of people's eyes to the beauty and importance of birds. They were stuck at home, we couldn't go anywhere. And yet migratory birds brought the world to our backyards. And it's been astounding to see what a surge there has been an interest in birds. Birds, in particular, nature in general, over the last few because of the pandemic.

Anne Danahy 

Along with the development and habitat loss are the challenges bird face from the larger issue of climate change, including rising temperatures and changes in the seasons. And one of the outcomes is this seasonal mismatch for migratory birds. What is seasonal mismatch, and how does it affect birds?

Scott Weidensaul 

We have to remember when birds are migrating, they're doing it all in a very precise timetable. They need to you know, travel in some cases thousands of miles to get back to their breeding grounds, so that they can find a mate and set up a territory and build a nest and lay their eggs and have their chicks hatch, just when the resources that those that those babies need are going to be at their peak. Now that may be caterpillars in the case of a lot of insect-eating songbirds. It may be arctic insects like mosquitoes and midges in the case of shorebirds whose babies have to feed themselves as soon as they come out … they have to get a lot of bugs. And so their timing, over the course of eons has refined itself so that they're arriving just in the nick of time just when the when the resources are at their greatest. But of course the seasons are changing. Spring is happening earlier in earlier fall is coming later and later. The trees in the forests of the Northeast, the leaves are emerging earlier, the caterpillar peak is occurring earlier. But the birds are making their migration especially these long distance migrants coming from Central or South America. They don't know what the weather in Central Pennsylvania is like year to year season to season. You know their migration timing is set on their internal circadian rhythms in the changing ratio of daylight and darkness known as the photo period. And so what's happening with many of these species of birds, is every year they fall a little farther and a little farther and a little farther out of sync with the seasons.

Scott Weidensaul 

They're arriving when their genes tell them to arrive and when the when the photoperiod tells him to arrive but spring has already sprung. And, you know, we haven't really seen serious impacts on North America's songbird populations yet, but of course in Europe that seasonal mismatch has caused once common species like pied flycatchers to suffer population collapses. And in North America in the eastern Canadian Arctic, where they're getting caught in this climatic whiplash where late winter and early spring have become dramatically colder and snowier. And mid summer has become dramatically hotter. A lot of the nesting shorebirds and waterfowl are just — they're caught between a rock and a hard place. They can't breed successfully up there anymore.

Anne Danahy 

How is climate change affecting birds in Pennsylvania? Is that something we're seeing yet?

Scott Weidensaul 

So we're certainly seeing changes in some migration timing for birds that that migrate relatively short distances like brown thrashers, Eastern towhees, Eastern phoebes, those birds have been able to keep up with the seasonal changes that we're talking about. We're not seeing so much of a mismatch and so in many cases they're coming back up two weeks earlier in the spring and leaving up to two weeks later in the fall. You know, we're seeing changes in migration timing with some species of raptors migrating along the quiddity. region and elsewhere, places like like Bald Eagle and Tussey Mountain in Central Pennsylvania. A lot of the other changes are subtle and harder to get a firm grasp on. You know, how are the dramatically increased intensity of summer thunderstorms, for example, affecting the nesting success of birds? How are prolonged times of drought? How are summer heat waves and heat domes having an impact on those birds? How are winter conditions for birds — because in Pennsylvania, the birds breed here in the summer, but there are also birds that come here for the winter. And you know, how are changing winter conditions affecting affecting those birds? It may be, we know that the centers of winter abundance for hundreds of species in North American birds based on Christmas bird count data have shifted dramatically farther to the north, like an average of about 400 miles to the north over the course of the last couple of decades. And when I think scientists are just now starting to get a handle on teasing out the you know, the effects of climate change, as well as habitat loss and increasing insecticide use, and you know, all these other pressures that are occurring right now that are having an impact on bird populations.

Anne Danahy 

And this topic isn't one that comes up in your book, but I'm just curious if you have any thoughts about it. There's a big question lately about the naming of birds and whether they should bear the names of specific people, in particular people in the past who are racist or pro-slavery, and the American Ornithological Society announced they're forming a committee to look into this. Do you have any thoughts on that?

Scott Weidensaul 

Let me start by saying that I am very much a traditionalist and an institutionalist by nature. But the more I thought about this, and the more I listened to colleagues of mine who are, you know, Black or Brown or otherwise not an old white guy like me, the recognition that, you know, naming birds for people like John Bachman, Bachman Sparrow and Bachman's warbler, who was a virulently vocal white supremacist or even John James Audubon, who was a slaveholder — not something that's, that's widely been acknowledged — maybe isn't the most welcoming way to increase the diversity and inclusion of of the birding world, which is a very, very white, middle, middle and upper class hobby. You know, as a number of ornithologists have come around to saying, you know, why not just give them descriptive names? You know, instead of Kittilitz's Murrelet, which doesn't really tell you anything, except that you got to look up how to spell Kittilitz's every time, call it the glacier murrelet because this is a tiny little seabird that flies 50 or 60 miles inland and lays its eggs next to rock piles in the middle of Alaskan glaciers. I actually think this is a change that's going to happen in the next couple of years. And it's going to roil the waters in the ornithological world and make a lot of people unhappy. But I think at the end of the day, it's probably a good thing.

Anne Danahy 

Well, Scott Weidensaul, thank you so much for talking with us.

Scott Weidensaul 

Anne, it's been a real pleasure. Thanks for the opportunity.

Anne Danahy 

We've been talking with writer and naturalist Scott Weidensaul, whose most recent book is "A World on the Wing: The Global Odyssey of Migratory Birds." For this and other episodes of Take Note, go to WPSU.org/Take Note. I'm Anne Danahy. WPSU.