THOUGH I MOSTLY stay put these days, no longer inclined to move very far beyond my home range, apparently I’m intensely curious about the subject of bird migration, which came up in questions I asked during several favorite podcast interviews in 2019.
The miracle of bird migration is a subject of much intensive study, especially in this age of rapid climate change. Migration actually originally evolved in large part as a response to changing climate, but of a far more gradual nature over the millennia and longer. Now scientists wonder how species will adapt–or if they can–to current faster shifts.
At the end of 2019, Colorado State University, the Cornell Lab of Ornithology, and the University of Massachusetts published research based on analysis of 24 years of weather radar data, showing that the timing of spring bird migration across North America is shifting as a result of climate change.
They saw a strong alignment between temperature and migration timing, especially in the fastest-warming regions. This synopsis on the BirdWatchingDaily.com website gives more detail of their findings.
On my latest podcast, I look back at other things I learned about migration in 2019, from some of my guests. (And in the garden doodle at the top of the page, my old pal Andre Jordan muses on migration, too. Thanks, Andre.)
Read along as you listen to the January 6, 2020 edition of the A Way to Garden public-radio show and podcast using the player below. You can subscribe to all future editions on iTunes or Spotify or Stitcher (and browse my archive of podcasts here).
the basics of migration, with kenn kaufman
FROM KENN KAUFMAN, author of the 2019 book, “A Season on the Wind: Inside the World of Spring Migration.” I was reminded that the word “migration” isn’t a one-size-fits-all concept.
Kenn, originator of the indispensable Kaufman Field Guide series, is one of the world’s leading naturalists and experts on birds. He lives on the west end of Lake Erie, where spring brings millions of birds virtually to his doorstep.
I asked him first about different migration styles, and also about what the trigger seems to be to say “move,” anyhow. A clip from our chat (the full archived show is here):
Margaret: Is there a master plan to springtime bird movement? Do birds fall into some major categories of behavior having to do with their movements in spring, like how far they move or don’t move, and so forth? Are there categories that we can understand as laypeople?
Kenn: There are some broad divisions and a complete range of birds, from those that are totally sedentary to those that travel long distances. There are hardly any birds that just really stay put completely for their whole lives, even birds that we think of as residents, like cardinals, will move around to some extent within a local area.
Then, you have your short-distance migrants that are present, that don’t have totally separate areas on the rangeland. They may get a little farther north in summer and a little farther south in winter. Then, the moderate-distance migrants that may go from, say, Central Canada to the Southern United States for the winter. And then very long-distance migrants that may go from Alaska to Brazil or Argentina, just these astounding long-distance migrations. But, really there’s every stage in between.
Margaret: The ones that go those very long distances, it’s not optional. They have to do that, yes? I think in the book maybe you call it hard-wired, yes? They’re hardwired to have to do that, whereas some of the ones that can move a little, they don’t have to move quite as far. They can move a couple hundred miles or something?
Kenn: Yes, that’s exactly right. The long-distance ones, the hard-wired ones, they’re sometimes called obligate migrants, and then the others that can be more flexible will be called facultative migrants. Most of the latter are the short-distance travelers.
An example would be something like the kildeer [below], which live out in the open field here. Where I am in Northern Ohio, the last kildeers of the fall disappear sometime in early to mid-December, then the first ones come back in February, so it hardly seems worth the trouble. They may only go as far as the southern part of the state before they turn around and come back.
They can vary their timing and their distance, and they may travel … They may come north earlier in a warmer spring. So, they’ve got the flexibility that most birds don’t. [Kildeer photo by CheepShot from Wikipedia.]
Margaret: Right. What are the triggers that say to birds, “Time to move!” Is it just “follow the food”–is it that simple? Or I think there’s … One of the chapters in the new book is called “Creatures of Light.” I think it talks about some triggers having to do with our response as animals, ours and theirs [laughter], to light and so forth. What are the triggers that say, “It’s time”?
Kenn: The ones that we know something about, a lot of them have to do with the length of the daylight, and the birds are really attuned to the timing of sunrise and sunset. As they change with the seasons, the birds will start to move.
It would make sense to think they’re just following the availability of food, but, actually, in fall, a lot of birds will fly south and fly away from habitats that are full of food. They leave before the cold weather arrives, and the timing is set by the change in light levels.
There will be some places near the equator where that wouldn’t work, and where they may be driven more by changes from wet season to dry season. But in North America, the length of the daylight really seems to be the driving factor….
Margaret: Speaking of light, does migration mostly take place in darkness, at night, or are there some birds who move during the daylight hours?
Kenn: That’s one of the fascinating things about it, and one of the things that makes it hard to study is that there are quite a few species of larger birds that do migrate in daylight. Most of the hawks, for example, are daytime fliers. Cranes mostly migrate by day. Ducks and geese may migrate by day or by night.
But most of the smaller birds, most of the songbirds, which are, of course, the most abundant ones, migrate at night. So, they’ll take off just after it gets dark and fly through the night, and then, if they’re over land, they’ll come down around dawn and … Of course, this makes it hard to study what’s going on up there.
Margaret: Do we have an idea of why we think that’s the case? Are they navigating—celestial navigation—or is it because it’s cooler at night? Is there a reason that we think?
Kenn: There’s been a lot of ideas tossed around for why they’re migrating at night. The air masses may be a little more stable then. There may be fewer predators flying around. The hawks are migrating in the daytime [laughter], so nighttime-
Margaret: So, if you’re a songbird [laughter]...
Kenn: Yes, makes a difference.
Margaret: I see. Yes.
Kenn: They do use navigation by the stars, although daytime migrants can navigate by the sun as well.
julie zickefoose and the lessons from her blue jay
THERE’S JUST SO MUCH that remains unknown about migration—even among the most familiar bird species. Take blue jays, for instance. I spoke to WRITER, ARTIST and wildlife rehabilitator Julie Zickefoose in 2019, after reading “Saving Jemima: Life and Love with a Hard-Luck Jay,” her charming story of an orphaned blue jay and Julie’s decision to try to help save it.
Their eight-month relationship opened up many subjects for Julie, including that of elusive patterns of blue jay movement and behavior that she began to look at more closely.
Julie thinks of jays as tiny blue crows—jays are actually cousins of crows, in the Corvid family— and they stay together in bands and they travel around together, like crows. But researchers don’t actually know what they do in many cases, she explained, because they’re so intelligent that you cannot capture them in mist nets more than once.
I see lots of blue jays in winter, I said, as “feeder birds” but far fewer in summertime—and I asked her about their movements, and what we know. Her answer:
Julie: “…We don’t really know what they do when they migrate. We don’t know why they fly east-west, unlike almost any other bird in North America, rather than north-south. Some of them go north-south. Most of them go east-west. Why would you do that in winter? Why would you go west in winter? Does it get better? No….
Margaret: I mean, they don’t migrate far, far, far, do they? Or what are they, partial migrants? Or what are they?
Julie: It’s not really known. They may be facultative migrants, which means they go as far as they need to go to find more food. And because they’re very winter hardy, they aren’t really having to go south to find insects. Do you know what I mean? Since they’re relying on a lot of plant material for food in the winter, like acorns, it doesn’t really mean they have to fly to Costa Rica to find katydids.
The way I would describe what the birds in my yard seem to do is they make a circuit and I became used to seeing a certain flock of birds reappear every two to three weeks. They would stay for a few days and then leave and another bunch would come in and replace them.
and what about the movements of sparrows?
In the complete show with Rick, we talked about learning to identify sparrows; about the sparrows that don’t look like sparrows at all–the juncos and towhees–about how particular birds are built for migration (or not), and more.
Rick told me that taking a closer look at a species’ wing shape and tail length can tip you off to its migratory capability. The discussion started by my asking if all sparrows were migratory, or if as a group they had that or any other trait in common, and here’s what he said:
Rick: They are not all migratory. Many of them are strongly migratory: savannah sparrows, American tree sparrows move hundreds of miles in the spring, and then hundreds of miles back south in the fall. Their biology is quite varied, some of them are secretive and solitary, except in the breeding season. Others are extremely social most of the year round. What they do all have in common is diet.
Margaret: Ah, O.K.
Rick: During the warmer season, especially when they’re breeding and need to supply the young birds with protein, sparrows will switch over to an insect diet. Our birds here in temperate North America will then switch over to eating seeds in the wintertime. And that’s why feeder watching is such a great exercise for the sparrow fan, because sparrows spend the winter relatively far north, I’m in New Jersey. The sparrows that winter up here eat seeds all winter long, and that includes sunflower seeds and millet from feeders. So it’s a great thing on a cold winter’s day to sit down with a cup of hot chocolate, put your feet up, and watch the sparrows at the feeders.
Margaret: I think early in the book you talk about observing or inferring from the shape of the wings, the physiology of the birds, the way they’re built, in certain species, that they’re shorter-distance migrants than longer-distance migrants, and so forth. Can you speak to that? Do you know what I’m referring to?
Rick: Yes, that’s right.
Margaret: O.K., because that sort of was interesting to me. A light bulb in my head was like, “Oh, wait a minute, you could even see in their physiology some … you could extract and say aha, this one’s really built for this or that.”
Rick: Yes, that’s exactly right. The sparrows that tend to be very short-distance migrants, and tend to spend most of their time deep in the dark thickets, generally have very short wings and very long tails. The short wings, because they don’t need to fly that much, the long tails because when they do fly, they need to be fairly maneuverable so as not to bounce into a branch and beam themselves. Sparrows—and this is a rule that pertains to other birds, too—sparrows that are more strongly migratory tend to have longer, more pointed wings.
It means that they are better suited for long-distance flight. And one thing that I really love when I’m looking at sparrows, those that spend most of their time on the ground in the open have a set of feathers on the wing called the tertials (just one of those birder words that we use), that are very long, and cover all or most of the rest of the folded wing to protect it from the sunlight, so that those feathers that are used for flying are shielded from the deleterious effects of the sun.
So, you can actually deduce, as you say, quite a lot about the life habits of a bird by looking at the relative structures of its wings and tail.
science is good, but don’t forget the awe
BACK TO MY CONVERSATION with Kenn Kaufman for a minute, toward the end of which he made a very important point: No matter how much you study a phenomenon like migration, no matter what new studies come out explaining what aspect of it … Don’t forget to be awestruck. Here’s that snippet:
Margaret: We humans learn more about migration lately, partly thanks to advances in technology, tracking devices, and radar, whatever. You give an example in the book of this “champion thrush” that was tagged with a device and then observed to fly non-stop, I think, across the Caribbean and all the way to Canada. Again, non-stop, pretty amazing.
In sharing that anecdote, you then write, “I love science, and I hate it.” Then, you say, “In a way, we know more about the birds’ travels than they do.” Tell me a little bit about that part of the story for you.
Kenn: Well, I was opening up there and admitting the ambivalence I have about this. I’ve spent so much time reading scientific and technical works [laughter], dozens of technical volumes and hundreds of scientific papers, to try to understand the science of it. But, I don’t ever want to lose sight of the fact that we’re witnessing something here that’s just … It’s magical. It’s a miracle, and it should be just a total source of wonder.
I find that the more facts that I learn about the migration of birds, actually the more wonderful it becomes. Knowing more about how they do it doesn’t make me any less impressed with the fact that it happens at all. I really feel like it’s this massive, worldwide miracle that happens twice a year, and I hope I’ll never get over the sense of wonder at it.
It just seems sad when sometimes people will take something and make a very scientific analysis of it and try to be dry and formal and technical, because they feel like they have to do that to be scientific. I think the best scientists I’ve met have never lost their sense of wonder, almost a childlike-
Margaret: Yes, awe.
Kenn: … amazement and wonder at what we see out there.
sometimes you needn’t go far: a chat with margaret renkl
NOW, I CAN’T DO a best-of show about migration without mentioning one of my very favorite books of 2019, “New York Times” Opinion columnist Margaret Renkl’s memoir called “Late Migrations: A Natural History of Love and Loss.” It’s not about birds, exactly. It is a book of short essays—some about formative people in her life, and some about nature and some about both—that were written as a response to her grief about the loss of her mother and also her mother-in-law. From our archived show together (listen in its entirety) here’s her description of the book:
Margaret Renkl: And at the same time I was writing, I was spending more time looking out the window at the natural world of my backyard, in part, in response to the changes my neighborhood was undergoing. But in part because I found that that focus helped me with the grief, it helped me see that life and death are just … that cycle is very natural, and nothing to fight or to fear. My mother was 80 when she died. My mother-in-law was 81. These were not tragic or untimely deaths. It was part of the natural order of things. And it helped me, it was a great comfort to me.
And so after I had done a little pile of both kinds of essays, I started to see that really they were connected in fundamental ways. The creatures in my backyard felt like family. And what was happening to the natural world, both in my own neighborhood and to the planet in the form of climate change, was a source of great grief to me. So I began experimenting with ways to combine them, and what ultimately resulted was “Late Migrations.”
MAYBE THE MOMENT in my bigger conversation with Margaret Renkl that I loved most: Where we agreed that you don’t necessarily have to go anywhere to find enough to fill a life. Here’s that part of our chat:
Margaret Roach: And I think that was, again and again in the book, what really spoke to me, because I find such solace … People ask me, what am I doing, because I live alone in a rural place, a town of 300, and they say, “What are you doing?” I say, “I’m looking out the window.” Do you know what I mean? That’s-
Margaret Renkl: Mm-hm. Mm-hm.
Margaret Roach: That’s where I get informed all day long, is by looking out the window. And I felt like you also find great inspiration and solace in that.
Margaret Renkl: There’s a line in, I think it’s in “Walden,” but it might just be in Henry David Thoreau’s journals, and I know I’m not quoting exactly, but he says, “I have …” or something like, “I have traveled extensively in Concord.” And I’ve always loved that line because it’s exactly what I think is true.
Margaret Roach: [Laughter.]
Margaret Renkl: I mean, I’m not in any way knocking grand traveling as a way of understanding the world, but I think there is an equal way of understanding the world by knowing very well your own little place in the world.
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MIGRATING OR STAYING PUT…may you have the next new year ever, and don’t forget to figure in plenty of time to just slow down and watch. And of course to keep listening!
Thanks to all of you for your support of the show in 2019, and don’t forget to say thanks to the smallest NPR station in the nation, Robin Hood Radio in beautiful Sharon, Connecticut, where my beloved neighbors Marshall Miles and Jill Goodman make it possible for me to produce it and share the weekly segments with you. You can thank them with a tax-deductible gift at robinhoodradio.com/donate. Happy New Year!
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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 10th year in March 2019. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the January 6, 2020 show using the player near the top of this transcript. You can subscribe to all future editions on iTunes/Apple Podcasts or Spotify or Stitcher (and browse my archive of podcasts here).