fun facts about birds: ‘birdpedia,’ with chris leahy

HOW MANY BIRD SPECIES are there in the world and how many individual birds? And how do you even try to count? Do bird sweat, and how is their eyesight or sense of smell? What makes some eggs solid blue and others speckled brown, or are any two species’ eggs the same size and shape and color? Well, these are just a tiny fraction of the disparate and fascinating questions answered in the new book called “Birdpedia” by Christopher Leahy.

Christopher Leahy retired in June 2017 from a 45-year career as a professional conservationist with the Massachusetts Audubon Society, and was for 16 years director of its Center for Biological Conservation. He’s the author of numerous books, most recently, “Birdpedia: A Brief Compendium of Avian Lore,” our topic today.

Plus: Enter to win a copy of “Birdpedia” (affiliate link) by commenting in the box at the bottom of the page.

Read along as you listen to the July 12, 2021 edition of my public-radio show and podcast using the player below. You can subscribe to all future editions on Apple Podcasts (iTunes) or Spotify or Stitcher (and browse my archive of podcasts here).

‘birdpedia,’ with christopher leahy



Margaret Roach: You’ve written many books, maybe this is about your eighth or something, I don’t know. I was trying to count.

Christopher Leahy: Well, I guess it depends on what you count. I’ve had of a number of what might be called major books the book from which this is, I wouldn’t say derived exactly, that’s not quite correct.

Margaret: Distilled.

Chris: Yeah. Starting back in 1982, I wrote something called “The Birdwatcher’s Companion.”

Margaret: Yes.

Chris: And that was re-issued then at the urging of the American Birding Society by Princeton University press in 2004, I think.

Margaret: Yeah.

Chris: And so, yeah, that. But I’ve also written some things on insects and I’m interested in natural history in general. But with birds as a specialty, certainly.

Margaret: Yeah. Well birds—like you, birds like bugs [laughter]—so that’s good. You like birds and insects and they like insects, too. It strikes me that this little book, this might’ve been fun because it’s this eccentric compendium of things about birds. How did you ever choose what made the list? You were just saying distilled from all this past knowledge, but it must’ve been hard to figure out what goes in.

Chris: Well, I think you sort of nailed it when you talked about the qualities that you see in the book. This book is meant to be an introduction to people who… Birding’s become much more popular than it certainly was when I was a kid, when it was looked at vaguely suspiciously. And yet there are millions and millions of people who are like, “What? Birds? Why are these people looking into the trees?” [Laughter.]

And so this book is meant to show the incredible diversity, not just the diversity of bird species, although that’s certainly a draw, but the diversity of ways in which human life is connected with bird life. We eat birds, and we worship birds, and we have worn birds, and etc. etc. And we occupy the entire planet with birds.

Margaret: Yes.

Chris: And so there are so many aspects. I have entries on poetry and painting and things like that. And I think a lot, it’s like, “Who knew?” And so, yes, it was helpful to have “The Birdwatcher’s Companion,” because it was clear to me that what I didn’t want in this book, which is in that book, is descriptions of every bird family in North America.

Margaret: Right.

Chris: I flatter myself that I can write about subjects like that with a degree of lightness and wit, but this was not meant to be comprehensive. It was meant to be a teaser and to have people go, “Oh, that’s interesting.” And get deeper into it.

Margaret: Yeah. So I should say as part of a series of -pedias from Princeton University Press that already includes “Fungipedia” [affiliate link] and “Florapedia,” with more to come. So maybe we begin, briefly at least, as you do the book, with how many birds are there and the challenge of trying to ascertain this—individual birds, and then as well as the total number of species.

Chris: Right. And that gets very much to what we were talking about, about the challenge of some of these things. There are certain figures about birds that we can nail down certainly in terms of their populations. In terms of just to get rid of the species concept of the moment, there’s about 10,000 plus species of birds as determined by ornithologists on the planet today. So that’s species, and that’s only a tenth of the number of species that have occurred throughout bird-dom with evolution.

But in terms of individuals, of course, we’re an entirely different order of magnitude. And of course, even people that are not specialists or anything can kind of look out in their backyard. And if you think about, “Oh, counting of the different individual birds in the world”—very, very daunting.

But there are a couple of places where you can start and actually can know how many birds there are explicitly, or come to a very close estimate. One of them is very rare birds. So for example, let’s take whooping cranes. We know that as of 2021, there are 76 individual whooping cranes on the planet.

Margaret: Oh!

Chris: Which of course is sad, but true. One of the interesting things is that only 16 of those were born in the wild, and the rest of them were captive-reared. And that’s a whole other subject or whatever. But that’s one where we can nail that down. And there are other of course, very, very rare birds where we can say similar things.

The other kind of class of birds is quite different where we can get quite an accurate number is, say, colonial seabirds, which nest in very compact colonies in the open, as in open islands or rocky cliffs. So think about gannets or terns or gulls or something like that. These are colonies that could be photographed from the air, and then some poor graduate student is probably assigned to “one, two, three”—how many pairs of gannets there are. [Laughter.] And that’s another way to come to a fairly accurate sense of how many individual gannets or turns or whatever it is there are.

And the other one I should mention is chickens [laughter.].

Because they’re domestic birds, but they’re, they’re real birds and they’re of course derived from wild species. So we know, but even there it’s a little bit sketchy that there are between 19 and 50 billion domestic chickens on the planet.

Margaret: Oh.

Chris: And that’s compared to 7.8 billion people. So if the chickens ever decide to take over, we’re in big trouble.

Margaret: Definitely, definitely. They’re so bossy [laughter].

Chris: They are, they are. Yeah, even if they’re in their current sense. And then after that, we definitely get into estimate time.

Margaret: Right.

Chris: And various ornithologists and people have taken stabs at this. There’s a very industrious French scholar who really made a very strident effort to come to a good estimate of how many songbirds were in Finland. And I can’t remember what that number is, but the numbers that I’m about to give, come from that kind of thing, where we think, “O.K., we have a pretty good sense of this, so let’s extrapolate,” and whatever.

And what we come up with then is an estimate that says, and now we’re talking wild birds now excluding the chickens, 100 billion wild individual birds in the world. And that’s give or take 100 million or so.

So that’s as close as we get at this point.: And then bringing that down a bit to the U.S., the estimates are from 5 to 6 billion in the U.S.

And then one of the things that actually is in “Abundance,” which I think it’s the first entry in the book, is I talk about what everybody pretty much agrees is the most abundant native wild bird. Not native here, it’s native to Africa. It’s something called the red-billed quelea [above]. And the red-billed quelea is a tiny, but quite brightly colored (the males at least), red and black bird, a seed-eating bird of central Africa.

And it occurs in swarms of millions. And so the connection, the metaphor, the simile with locusts is not inappropriate. And as such, and again, this is a native species, this is not something that escaped and is an alien or something, as such it is a crop pest in many places. And people living in a given area dread an invasion of these things, because they are grain eaters and they can devastate-

Margaret: Right, of course.

Chris: … a crop or something like that. And the estimate of that, so this is supposed to be the largest population of native songbirds in the world. And that number is 10 billion, estimated at 10 billion.

Margaret: Wow.

Chris: So that’s a lot of little queleas eating your crop. Yeah.

Margaret: And so counts come from human observations. Of course, some of them are these more formal scientific context, and so we’re trying to estimate populations. And I loved also that on the other end of counting birds, you have some sections on birdwatching or birding, depending on where we are and what we want to call it. And on the watchers and so forth, and the styles of watching and what’s observed and recorded. And there was a new word to me in there, which was “twitchers.” Twitchers.

Chris: [Laughter.] Twitchers, yes.

Margaret: Tell us what a twitcher is.

Chris: O.K. Well, this is British terminology.

Margaret: Yeah.

Chris: And the North American synonym for a twitcher is a lister. And I have a section in the book, an entry in the book, that talks about listing, and how one of the many morphs, if you will, of the birdwatching tribe—of which there are many. Some people feed birds and that’s their passion, some people study bird behavior and that’s their thing. But quite a lot of people look at birds as a game or a sport or something in terms of how many birds they can see.

Margaret: Yes.

Chris: I think a lot of people are aware of the concept of a life list, which is how many different species of birds one has seen in their life. And this involves, for people who can afford it, traveling internationally. I, for many years was a guide on international birding trips, taking people all over the world basically. And a lot of them were keeping their life list. But I have an entry in the book, which talks about perhaps the extreme that this can be taken.

Margaret: Yes, you were a little extreme, Chris, I think [laughter]. You have many lists.

Chris: That was quoted from an article in the American birding association of a person, and I cite him, who absolutely loves keeping as many lists as he can think of.

Margaret: Right. The birds this month, the birds in the yard, the birds in the state, the birds in the county…

Chris: Exactly. And he’s passionate about that. And I get this at some level. I started seriously birdwatching when I was 11 or 12. And definitely at that age, oh, it was about seeing as many different kinds of birds as you could. And I still keep some lists, although not as many as that gentlemen.

I also pointed out that though it was a pretty comprehensive list of lists, as you indicated, I know some birders who keep yet more. For instance, some people keep track of the bird species they’ve heard from bed [laughter].

Margaret: Oh my goodness. Well, my favorite one on that person’s list was “bell ringers.” A list of bell ringers: birds seen in all months of the year. So that’s good. I liked that in a way.

Chris: It’s all about fun really. And twitcher, again, is the British synonym, but it has a touch… I’ve spent a lot of time in the U.K. because our sister organization, the Royal Society for the Protection of Birds, I’ve gotten to know a lot of people there and led tours with them and had gone birding, etc. And twitcher there has a slightly contemptuous tone to it [laughter].

Margaret: Of course, yes.

Chris: It’s a serious bird person. All British birders used to, I think they’ve moved into the American fun realm a little more these days. But they all had notebooks, they made sketches of rare things that they would need to submit to make sure that they were approved and all that kind of stuff. And the idea of somebody who just got in their car and drove across the country to see some rare North American straggler, well, they were twitching-

Margaret: Right. To add to their life list.

Chris: A twitch in England is what we would call a check mark.

Margaret: Check mark, yeah. Yeah, yeah. So my yard list, if I were to fall that person’s example and have a yard list, maybe I see 70-something species of birds in my yard.

Chris: That’s pretty good.

Margaret: So it wouldn’t be that big a list, but it’s a big enough list. And those are my friends, those are the birds I feel that I “know.” Not just because I can ID them, but behavior. Because what interests me is more than putting someone on a list and saying, “Check, check, check. Twitch, twitch, twitch.” I love to watch how they’re different, the species, and sometimes the related species, have different behaviors and so forth. And so for instance, caching of seeds or other foodstuffs, I just love it. And I love to watch the titmice and the nuthatches. And I love that. And so maybe just real quick, tell us what caching is.

Chris: O.K. Let me just…

Margaret: Ha! You’re going to look on page 46.

Chris: No, I’m going to look because there’s some numbers that I want to get right.

Margaret: Oh, O.K.

Chris: But generally definition wise, caching is storing food by birds—well, not just by birds—but for future use. And that’s something that certain bird families especially do. You mentioned chickadees, nuthatches and those things.

Some of the champion cachers are in the crow family. That is to say, jays and nutcrackers, not particularly crows themselves, but that’s a family where the genius cachers come in. And they do this in a way that… Again, the numbers connected with this are quite eye-popping. A technical point, how they do this: They basically take a seed or a bit of potato chip or whatever they want to cache for the future, and they’ll stick it in a tree crevice or a rock crevice or bury it in the ground. And they have special enhanced saliva glands that produce a very sticky form of saliva that they then attach to this item so that it doesn’t fall out or whatever. So there’s actual physiological help for this.

Margaret: Amazing.

Chris: So yeah, just to give you an idea of the scope of this, I’m just reading from the text here from the “Caching” entry, it says Clark’s nutcrackers, which is a bird of our Western mountains basically, for example, “can store more than 30,000 items in up to 2,500 locations over a season, in some cases traveling more than 15 miles and are able to recover about two-thirds of them as much as 13 months later.”

Margaret: And this is why I love birds and their behavior, because I can barely find my glasses some days even though I have them on [laughter].

Chris: Yes, I’m there too.

Margaret: I love it. I love it. So then there’s another one, mobbing [below], which people have probably seen, sometimes even a smaller bird goes after a bigger bird in the sky and there’s lots of squawking and so forth. I loved reading that it might have a benefit to help the adults teach their young who the predators are.

Chris: Yes. There’s a lot of controversy. Nobody can actually converse with the birds about this. If you’ve ever seen it, which you obviously have—and I always find it especially intriguing to watch like a screech owl or something. And the whole songbird community comes out to harass this bird, and the poor screech owl always looks like, “Oh gosh, not again.”

And so what seems to be the case is one of the things that’s happening is the bird communities, especially with smaller birds in the case of the screech owl that I just mentioned, what they’re basically doing is there may be an element of trying to chase this bird away, but what they seem mainly to be doing is alerting the bird community that, “Oh, there’s a predator present, watch your back.” Just showing that he’s there. And then the fact that these birds do scream at him, as it were, and dive at him, sometimes actually make contact.

And often the bird will take off like, “I’ve had enough of this.”

The aspect that you described is one that, again, it’s circumstantial in some sense, but there’s some evidence to support it. And that is that in cases where birds are, are reared in captivity and then re-released to the wild, there are a couple of cases in which it is believed that because the young birds were not “schooled” by their parents with things like this mobbing behavior, that they were unprepared to respond to predation in the wild.

Two cases that have been mentioned are whooping cranes, to come back to those, but also the thick-billed parrot, which is a species that used to occur in Southwestern U.S. and became extinct. And as they tried to reintroduce it, they were just wiped out by predators. And they thought that possibly it’s because these birds were unskilled at recognizing what to watch out for.

Anyway, the mobbing thing, I’m always struck by the fact that things are mobbed where… I live on the coast and so smaller birds, whatever, will often mob herring gulls and things. And the herring gulls in no case would ever go after a lot of the birds that mob them. But there’s obviously a general response to a certain size of bird or kind of bird that triggers this, which I find fascinating.

Margaret: Yeah. It’s been really hot lately where you are, where I am ,and a lot of parts of the country even worse. So do birds sweat, or how they cool themselves?

Chris: Yes. Birds do not sweat, which is probably a good thing. But obviously, they do have the same problems with overheating that we would. And so they have no sweat glands, is the physiological answer to that. So they have to get rid of excess heat by other means.

One of the ways they do this is by panting. And this is probably something that you don’t notice unless you’re looking for it. But if you went to, well, almost any place in this current heat wave we’re in, and looked where they were gulls or any kind of birds, because all birds do this, you’ll often see them being very still with their bills open. And what they’re doing is releasing excess heat through moisture, through moist air, which has the same effect as sweating. The other technique that certain birds use is what the ornithologists called gular flapping, or something like that, anyway.

Margaret: Flutter, I think it was flutter. Gular flutter? Yeah.

Chris: Very good. Birds like cormorants have a fleshy throat patch, and this is in some cases extended into a flap, and they can enlarge that to a certain extent. And then they vibrate that, and that has the same effect of the panting, of getting rid of the excess heat.

And they also have good control of their circulatory system. So they can shift body heat into extremities, unfeathered extremities, like feet and whatever. And again, get rid of unwanted heat.

Margaret: And so in the winter, you’ll see them fluff up to stay warmer, but then do they compress their feathers?

Chris: Indeed.

Margaret: In the heat?

Chris: That’s quite correct. They do indeed. If you think of what they’re doing in the winter, it’s like us putting on a down jacket. They have these multi-layers of different kinds of feathers, and there’s a very distinctive down layer. And that’s very important for keeping birds at the right temperature. So yes, they fluff and do that down-jacket thing in the winter. And then the opposite in the summer is putting on a light sweater or something, or a shirt or something. They compress those feathers so that heat doesn’t build up.

Margaret: I wanted to ask you: Was there something that you want all of us to know the most in the book? Was there a favorite thing or a real aha for you, maybe? Something that delighted you to be able to include particularly? Because there were so many for me, I could just make a list [laughter].

Chris: That’s nice to hear. I guess I would have to answer more in the collective. I’ve been studying, although I wouldn’t have thought of that when I was 12, but paying attention to birds for a long time. So in terms of individual facts, sure, there were little factoids like some of the ones we’ve discussed.

But for me, to be reminded again of how interconnected people and birds are, not just that there are lots of birds around all the time and lots of species and you can check them off, but that they are intimately connected with our culture. And that once you have some understanding of how close that connection is, it just offers this wonderful opportunity for not only learning new stuff, but having fun and things that make you laugh, which birds seem to be unique among wild animals of having that broad spectrum of connection.

Margaret: I think for me, part of it’s because they stand on two legs.

Chris: Uh-huh?

Margaret: I know that sounds crazy and I’m identifying with them, but I do identify with that many animals have four legs and fur. I know they have feathers and we don’t, but there’s that standing on two legs thing that somehow it gives me an affinity to them, but that’s my crazy thought [laughter].

Chris: No, it’s whatever. I love, by the way, your comment, when we were emailing or whatever about your crested flycatcher and the snakeskins.

Margaret: Oh, I’m crazy about bird’s nests and we’ll have to have a whole other conversation about that, about bird’s nests and how the heck does the new generation know what its species’ nest design and materials, the architecture and the materials are. That’s a whole fascinating world in and of itself. Well, I’m so glad to finally really meet you a little bit. And I’m having such fun with the book, “Birdpedia,” and thank you so much for making the time today and stay cool. Compress your feathers, Chris.

Chris: What’s that? Yes.

Margaret: Compress your feathers.

Chris: O.K. Thank you, Margaret.

(Illustrations by Abby McBride from “Birdpedia,” used with permission.)

enter to win a copy of ‘birdpedia’

I’LL BUY A COPY of “Birdpedia: A Brief Compendium of Avian Lore,” by Christopher Leahy for one lucky reader. All you have to do to enter is answer this question in the comments box below:

Is there a bird behavior or something about birds that either fascinates you or that you wonder “why” about? Tell us.

No answer or feeling shy? Just say something like “count me in” and I will, but a reply is even better. I’ll pick a random winner after entries close at midnight Tuesday, July 20. Good luck to all.

(Disclosure: As an Amazon Associate I earn from qualifying purchases.)

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MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its 11th year in March 2020. 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 July 5, 2021 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).

  1. Virginia Jenkins says:

    Why do goldfinches gather in a crowd at my feeders and red finches mainly only 1-3.
    Pacific Northwest

  2. I wonder about how long it takes turkey vultures to produce chicks, the mating, then the laying of eggs, the hatching, then the fledgling of the baby birds?

    We live in the woods in Maryland on the Sassafras River and there appears to be a nesting pair in an oak tree on our property. Because a nearby cherry tree has leaves that cover the nest site it is hard to observe what is going on. There appears to be much flapping of wings and bird talk ( sort of a raspy sound).

  3. Marjorie says:

    I sometimes see birds ‘wipe’ their beaks as they eat…similar to us or another reason entirely?
    Count me in!


    Crows behavior I stayed with my sister for 10days. At close to sunrise the crows would come into the trees around her home and would cry for a few hours this is very loud then they would disperse however one or two would remain and continue squawking all day on and off. We started to do some research about why they do this and couldn’t come up with any good answer. There are also a couple of hawks that seem to always be around the area as well. We wondered if there was any relationship between the two things.
    Thanks Barb Bullemer

    1. Tricia says:

      I am fascinated with the hummingbirds that come to my patio garden and LOVE my nasturtiums! I did not know they were so attracted to them. I do wonder if and how birds like hummingbirds know which flowers have nectar as they only go to a few flowers not all of them.

  5. Nancy says:

    I am most interested in the behavior of my garden birds that I see every day. I love how they interact with others of the same species and of different ones too. Family members of my crows play keep away and cuddle. Sometimes I can have 4 different species of birds in the bath together getting along just fine and other times one guy just insist on having it all to himself. Some birds stand up for themselves while others always give way, and it’s no necessarily depending on size. Young birds are so clueless it seems. I try not to anthropomorphize their antics but they are so dear to me I suppose I do!

  6. Carolyn says:

    Why are mockingbirds so aggressive? We have several backyard birds that build nests in all the things I hang for them, but those mockingbirds are scaring them off. I want them all God’s creatures to live in harmony and peace.

  7. Marsha says:

    I want to know more about where the birds come from and go that are migrating through or winter elsewhere like the swans and eagles and osprey

  8. Jane R says:

    I was recently wondering about bird behavior because there’s a robin in my yard that is unable to fly. I’ve been reading about stress, molting, preen oil and head scratching, among other things. There is always room for another bird book in this world!

  9. Marie says:

    I’m happy to say, there are a lot of birds in my suburban neighborhood and a surprising number of species. One thing I’ve noticed through observation (and you called it mobbing) is that predator birds (various types of hawks and owls) are often hassled and driven off by groups of smaller birds. The smaller birds will gang up, regardless of species. A few weeks ago, I watch a large raven getting into a squirrel’s nest. The mother squirrel tried her best to fend off the attacker, charging the nest and chittering at the raven, retreating when the raven flew at her. A group of about 10 blue jays, sparrows, robins, and finches joined in to hassle the raven and defend the squirrel nest. It was fascinating. The raven took off with several smaller birds in hot pursuit. Too late for some of the squirrel babies, I’m afraid. I watched the squirrel howl and cry (yes, she seemed to cry!) for 15 minutes and then one by one, move to 2 remaining babies to an alternate nest further into the woods. Then last evening sitting on my deck, I hear all the birds sounding the alarm. Minutes later, a great horned owl flies by with a blue jay and a gang of sparrows in hot pursuit. It’s interesting behavior.

  10. Barbara Muhlfelder says:

    On the advice of CT Audubon we have taken down all our bird feeders due to the reported deaths of songbirds in the Mid-Atlantic area. As the cause of death is not known nor if it is contagious, we are urged to not encourage congregate feeding. I MISS THEM! I can watch birds from seats in the garden, but not having them fight at the nearby feeders or gaze upon us eating breakfast while they eat at the window feeder is downright sad and lonely.

    Count me in – this book sounds terrific!

  11. Lori Beitler says:

    I’ve been watching a Robin outside my office window as she made her nest and feed her babies. There was another nest (another type of bird – much smaller) nearby that she kept attacking and trying to get to the babies. I know I shouldn’t have but I kept shooing her away. I’ve never seen that. Is it a common occurrence?

  12. Jodi says:

    I have a hummingbird at my feeder lots and all of a sudden it will just start flying back and forth in a straight line . It does this for 9 or 10 times and then goes back to the feeder. I don’t know why it doing it

  13. Autumn Garcia says:

    I am totally fascinated by how the red-tailed hawks in my area glide on/in the air currents… really, I am totally jealous also!!

  14. E. Hoskinson says:

    Fascinating in that, at least where I am located, the birds sing, but with different tones, with an array of notes, that make them an entity unto their own. A listener is usually certain that song emanates from a bird, but which species? A dog’s bark, a horse’s neigh is identical among all the breeds, yet a bird’s song is an arrangement of notes, tones, tempo and rhythm that no other bird can match (well, almost no other bird). I wonder if this is unique to the bird world, or do other groups reflect that variety?

  15. Mary Farrell says:

    I love watching the hummingbirds at the honeysuckle, the red salvia, and many other flowers depending on the time of year. Interestingly, the goldfinches are often in the honeysuckle on the arches. I’m not sure if there may be insects in the vines that I’m not aware of, or if they’re after nectar.

    1. Kathleen says:

      I’m so interested in the relationship between birds and plants. I’m in a new landscape, planting natives and watching (and listening) to the birds who are moving in. Fascinating.

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