The Dazzling Rufous Hummingbird, Threatened By Climate Change
The Rufous hummingbird has a reputation as one of the continent’s most tenacious birds of its size. Weighing less than a nickel and topping out at three inches long, it’s migratory journey is one of the world’s longest. Each spring, just as flowers start to bloom, it will travel nearly 4,000 miles—from Mexico to Alaska.
Yet climate change is taking its toll on even these tenacious birds. The population of rufous hummingbirds, one of the most common hummingbird species in the U.S., is decreasing dramatically. And the Rufous may soon join the list of 37 hummingbird species currently threatened with extinction, according to an analysis by BirdLife International.
Jon Dunn, natural history writer and photographer set out to document as many of these remarkable bejeweled birds as he could before they are gone. He joins Ira to talk about their shared fascination with hummingbirds and his new book, The Glitter In the Green: In Search of Hummingbirds.
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Jon Dunn is a nature history writer and photographer based in Shetland Isles, United Kingdom. He’s author of The Glitter in the Green: In Search of Hummingbirds (Basic Books, 2021).
IRA FLATOW: This is Science Friday. I’m Ira Flatow. I have two bird feeders in my backyard. One stocked with birdseed, another filled with a syrupy solution– four parts water, one part sugar. That second one, my favorite, is designed to attract hummingbirds. I’ve had my hummingbird feeder in my yard for years and it almost feels like the same birds keep returning to sip nectar from year after year. And every time I catch one hovering nearby, it’s exciting.
My next guest, I think, shares my fascination with these bejeweled birds. In fact he spent several years traveling around the Americas photographing all 300 species. And he’s documented that journey in a new book. John Donne, natural history writer and photographer, author of the book The Glitter In the Green, In Search of Hummingbirds. Welcome to Science Friday.
JOHN DONNE: Hi Ira. Thanks ever so much for having me on the show.
IRA FLATOW: Do you have a theater in your backyard?
JOHN DONNE: Well I live in the Shetland Islands, so I’m halfway between the Scottish mainland and Norway. So I don’t have hummingbirds, but I do have feeders for all the other birds.
IRA FLATOW: Well let me begin right with that, because you write in your book that hummingbirds are native to the Americas. Why are there none where you live?
JOHN DONNE: Well if you’d seen the weather in the last week you’d perhaps understand why. Here in Shetland we’ve had blizzards. It’s still winter here. Originally hummingbirds didn’t actually evolve in the Americas. They’re from Europe. The oldest fossils, hummingbird fossils, which have been found in South America are around one to two million years old, which sounds pretty old. But in 2004, a German paleontologist, a guy called Gerald Maya, found a couple of hummingbird fossils which had been dug up from a clay pit in Germany. And they were around 30 million years old.
So the original ancestral hummingbirds actually evolved in Europe. And at some point they crossed into the Americas. And once they got to the Americas in the Andes were rising, they found themselves in, I guess, what was hummingbird heaven. But what we don’t know is in the intervening 30 million years what happened back in Europe. You know they became– it would have been an extinction event back here. It must have got very cold and unsuitable for them, but thank goodness they’d found a way to you guys.
IRA FLATOW: Not only have they found a way to us over here, you talk about journeying to a small volcanic island some 400 miles out into the Pacific to track an endangered hummingbird. So they’re even out there in the Pacific.
JOHN DONNE: Yeah they certainly are. And of course in the Caribbean as well. So really, I mean well, goodness, they’re found from Alaska in the far North right all the way down to Tierra Del Fuego and the southern tip of Argentina, and Chile. So they’ve conquered every imaginable habitat found throughout the Americas, from deserts to above the tree line, high in the Andes, and as you rightly say out on remote Pacific Islands and in the Caribbean as well. So they’re really tenacious and adaptable birds.
IRA FLATOW: And boy can they fly. You talk about a very famous hummingbird, rufous that flew 3,500 miles from Tallahassee to Alaska, the longest known migration of a hummingbird.
JOHN DONNE: Yeah that’s right. I mean, and more than that even. I mean three and a half thousand miles is a heck of a migration by any bird standard. But length for length, it’s the longest bird migration of any bird in the world. I mean the most famous long-distance migrants are arctic terns, which migrate every year from the Antarctic where they spend our northern hemisphere winter up here to the northern hemisphere up to the Arctic to breed in the summer. And that’s, what a 12,500 mile migration? That’s huge.
They’re quite big birds. And if you look at a rufous hummingbird, that’s tiny. I mean they weigh approximately the same as a British penny, around about 3 grams, which is next to nothing. So migration for bird that tiny of that distance, it’s just spectacular.
IRA FLATOW: And how long would that take? I would imagine, I’m asking, that for a 3,500 mile journey the bird is spending a lot of time searching and eating food. I mean to make that kind of journey and weigh next to nothing.
JOHN DONNE: Absolutely. They time their journey to be just at the cusp of the spring rolling North through America. They’re right on the cusp of that. It’ll take them some time. That bird, it was several months between it being banded in Tallahassee and being recovered up in Alaska. And so they resort to larceny. They find the wells drilled in trees by sap suckers, and when the sapsucker is not looking they dive in and have a little sip of the tree sap That’s where they get the sugar hit.
IRA FLATOW: No kidding.
JOHN DONNE: Yeah they’re little thieves.
IRA FLATOW: What surprises most people is that you could actually find hummingbirds, as you mentioned, close to the Arctic and Antarctic circles. What is, then, the coldest temperature a hummingbird can survive in? Because I’m always wondering what time of the year should I put my feeder out. Is it too cold for them?
JOHN DONNE: Well if you look at the hummingbirds which are found in the Andes, the ones which are really high altitude, up what 3,800 meters, it was a fabulous study done a couple of years ago where scientists were looking at six montane, high montane hummingbird species. And they found one particular species, the black metal tail, was existing at temperatures which overnight were dropping to just above freezing, 2.4 degrees Celsius. And to do that, those hummingbirds were entering a state of torpor at night. And they were actually dropping their body temperature from a daytime internal temperature of around 40 degrees Celsius down to 3.3 degrees Celsius. So just above the ambient air temperature. And that’s staggering.
I mean I’ve heard someone describe that as controlled hypothermia, which I think is a really cool way of describing that. And they slow the heart rate as well, at the same time. So they’re dropping from a sort of a daytime active heart rate of around 1,000 to 1200 heart beats per minute down to 100.
IRA FLATOW: Wow, wow. Does that make them sort of unique among all birds then, to have that talent?
JOHN DONNE: Pretty much. I think I read somewhere that whippoorwills can sustain very low temperatures, but I mean, I think the hummingbirds really have got that trick down pat. Again, this is something which wasn’t in the book, I was reading this only the other day, apparently NASA were looking at and their ability to enter torpor quite seriously thinking, would it be possible to put astronauts into a state of torpor for the long distance space travel. So these are the really inspiring birds.
IRA FLATOW: What is the definition of a hummingbird? To make it different than all the other birds, what kinds of things must it do?
JOHN DONNE: OK well the really obvious one is they hover. But actually, that hovering flight defines the very being of a hummingbird. They’re physiologically distinct to enable that hovering flight. So there’s a host of adaptations. They’ve got their pectoral, their breast muscles, the muscles which power their wings, make up about a third of their body weight. In most other birds it’s around 15%. So there’s almost twice as much muscle mass driving those wings. And those wings are connected to their sternum, to their breastbone in an almost unique way.
Only hummingbirds and their kind of distant relatives the swifts have a little tiny ball and socket joint which connects the wings to the body and what that lets them do is move their wings in a completely different way to normal birds, which, to make this really sort of basic, they flap up and down, yeah? But hummingbirds, they actually rotate their wings in flight, in approximately a figure of eight motion. And what this does is, it means that they’re getting them lift not just on the downbeat of the wing but also on the upbeat. So they’re getting about 75% of their lift from the conventional downbeat. But on the upbeat they’re still getting about 25% lift which is really efficient.
But of course, what they’re having to do to power all of this, and I’ve mention the heartbeat which is the motor of the hummingbird which is beating it it’s about 1200 beats per minute, it takes an awful lot of energy. And so hence they’ve evolved to use nectar as their fuel. It’s like a high octane fuel for hummingbirds.
IRA FLATOW: And speaking of nectar let’s talk about that special forked tongue and how it’s specially built to capture nectar.
JOHN DONNE: Oh I love this. Yeah I mean, if you look at some photos of hummingbirds– and in the past people obviously were examining hummingbird specimens– their tongues appear to have little tubes in them. And for years, people postulated that this must mean that they were feeding by some sort of capillary action. But I mean that doesn’t really make sense. You know nectar, as you were saying about your feeders in your yard with the syrupy sort of in the nectar substitute you put in them, that is pretty thick, gloopy stuff. And for the amount of time a hummingbird tongue is in a flower, capillary action couldn’t work.
And this is so cool. Someone got a hummingbird feeder and some high speed cameras, so we had effectively a transparent flower which they had cameras trained on. And the hummingbirds came and stuck their tongues into the feeder. And what they saw was amazing. The tongues actually blossom when they’re immersed in the nectar.
So the tongues unfold and they’ve actually got tiny little flaps which also unfold from the edges of the tongues. And when they pull the tongue back into their bill, all of the flaps and the folds close and trap nectar within them. Into the hummingbird it goes, and the very act of retracting the tongue into the hummingbird draws the nectar in as its tongue is flicked back out again, all the nectar is released back into the hummingbird. So it’s an entirely passive feeding technique. All they’ve got to do is dip their tongue in and out and nectar is drawn into them.
IRA FLATOW: In writing this book and taking the photographs of hummingbirds, you went after 300 species. Did you get all 300?
JOHN DONNE: Yeah, I blushed a little when you introduced me like that. I didn’t, know no I didn’t. Actually, I didn’t set out to see all 300 species. I wanted to see as many as I could. I’m not a lister. I’m not that kind of birder who is all about ticking off lots of species on the list. But at the same time, you know, I love the natural world and obviously I want to see as many wonderful things as I possibly can. Gosh, I’ve never actually counted up. There must have been a couple of species I’ve seen. But, kind of, that’s one of the pleasures of having things to still go and see. =-p
IRA FLATOW: Talking with John Donne natural history writer and photographer, author of The Glitter in the Green, In Search of Hummingbirds. On Science Friday from WNYC Studios. How much were you aware of the endangered or threatened situation of hummingbirds before embarking on this journey to document them?
JOHN DONNE: Because so many hummingbirds have very localized ranges and are found in one particular area of the Andes or, we were talking earlier about the one that’s found on an island just out in the Pacific and nowhere else. In some of those birds have really tiny populations, they’ve been reasonably well monitored and, yeah I knew that they were classified as Red Listed by Bird Life International. So I knew some of them were down to a few hundred individuals left in the wild. But I suppose what was more shocking was to discover that some of the ones which we would take for granted, like going back to that rufous hummingbird, the long distance migrant, and that’s a pretty common hummingbird in North America, and yet their population is in colossal catastrophically fast decline. It’s dropped by an order of 62% between 1966 and 2014.
IRA FLATOW: Wow, that is a drop.
JOHN DONNE: It’s huge, isn’t it? And I suppose in a sense they’re the most colorful canary in the coal mine because actually that’s just emblematic of a decline of biodiversity of all kinds. There was a really big study in the US looking at your [INAUDIBLE] fauna as a whole. And since 1917– this statistic shocked me. And once I’d heard about the hummingbirds, I was leaning deeper into this. Your bird life has actually dropped by a third, 29% to be specific, which is a net loss of three billion birds since 1970. And that’s really shocking. And actually you’ve got it better than we have here in Britain.
In the same period, Royal Society for the Protection of Birds did a study and actually found that our farmland birds have dropped 48%. So we’re not proving to be terribly great custodians of biodiversity. And, you know, we kind of know that. But to see hard black and white figures, flesh on the bones, that’s really chastening.
IRA FLATOW: I thought there was some really interesting things I never knew about hummingbirds. There’s so much to know. For example, people who keep hummingbirds as pets. They sort of take care of them. Some people specialize in caring for injured hummingbirds.
JOHN DONNE: They seem to bring out an emotional connection in people, which perhaps, other birds don’t. And I find that really interesting. And I wonder if it’s because they are– a lot of them anyway– are pretty tame. You know, they approach us really closely. I mean they’re a wild animal. They’re not really tame. But they’re very tolerant of us, aren’t they? And they’ll come to the feeders, right outside our window.
When I was in Cuba I had that big lens, the big telephoto lens on my camera. And I was looking for bee hummingbirds. And there was this great little male bee hummingbird, the smallest bird in the world, I was trying to track him in flight. And he was zipping around, he was really fast. And then you can hear of course, you can hear the flight. They really do buzz when their wings are beating so quickly. And suddenly that buzzing got really loud. I couldn’t focus on him.
And I realized he’d actually come inside the hood that shades the lens. He was right inside the hood and he was hovering inside there. And it was his own reflection which had brought him in. He’d seen another hummingbird. And he was there for a few seconds and then he sort of chattered angrily and shot off again because he had met I guess a rival who wouldn’t back down and fly away from his challenge.
IRA FLATOW: You must be very disappointed that you can’t put a feeder in your own yard and get a hummingbird there.
JOHN DONNE: Absolutely gutted, but a reason I moved to Shetland, oh gosh, some 20 years ago now, was because it’s a really great place to see bird migration in action. Every spring and autumn and we get vagrant birds balloon in here from all four corners of the world. We get Siberian birds which should be heading to Southeast Asia for the winter, they turn up here.
And we get American birds too. They get blown across the Atlantic and they turn up here in Shetland. So it’s a really famous place to see birds.
IRA FLATOW: Wow, so it’s a fair trade off, I would say.
JOHN DONNE: Oh, it’s a fair trade off. I mean, don’t get me wrong. If a ruby-throated Hummingbird turned up in my yard, but it’s not likely to happen.
IRA FLATOW: Thank you John.
JOHN DONNE: My absolute pleasure Ira.
IRA FLATOW: Fascinating stories. John Donne, natural history writer, photographer, and author of the book The Glitter in the Green, In Search of Hummingbirds.