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Public Radio's Environmental News Magazine (follow us on Google News)

Missed Connection in the Rockies

Air Date: Week of
A male Broad-tailed Hummingbird (Selasphorus platycercus) at the Rocky Mountain Biological Laboratory. (Photo: David W. Inouye)

In Colorado’s Rocky Mountains, Glacier lilies and Broad-tailed hummingbirds have a long-standing spring tryst. David Inouye, professor of biology at University of Maryland and the Rocky Mountain Laboratory, tells host Steve Curwood that the changing climate is causing a missed connection.


CURWOOD: Well, as Mark Seth Lender says, timing is everything. And that’s vitally important when spring comes to the Rocky Mountains as well. So says a new study in the current issue of the journal Ecology. David Inouye, Professor of Biology at the University of Maryland and the Rocky Mountain Biological Laboratory in Colorado, joins us from the Rockies to tell us about missed connections.

Welcome Professor Inouye!

INOUYE: Hello! Glad to be with you.

CURWOOD: This is a tale of two species: a hummingbird and a flower. Could you describe them for us please, Professor?

INOUYE: The glacier lily is the second flower to come into bloom after the snow melts, hence I think the common name. It’s a yellow lily, the flowers are maybe about a foot off the ground, and a young plant will just have one flower, an old plant might have as many as nine of these beautiful yellow lily flowers.

A female Broad-tailed Hummingbird visiting flowers of tall larkspur (Delphinium barbeyi), another important nectar source for hummingbirds. (Photo: David W. Inouye)

The broad-tailed hummingbird is a very small bird, very easily fits inside the palm of your hand and only weighs about three grams or not much more than the weight of a penny. And yet these birds are long distance migrants. They’ve flown up here from Central America, from the mountains in Mexico or Guatemala to breed here in the Rocky Mountains.

CURWOOD: And if I were to look at the bird, how would I identify it from different hummingbirds?

INOUYE: Well, you can actually identify the male broadtail with your eyes closed, because you can hear the wing whistle that the male makes with his aerodynamic slot between the first two feathers of each wing. If you open your eyes and look at the bird, the males have a beautiful, ruby, iridescent gorget—the feathers at the base of the head, around its throat are an iridescent ruby color.

The females are not so brightly colored, but they’re both beautiful birds to watch at a feeder or to watch at these flowers.

CURWOOD: So you’ve done some research about the broad-tailed hummingbird and the glacier lily. How are they usually connected to each other?

INOUYE: Well, the broad-tailed hummingbirds are migrants, and when they arrive here, one of the first flowers to bloom after the snow melts and the first flower which they will visit for nectar, is this beautiful yellow flowered glacier lily.

A male Broad-tailed Hummingbird at the Rocky Mountain Biological Laboratory. (Photo: David W. Inouye)

CURWOOD: Now, Professor Inouye, how did you set up this study?

INOUYE: Well, it’s sort of coincidental that I was studying the flowers. I set that project up as a graduate student here at the Rocky Mountain Biological Lab in 1973, and we’ve kept that study going for about a hundred different species of wild flowers ever since then.

And then another co-author of this study, Billy Barr, has lived up here year-round at the Rocky Mountain Biological Lab since about 1974, and he happened to keep track, I just found out about ten years ago, of events like when he heard the first hummingbird in the springtime. So we had this coincidental record, the two partners: his data for the hummingbirds and mine for the wildflowers. And we decided last year that we’d try and look at those data and see what sort of story we could put together.

CURWOOD: What’s changed about the relationship?

INOUYE: Just about anywhere where people have looked at the timing of seasonal events, including migration by birds and flowering by wildflowers, those events are happening earlier in response to the change in climate.

So the link here is that the hummingbirds are arriving earlier than they used to. They’re now arriving about five or six days earlier than they did back in the 1970s. But the flowers are blooming even earlier. They’re now blooming about 17 days earlier than they did in 1975.

And so our concern here is that there’s a developing mismatch between the timing of these events that used to be synchronized; that eventually there may be problems both for the flowers, because the pollinators aren’t arriving in time, and for the hummingbirds, because they’re losing out on the beginning of the availability of nectar.

A glacier lily (Erythronium grandiflorum) flower. Glacier lilies flower within days of snowmelt, and are an important nectar resource for newly-arrived migratory Broad-tailed Hummingbirds. (Photo: David W. Inouye)

CURWOOD: How possible is it for these species to move even higher up the mountain, to a colder place with the changing climate?

INOUYE: That’s an interesting question. There are good data that show that a number of plants and animals have already started to migrate either north in latitude or up in altitude.

So for instance here at the Rocky Mountain Biological Lab, we now have foxes that spend year round up here which we never used to have; we have crows nesting up here which we never used to have; there’s a new species of mosquito that’s appeared up here; we’re occasionally starting to see ticks; and there’s also a species of bumblebee that used to be pretty rare at this altitude which is now very common at this altitude.

So there’s a good chance that those plants and animals may be able to move up in altitude. The question that that then raises is what happens to the plants and animals that were already at those higher altitudes?

CURWOOD: Why should people care about missed connections between species? I mean, what do we as people stand to lose if climate change unravels these relationships?

INOUYE: Well if you care about plants and pollinators, which are important both aesthetically and economically, I think there’s reason for concern. About one out of every three bites of food that you eat comes courtesy of the activity of pollinators.

And although we’re beginning to get an understanding here at this one study site of how that relationship between plants and pollinators is being affected by climate change, in general, we don’t have a very good understanding of that and it’s something for which we need a lot more research at this point.

CURWOOD: I want to play you the sound of a broad-tailed hummingbird.


CURWOOD: What’s going on here?

INOUYE: Well, you’re hearing two different sounds. One is the sound that’s made by the wings of the male broad-tailed hummingbird and when they flap their wings they make a whistle. And the other noise that you’re hearing is the chirping, the vocalization that could be made by both males and females, and so it’s those two sounds superimposed.

The Rocky Mountain Biological Laboratory, Gothic, Colorado. (Photo: David W. Inouye)

Part of the sound that you were hearing was the male broad-tailed courting a female, and actually I’m looking outside my window right now and I see one of those males courting a female. So he’s flying little arcs back and forth about a foot over the head of the female. And then he’s going to fly up maybe about thirty feet over the female and then do a power dive down towards her and then back up again in a U-shaped dive, and that’s part of the mating behavior that they’re going through this time of year.


CURWOOD: Now of course hummingbirds like sugar—does this guy have chocolates, wine, what does he have for her?

INOUYE: [LAUGHS] Well he’s hanging out here next to a feeder on my cabin, and defending that feeder against other males. And that’s typically what they would do if they found a rich patch of flowers. They defend that patch of flowers and hope females would come by, for which they could display.

CURWOOD: David Inouye is Professor of Biology at University of Maryland and at the Rocky Mountain Biological Laboratory. Thank you so much for taking this time.

INOUYE: You’re quite welcome.



Professor David Inouye’s faculty profile for the University of Maryland.


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