Pollination by Hummingbirds

Hummingbirds are a strictly New World group of birds, some 375 species (family Trochilidae) found from Alaska to southern Chile and Argentina. They are the main group of birds that pollinate in the New World. Fast and often brightly colored, people love to watch them. They typically hover while probing flowers for nectar, a fascinating sight. 

hummingbird pollinating Monarda

Hummingbirds have co-evolved with plants to be impressive pollinators. I almost always look at it from the plant's point of view, so here is a bit about hummingbirds as pollinators.

 Pollination moves pollen, containing sperm, from the plant where it was produced to the stigma of (the same or) another flower, where it grows down into the ovary to fertilize an egg, producing seeds. Key to good pollination for plants is that the pollinator, having gotten pollen on itself, goes to another flower of the same species in a reasonable amount of time, visits different plants, doesn't leave the pollen on some other species of plant, and doesn't damage the ovary in the process. For this service, the plant offers the hummingbirds nectar (sugar water) rich enough to fuel the energy hummingbirds need to fly and to hover. 

Hummingbirds are some of the best pollinators because they do visit many flowers of a species they like and will fly long distances for additional flowers. In return, the plants have to offer plenty of sugar-rich nectar. It is a complex trade-off: enough good nectar that the pollinator gets enough energy to keep it flying, not enough that the pollinator finishes the visit full and finds a perch to take a nap. The energy needed for a hummingbird to fly is more than for smaller insect pollinators and consequently requires more nectar production from the plant. The plant therefore benefits if all the nectar goes to hummingbirds and is not shared with bees or flies. This has led to plants that have flowers specialized for hummingbirds as their pollinators. Generally these are narrow tubular flowers sticking out into space. That is a good shape for a hummingbird to probe with is beak while hovering. The tube is too narrow for most bees or flies to climb into and provides no place to land to feed, so beetles and most butterflies are excluded. Hummingbirds get nectar; plants are pollinated.

scarlet gilia, Ipomopsis aggregata 
a classical hummingbird-attracting flower 

Hummingbirds see about the same colors as humans, and like people, they are attracted to bright red flowers. They like other colors too. However many bees cannot see red--it is the same as black to them--so a true red flower signals "Nectar here!" to hummingbirds but not to bees. Butterflies like red, so other aspects of the flower are needed to exclude them. 

One or more species of hummingbird is found across all the Americas, with the possible exception of the middle of the plains of the Midwest and center of the pampas of South America. Far north into Canada and Alaska, far south toward Patagonia, hummingbirds arrive seasonally to feed and breed in the summer abundance at high latitudes. So all across the Americas there are flowers adapted to hummingbirds as their pollinators.

In the tropics, some hummingbirds are twice the size of the Ruby-Throated Hummingbird of the U.S. East or Anna's Hummingbird of the West Coast. They can visit quite large flowers, which make a startling display to attract them. The New World tropics has many different species of hummiingbirds, large and small, aggressive and shy, so while big flowers catch the eye, many flowers of different sizes, shapes and colors are pollinated by hummingbirds as well. 

These heliconias (Heliconia, heliconia family, Heliconiaceae) make a bright red splash to attract pollinators. The actual flowers are small and yellow, but the big red bracts get attention and position the nectar-filled tubular yellow flowers where hummingbirds conveniently investigate them, and consequently hummingbirds pollinate many heliconias. 

flowering heliconias (Heliconia)
a mainly American group of plants

This is a cultivated hibiscus (Hibiscus, mallow family Malvaceae). You can see that pollen (yellow) and stigma (red organs even farther out from the flower than the pollen) stick way out, so will brush the hummingbird's back or sides as it sticks its bill into the openings at the center of the flower, probing for nectar. (Oops, nothing there for scale: its about 3" across)

red Hibiscus

This is another member of the mallow family, turk's cap, Malvaviscus, seen growing wild in Costa Rica. It has a one inch flower, but is bright red and well-shaped for hummingbird visitors.  

turk's cap, Malvaviscus

Generally as you move into the temperate zones, flowers are smaller because the growing season is six months or nine months, but not all year long. Still, there are hummingbird-adapted flowers well outside the tropics. 

Trumpet creeper, Campsis radicans (catalpa family Bignoniaceae), native to the U.S., is a classic example of a hummingbird-pollinated vine. Its big red flowers stick high into the air, inviting hummingbirds.  

 

trumpet creeper, Campsis radicans 

(Bees also sometimes pollinate trumpet creeper. Only very rarely do plants have only one pollinating species. A mix of pollinators ensures pollination even when something happens to the main pollinator. The excellent quality of hummingbird pollination and the amount of nectar they require has led to relative specialization so that we can say "hummingbird flower" for a particular shape and color of flower, but even plants specialized for hummingbirds are sometimes pollinated by some other organism.)

Red-flowered columines, Aquilegia canadensis of the eastern U.S. and Aquilegia elegantula the western red columbine, are also specialized to attract hummingbirds. The long spurs at the top contain rich nectar. The nodding shape of the flower allows an agile hummingbird to fly up from underneath, hover, put its bill into the flower and up into the spurs, and let the nectar run into its tongue. Bees land on the flower and their weight bends down; sometimes they get nectar and transfer pollen despite the awkward position. Butterflies land on the flared petals and bend around to get nectar. 

 

 eastern red columbine, Aquilegia canadensis

In the United States, the greatest number of hummingbird species are in the dry southwest, Texas and Arizona especially. Many desert plants attract hummingbirds, producing dramatic narrow red flowers from a nondescript cluster of leaves. Below you see the striking hummingbird flowers from this Tillandsia (a genus of the bromeliad family, Bromeliaceae). It is an "air plant" that growing on other plants, found from the deserts and mountains from Mexico southward, normally high in trees, but seen here in a conservatory in Seattle. 

Tillandsia flowers

The tubular flowers help keep out nectar thieves and protect the nectar from rainwater. Some plants have specialized so much that their flowers curve to match the curve of the beak of the two or three species of hummingbird that visit their flowers.

Hummingbirds pretty much require forests, so although they can be found all over the continent, the plains and prairies are only visited by them as they migrate. Notice the color array in American grasslands: there are few red flowers. 

Hummingbirds are not limited to visiting red flowers. They are smart animals and will probe flowers of any color and any shape they can reach into, looking for nectar. If they find it, they'll try other flowers on that plant. Consequently lots of very different flowers feed hummingbirds, it is just that red tubular, nectar-rich flowers represent plants responding to hummingbirds as good pollinators with flowers that are very attractive to hummingbirds. 

As a preteen in upstate New York, I had a favorite bent weeping willow where I climbed to read on summer afternoons. Below it was a marshy area full of jewelweed (Impatiens capensis). Their flowers were about the size of a thimble and yellow-orange, not red. One of the treats of that spot was watchng  Ruby-Throated Hummingbirds visit the jewelweed flowers. If you watch hummingbirds, you will see them visit flowers of all colors and a wide variety of shapes.

spotted jewelweed, Impatiens capensis

I have few photos of hummingbirds, and most of them are from feeders. Here is a Broad-tailed Hummingbird I was able to photograph in Estes Park, Colorado. 

Broad-tailed Hummingbird, Colorado

Hummingbirds are an American bird family, not found across the Old World. Bird pollination happens at least on a small scale everywhere, but hummingbirds are flashy. They are one of the highlights of my summer days and must be even more exciting to visitors from outside the Americas. And, as a consequence of hummingbird abundance, the Americas are rich in native plants with bright red flowers. This is a noticeable difference if you look at flower colors in natural areas, with no or few hummingbirds, in the Alps or mid-American prairies, for example. The flowers are lovely yellows, purples, and blues; you don't notice the missing reds unless you look for them. Pollinator preferences shape our plant communities.

Comments and corrections welcome.

Note: hummingbird feeders enhance our ability to see hummingbirds, in fact they are pretty much the only places I can successfully photograph hummingbirds. And yet, providing lots of sugar-water makes it easy for the birds to hang around the feeders and not fly through the forests pollinating, consuming small insects and otherwise "doing their jobs." A valid counterargument is that providing extra food is a good thing since we have replaced forests with homes and parking lots. Somewhere there is a middle ground. One step toward the middle is to plant lots of hummingbird-attractive plants, from columbines to trumpet creeper to red salvias... (And they don't require that you refill them frequently or fight off ants).

Note 2: Every state in the U.S. has hummingbirds except Hawaii. Hummingbirds forage in the prairies at the edge of the forests, and follow river valleys into the midwestern grasslands. Some are expanding their range as people plant trees and hummingbird flowers in what were grasslands. You will find all kinds of exceptions to my general statements in this blog: enjoy the fact that neither hummingbirds and hummingbird flowers are bound by the generalizations biologists make. 

References

Proctor, M., P. Yeo and A. Lack. 1996. The Natural History of Pollination. The Timber Press, Inc. Portland, OR. 

Van Nest, B. V., A.E. Edge, M. V. Feathers, A. C. Worley, and D. Moore. 2020. Bees provide pollination service to Campsis radicans (Bignoniaceae), a primarily ornithophilous trumpet flowering vine. Ecological Entomology. https://doi.org/10.1111/een.12947 open access. (Accessed 1/4/26)

The internet, where I checked the spelling of plant names and looked up plant families (faster than looking them up in a bood)

Comments and corrections welcome.

Kathy Keeler, A Wandering Botanist
More at awanderingbotanist.com
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