Red-eyed Vireo Nests: Hidden Treasures of See-Through Season

Cold air filled my lungs as I climbed yet another flight of stairs up to the observation tower at Copper Falls State Park. It was interesting looking out through the twigs and trunks. The lack of leaves in this “see-through season” reveals aspects of the landscape otherwise obscured. For example, “Check out that nest!” I exclaimed to my friend, and we admired the small cup suspended between a Y in the sugar maple twigs. It was a lovely reminder of a favorite summer resident, now gone for the winter.

Can you see through the forest and spot the vireo nest? It's fun to get to look down on one! Photo by Emily Stone.

The placement of the nest dangling below the forked twigs, plus the few pale strips of paper from a bald-faced hornet nest woven among grass, bark, and pine needles, told me that it was likely built by a red-eyed vireo. While red-eyed vireos are one of the most common birds of eastern and central North America, these small, olive-green songbirds are hard to see among the leaves in the dense forests they prefer. Once the leaves fall, though, their nests are suddenly one of the most visible and recognizable of any songbird.

It's the female vireo who builds the nest in spring. She usually chooses a deciduous tree or shrub and places the nest 10-15 feet above the ground, and far enough out from the trunk so that it doesn’t block their view. Suspending a nest near the tips of thin branches reduces access for heavy nest predators like squirrels. On the chosen branch, the vireo weaves together fibrous strips of the inner bark of trees and other plant fibers to suspend the nest between the twigs. Pine needles often line the 2-inch-diameter inner cup. Spider webs help stick it all together.

As mentioned above, vireos often decorate the outside of their masterpiece with paper strips stolen from last season’s abandoned bald-faced hornet nests, even when those nests are not found nearby. Naturalists suspect that décor can trick potential predators into thinking it’s the nest of a furious stinger instead of a tasty songbird. Strips of birch bark often add to the papery look.

Almost every bird nest is a work of art. They are also feats of engineering that gently cup fragile eggs and chicks while withstanding storms, and then remain intact long past their intended use. Plus, they were constructed without opposable thumbs!

There’s a display at the Cable Natural History Museum that reinforces my awe. A Museum naturalist, decades ago, deconstructed a red-eyed vireo nest and catalogued each component. The nest included: 1 cherry stem, 1 piece of paper, 1 ball of tree sap, 2 pieces of thread, 7 fir needles, 9 plant buds, 69 pine needle sheaths, 16 pieces of hornet nest, 24 twigs, 50 animal hairs, 346 pieces of birch bark, 347 pine needles, 427 pieces of inner bark, and 16 pieces of spider web. The naturalist arranged these objects, minus the spider webs, in a beautiful display that hangs in our classroom.

This deconstructed vireo nest is a favorite display at the Cable Natural History Museum. The number of different nest materials is astounding! Photo by Emily Stone.

Despite the birds’ hard work, and the hornet paper, red-eyed vireo nests are vulnerable to nest parasitism by brown-headed cowbirds. When vireos can place their nests in the heart of a forest this is less common, but any vireo nest near a forest edge may end up with a cowbird egg among the 3-4 vireo eggs. The cowbird hatches first, grows faster and bigger, and will often push their adopted siblings out of the nest. Occasionally vireos will cover up the cowbird eggs and try again, but more often the parents just feed the big baby as one of their own. Vireos may nest multiple times per summer, especially if early nests fail.

Recently I noticed two vireo nests in the tops of trees surrounding my own driveway. Although the nests are much higher than average for a red-eyed vireo, that was the only vireo species I heard singing last summer. Warbling vireos are known to nest up high, but I would have recognized their run-on song, which sounds like them saying, as if to a caterpillar, “when I see you, I will squeeze you, and I’ll squeeze you ‘til you squirt!” Instead, I heard red-eyed vireos singing the incessant phrases “hear I am, over here, in a tree, look at me, vireo!”

All summer, it’s much easier to hear red-eyed vireos singing than to actually see one high in the treetops. This signing male was a lucky find! Photo by Emily Stone.

As their abandoned nests fill with white snow instead of white eggs, the vireos themselves are filling up on fruit in the Amazon basin of South America. When they return next spring, the females will start building new nests. Once the leaves fall, we’ll have a whole new set of treasures to discover in “see-through season.”

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is open with our brand-new exhibit: “Anaamaagon: Under the Snow.” Our Winter Calendar is open for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.

Winter Songs of White-Throated Sparrows

During a recent week-long visit to the Washington D.C. area, finding pockets of nature with plenty of birds was a boon to our sanity. Early in the week, my partner and I drove west to the little town of Linden, Virginia, which provided the nearest access to the Appalachian Trail. Even as we crossed the gravel parking lot toward the oak-filled forest and uphill climb, a wistful-sounding white-throated sparrow sang from the brush. We looked at each other and grinned.

The rhythmic whistle of white-throated sparrows is part of the spring and summer soundtrack of the Northwoods. No hike or paddle is complete without their song. Two decades ago, while my parents helped me pack for a May trip to the Boundary Waters, this was the one song they’d insisted I learn to recognize. Luckily, it wasn’t hard. The white-throat’s pattern of two long starter notes followed by three sets of triplets is often described with the mnemonic “Oh, sweet Canada, Canada, Canada” and is quite distinctive.

But it’s been a month or more since we heard the last sparrow sing goodbye to the Northwoods as they headed south. I felt a little sheepish, realizing I’d never paid much attention to where they were going. Virginia, as it turns out, is in the core of their winter range. As we hiked, it seemed like almost every scritching sound in the underbrush turned out to be a foraging sparrow using their two-footed hops to unearth seeds in the duff. Getting a glimpse of snazzy black-and-white head stripes, yellow near the eyes, and the signature white throat patch confirmed their identity.

White-throated Sparrow. Photo by Larry Stone. 

Higher up in the trees, cardinals whistled, tufted titmice peter-peter-petered, Carolina wrens chattered energetically, and Carolina chickadees scolded each other. These are common winter compatriots of the white-throated sparrows.

A few days later, we crossed over a babbling brook on a wide wooden bridge and into the “R. Randolph Buckley ‘8-Acre’ Park” in Clifton, Virginia. Large beech trees, sycamores, oaks, maples, and pines, plus musclewood and a blooming witch hazel, welcomed us into this little neighborhood woodland. As we followed our ears to a white-breasted nuthatch high in a pine tree, a song burst out of a bush beside us. The white-throated sparrow riffed on the usual song, experimenting with a gravely “sweet can-a-NA-da can-a!” “Jazzy!” We laughed to each other. Listen here!

I don’t usually expect birds to sing in their winter habitat. Birds’ songs are typically used to attract mates and defend territories, and therefore are most useful in spring and summer. Many birds get by using simple call notes to communicate within a flock over the winter. So, we figured we were hearing young males practicing for the coming year. That would also explain why the amateurs’ “sub-songs” were tending shorter and with more variations in rhythm and tone. As it turns out, that was only part of the story.

Singing on their wintering grounds is more than just training for the youngsters. It’s an important avenue for learning new songs! In 1999, two ornithologists in western Canada heard white-throated sparrows singing a shorter song. Instead of the triplet “can-a-da,” they heard a doublet, “can-a.” Over the next few years, scientists studied older recordings of the white-throat’s songs, and made new observations, too. In ten years, by 2019, the new song had been adopted as far east as Ontario. Currently, you can only hear the original song in the farthest east populations.

How did the new song spread so quickly when these sparrows breed clear across Canada? They learned from each other on their wintering grounds and then took the new “slang” back home in spring. This goes against traditional wisdom, that young birds learn to sing from their fathers before they leave home. Song spread is facilitated because male sparrows from all over are extra concentrated. They tend to stick to the north end of their winter range—poised for a rapid return to claim a breeding territory in spring—while females go farther south to avoid competition with the males.

Just singing a new song isn’t enough to make birds successful, though. If it’s not recognizable to your own species, or sounds weird, a new song might hurt your breeding success. In this case, females prefer the novelty of the males’ new song, and this reinforces the change.

I’d heard about the white-throated sparrow’s changing songs before, but it wasn’t until I investigated the young birds’ jazzy riff that I realized it had taken over so completely. I’ve been trying to shoehorn their summer songs into the familiar “Oh, sweet Canada” mnemonic, and attributing variation to lazy birds. Now I know that something much more interesting is going on. Just like the sparrows, I learned something new in their winter habitat.

Emily’s award-winning second book, Natural Connections: Dreaming of an Elfin Skimmer, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.

For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. The Museum is open with our brand-new exhibit: “Anaamaagon: Under the Snow.” Our Winter Calendar is open for registration! Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.