For years, the shops along Chapel Hill’s main drag have hosted migrating Chimney Swifts. The birds gather in swirling flocks above Franklin Street at dusk, before entering chimneys to roost for the night. Until one day, they didn’t. 

One evening last fall, Barbara Driscoll was doing her usual swift surveys for an ongoing program by New Hope Bird Alliance, but the birds never came. A few circled a chimney, then flew off. She heard the twittering of a larger flock in the distance. Then a cloud of swifts rose above the trees.  

She followed the birds onto UNC Chapel Hill’s campus, to the base of the Davie Poplar, the school’s largest and grandest tree.  

“There were just thousands of them, it was pretty incredible,” said Driscoll, who is a New Hope Bird Alliance board member. As the sun set, the swifts tightened their orbit around the trunk until, one-by-one, they dropped into a large cavity for the evening.  

Driscoll made the initial discovery near the end of last year’s migration season and visited this August to find that the swifts had returned to the same tree. 

This behavior is normal for Chimney Swifts. The location is not. 

As their name suggests, Chimney Swifts nest and roost in chimneys, as they have since European settlers cleared old growth forests across the eastern U.S. centuries ago. Today, reported cases of swifts using trees are scarce. The Davie Poplar may be the first documented swift roost in a tree in North Carolina and beyond since that era. 

“The fact that this is happening in such a central, high-profile location is remarkable, and a great opportunity for folks to get a close-up look at this amazing bird,” said Curtis Smalling, Executive Director at Audubon North Carolina. “But it also underscores how much we’ve pushed Chimney Swifts to the limit.” 

Life on the Wing 

Chimney Swifts aren’t remarkable for their physical beauty. They are small and blackish with stiff wings; people often mistake them for bats. What makes them remarkable is how they live their life, spending nearly every waking moment on the wing.  

Swifts touch down only to nest and roost. Historically, they did this in large trees or caves, where their strong feet allow them to cling to vertical surfaces. Chimney Swifts are otherwise unable to perch, walk, or hop. 

When old growth forests were chopped down centuries ago, swifts went looking for the next best place and found the chimneys of growing human settlements.  

By the late 1800s, ornithologists openly considered the question, including Alexander Wilson. "Where did these birds construct their nests before the arrival of Europeans in this country?" he wrote in American Ornithology in 1812, before postulating the answer: “in the hollow of a tree.” 

All of this makes the present-day Davie Poplar roost “incredibly unique,” said John Connors, a long-time Wake Audubon board member who has studied Chimney Swifts in North Carolina and beyond. Over the years, Connors has collected second-hand observations of swifts using natural structures. But the reports are few and far between. 

“I did save a photograph someone posted of [a nest] found inside a cypress tree from South Carolina several years back,” Connors said. “There may be a good bit of that going on in forests with older trees—we just don't know.” 

One academic paper published in the 2000s found fewer than two dozen reported instances of tree-nesting in the last century.  

In New Brunswick, Canada, Allison Manthorne has worked with Birds Canada to protect Chimney Swifts for years and now leads the organization’s aerial insectivore work. “For centuries now, we haven’t had a lot of trees that would be big enough to host roosts,” Manthorne said of her home province. “We know of a few nest sites [in trees], but those would be in small cavities.”  

One report we do have of a large roost in a hollow tree was made by John James Audubon himself, in his book The Birds of America. Audubon claims to have witnessed a flock of 9,000 swifts nesting in a sycamore outside of Louisville. That was nearly 200 years ago. 

And yet, the Davie Poplar roost isn’t completely surprising. The tree is nearly 400 years old, with a large, partially hollow trunk—just the profile for a natural roosting site.  

Legend has it that the campus was planned around the tree, and great care has gone into propping it up. Its trunk is filled with cement, while cables hold up its larger limbs.  

The tree is a great example of the importance of maintaining natural features in urban areas and the unexpected ways it can benefit wildlife, said Doug Tozer, a swift researcher and director of waterbirds and wetlands at Birds Canada. “Where some might only see an unsightly dying tree, there is actually instead much, much more going on here, and much, much more value of such trees than initially meets the eye,” Tozer wrote in an email. 

Today, it’s likely that swifts continue to live in old growth trees, where they still exist. The Black River in eastern North Carolina is one likely place, where 2,000-year-old giant bald cypress still stand, hollowed out but alive. But the existence of remnant tracts of old growth hasn’t been enough to help this threatened species. 

Rapid Decline 

Despite their early adaptation to humans, Chimney Swifts are in trouble. Populations dropped by 50 percent in the last half century. In Canada, the declines are steeper—as much as 90 percent since the 1970s. 

Culprits include fewer suitable chimneys, which have been lost to capping and changes in construction style. As towns are redeveloped, older chimneys that are ideal for swifts—those made with rough-surfaced brick, stone, or masonry tiles—often aren’t replaced, and metal-lined chimneys are too slippery.  

But perhaps the biggest driver is the loss of insects, which swifts catch on the wing. One study that looked at decades of Chimney Swift droppings at the bottom of a single chimney found a marked change in their diet.  

The lower layers of excrement, which dated to the 1940s, showed more beetles and less of the pesticide DDT. But higher up in the column, DDT levels increased and the more protein-rich beetles were replaced by flies, leafhoppers, and other less nutritious bugs. The theory is that the beetles were more susceptible to DDT, and their population crash is still impacting swifts and other birds that relied on them for food. 

Manthorne,, of Birds Canada, also points to stronger and more frequent storms as a growing threat, particularly during migration. In October of 2005, Hurricane Wilma traveled up the eastern seaboard, dragging thousands of migrating swifts back north, when there few insects left to sustain them.  

“Thousands of birds ended up at rescue centers or found dead in chimneys,” Manthorne said. One study in Quebec found that the storm reduced the province’s swift population by 50 percent the following year. 

All of this adds up to a species in steep decline. In 2018, the International Union for Conservation of Nature changed the Chimney Swift’s status from near-threatened to vulnerable.  

Taking Action 

New Hope Bird Alliance is raising awareness about the threats faced by Chimney Swifts and other species that hunt insects on the wing, a group of birds known as aerial insectivores. Learn more about the chapter’s Year of the Aerial Insectivore here. 

You can witness the Davie Poplar swifts at watch parties hosted by New Hope Bird Alliance and the UNC Avian Society. (Find swift events elsewhere in the state here.) 

Davie Poplar Swift Roost Watch Events: