Evolving, Swiftly

Photograph | Lee Rentz

THE FIRST RAIN IN WEEKS slickened I-5 as Thea and I drove south to see one of the great spectacles of northwestern natural history: the Chapman School swifts. Every September, as they stage for their migration to Central America, Vaux’s swifts congregate in the heating-plant smokestack at this Northwest Portland elementary school. When the importance of the avian bivouac was first recognized and publicized by Portland Audubon, the students, staff, and administrators of the school elected to wear sweaters and leave their furnace off until the swifts departed, saving thousands of birds’ lives. The heating system was replaced, but the stack left intact for the benefit of the birds and the many citizens who flock to admire them. Each evening during the staging period, folks gather on lawns around the chimney, much as the people of Austin assemble beneath the Congress Street Bridge to picnic and cheer the fly-out of a million Mexican free-tailed bats that roost there. As in Austin, a festival atmosphere reigns at Chapman, one barely dampened by the long-awaited rain on the evening we took part.

The showers also failed to discourage the swifts, or the insects on which they feed. We saw some six thousand birds working the airspace above the school (at the peak of the phenomenon, as many as thirty thousand birds dazzle appreciative watchers). Their dark gyre spread and spun over the neighborhood, then drew in toward the haven as light dimmed and, one by one, the birds disappeared into the stack. A Cooper’s hawk alighted on the rim, causing the airborne swifts to shriek and spread out. Then the hawk dropped into the black hole, snatched a sacrifice, flew off to eat it, and the swifts resumed their circling queue for fly-in. When the hawk came back for seconds, the swifts scattered once more. At last the raptor left, and the remaining swifts spiraled down inside that lightless pipe, like a plume of smoke running in reverse, swirling back into its stack. As the final bird fluttered, stalled, and then just dropped into the black, I thought helplessly of Tom Swift.

Tom, hero of a series of juvenile adventure books launched in 1910 by Edward L. Stratemeyer, is known for his clever inventions, his zip, and his pseudonymous author Victor Appleton’s love of tortured adverbs. A classic construction in a Tom Swift story might read: “‘I’ve found the missing jewels,’ Tom exclaimed brilliantly” or “‘It actually flies!’ he loftily announced.” Such locutions came to be known as “Tom Swifties,” and considered a field mark of overwriting beginners. It was partly in reaction to these easily parodied modifiers that many editors and writing instructors adopted the conviction that, without a darned good reason for being, most adverbs must die. How could I not think of Tom Swifties, as I beheld those thousands of birds falling spectacularly, darkly, swirlingly into a hole in the night?

Swifts, with their easy flutter, instant takeoff and turn, rise and fall, flick and weave, romance the air like no other fliers — not swallows, not falcons, not bats. People often conflate swallows, passerine birds of the family Hirundinidae, with swifts, the Apodidae, which are more closely related to hummingbirds than to sparrows and swallows. Through parallel evolution, both groups have acquired pellet bodies and cutlass wings. Swifts, however, are longer and slimmer of body and wing, even more adept in flight, and — in a word — swifter still. Swallows can function on the ground, landing and launching to gather mud and pebbles. Swifts, with their nearly vestigial feet (apodidae means “without legs”) cannot walk, only cling. So they spend most of their time on the wing — feeding, migrating, even mating aloft. I doubted the latter claim until one day at Joshua Tree National Park I witnessed a pair of white-throated swifts erupt from a boulder cleft in tandem, the male mounting the female in midair.

I have also watched white-throated swifts carrying bits of cellophane on high above granite domes in the Sierra Nevada, dropping them, catching, rising, dropping, again and again, in sheer play. I’ve gazed up at squadrons of sickle-winged black swifts migrating over high passes in the Cascades. And I’ve taken great pleasure in packs of the bird known in England simply as the swift (Apus apus, the sole species there), as they scream past tolling bell towers and over fish ‘n’ chip shops at dusk.

Swifts are largely urban birds in Europe, as is the chimney swift (Chaetura pelagica) in eastern North America. This preference for settled sites stems from a remarkable adaptive shift in these species’ habitat requirements. Swifts, sky-bound sifters of the aerial plankton, rely on cavities for roosting, nesting, and chick-rearing. Inside, they cling to walls with their claws, braced by their spiny tails, and affix bracketlike nests to vertical surfaces with sticky mucous. When most of the big old hollow trees vanished during the Middle Ages in Europe and later but more rapidly in colonial America, the swifts should have diminished, or even dropped out — yet they remain abundant today. Like metropolitan peregrines nesting on steel I-beams and feeding on feral rock pigeons, Old and New World swifts found a substitute for their vanishing support: chimneys and smokestacks. The European swift was also called “devil bird” for its sooty, stygian dwellings, and soon after the eastern American species was described, it acquired the common name “chimney swift.”

Vaux’s swift (Chaetura vauxi), a western species, abounded around tall dead trees when pioneer ornithologist J. K. Townsend described it in 1839. Both tree boles and broken branches, reamed out by rot, harbor the swifts. But as old-growth forests have shrunk around the West, capacious hollow trees have grown scarce. A western red cedar candelabra might last for centuries, but another species favored by swifts, black cottonwood, decays much faster — creating habitat quickly, but ephemerally. It is the entire mosaic of growing, dying, decaying, and regenerating trees that has served the swifts so well in the West, and it is just that mix that has been compromised by industrial forestry and an associated increase in the size and intensity of forest fires. As a result, Vaux’s swift has turned up on several state lists of species of concern in recent years.

Yet this bird too has been showing signs of an adaptive future. The first site purchased with Washington’s personalized license plate habitat fund, in the late 1970s, was an old square smokestack at an abandoned mill on the Klickitat River where migrating swifts roost each fall. Evidence is also beginning to accrue of Vaux’s swifts actually nesting in chimneys. In 1944 Rachel Carson observed that “the western cousin of the chimney swift — Vaux’s swift — only of recent years has begun to make the transition from trees to chimneys.” Reported cases of chimney nesting were still uncommon half a century later when, on a rainy, fireplace kind of day in May, our neighbors heard swift chicks peeping in their chimney.

I would rather have our swifts move into town than pass from the scene altogether, but I’d far prefer to see them remain country birds that only occasionally visit cities. For as delightful as city swifts may be in Vienna, or St. Louis, or either Cambridge, they represent the failure of human cultures to maintain complex woodlands. Out here in Vaux’s country, we could end up with an agreeable mix of swift habitats — but only if we adopt a silviculture that maintains fully functioning, recycling forests, as well as preserve chimneys and silos where healthy forests are lacking.

No doubt, it is exciting to witness adaptation in other species firsthand, but there is a dimension of this story that applies to humans as well, for we are losing vital elements of our own habitat — soil, water, and space, for starters. Will we too get a second chance? As I watched that dusky vortex settle into the Chapman School chimney, it occurred to me that we’d better start doing some evolving of our own — and swiftly.

Robert Michael Pyle is a lepidopterist and a professional writer who has published twelve books and hundreds of papers, essays, stories and poems. His acclaimed 1987 book Wintergreen describing the devastation caused by unrestrained logging in Washington’s Willapa Hills near his adopted home was the winner of the 1987 John Burroughs Medal for Distinguished Nature Writing. His recent books include Where Bigfoot Walks: Crossing the Dark Divide, Wintergreen: Rambles in a Ravaged Land, and Sky Time in Gray’s River: Living for Keeps in a Forgotten Place. He won the 2007 National Outdoor Book Award. In 2011, he won the Washington State Book Award in the biography/memoir category for his most recent work The Mariposa Road: The First Butterfly Big Year.