A Swift Passage

Fall brings the ritual of counting these migratory birds, as astounding numbers funnel into chimneys -- a rapidly vanishing sanctuary.

October 14, 2001|By Linell Smith | Linell Smith,Sun Staff

Alice and David Nelson hunkered down on a concrete divider in a parking lot in Hampden, binoculars trained on the brick chimney of the Mill Center office complex. It was a beautiful Saturday evening, the kind of precious, last-gasp-of- summer evening tailor-made for romance ... or at least a family picnic.

Instead, the Nelsons made ready to count birds.

They didn't have long to wait. A few dark specks started flying overhead, then more and more. In a matter of minutes, the sky above them filled with the black shapes of chimney swifts, hundreds of them, circling until the dusk seemed sprinkled with pepper flakes. The birds looped around the tall chimney of the 19th-century mill in a loose funnel shape, chittering away.

Then they started to enter it. Two, three, five, 10 low-flying birds would fold their wings and drop into the stack like crumpled pieces of Kleenex. There would be a break as the other birds continued their circling formation. On some mysterious signal, a succession of 10 or 20 or more birds slipped in, at times appearing like a plume of smoke in reverse. They were performing a timeless ritual, creating one of the communal roosts that sustains them during intercontinental travel.

Keeping her eyes trained only on the chimney top, Alice Nelson called out birds in units of 10 as they disappeared into the chimney, her husband making a pencil mark for each grouping. By the time the couple had finished counting, 4,478 birds had entered the Mill Center chimney for the night.

Check-in had taken no more than 40 minutes.

To look at the chimney now was to believe that you hadn't actually seen what you had actually just seen.

The wonder of this fall spectacle had kept the Nelsons, who work in visual display design and graphic arts, watching these migratory birds for more than 20 years. They had followed them to various chimneys around Baltimore, sometimes counting them for the Maryland Ornithological Society. Now the couple was part of a new effort: The first nationwide chimney swift roost monitoring project. Their report would also benefit a bird conservation program launched by the Center for Conservation of Biology in Williamsburg.

And the chimney at Mill Center would soon have an official identity: USMD001.

On the fly

To most people, the chimney swift is a particle of peripheral vision, a flicker-winged, chittering bird often mistaken for a bat.

Instead, these small, cigar-shaped birds spend their entire days in flight, only heading toward shelter at dusk. Once inside a chimney, each bird finds its own foothold and clings upright to the porous surface with specially designed claws and tails. When the birds are settled, they compose tight vertical rows, perhaps overlapping one another on the interior like feathered roof shingles. (Such close quarters, ornithologists believe, help keep the birds warm and also minimize the likelihood of droppings.)

At dawn, swifts leave their chimney for a full day of catching and devouring insects, their exclusive diet. They must eat a prodigious amount to support the calories they use in flight. The unusual claws which enable them to roost prevent them from balancing well or even perching. Instead, they eat, drink, gather nesting material and even mate on the fly.

Chimney swifts are migratory birds. As insectivores, they must fly farther south to find food as the weather turns colder. Their summer range extends north to Canada and west to Texas. This time of year, swifts head toward South America -- some wintering in Peru and others throughout the Amazon Basin, says ornithologist Dana Bradshaw, a research biologist at the Center for Conservation Biology located at the College of William and Mary.

As they travel, flocks stay in chimneys they may remember from previous trips. (These sites tend to be near bodies of water, where insects are plentiful.) Scientists believe the birds may stay in one area for several days to bulk up on the food they will need for the next stage of their journey. They may travel non-stop, day and night, in marathon pushes. Bradshaw suspects swifts leap-frog cities: Birds roosting in chimneys in Richmond, for instance, may have come directly from chimneys in New York.

Once upon a time, chimney swifts roosted in hollow trees. When Europeans first colonized America, they called the birds American swifts or American swallows. Later, as the forests disappeared into towns and cities, the swifts began frequenting chimneys -- and folks began calling them chimney swallows. Only later did scientists recognize and rename the bird as chimney swift.

Now, their chimney shelters are also disappearing. Over the last 30 years, many property owners have inserted smooth tile or metal sleeves inside their chimneys, a safety modification which makes stacks inhospitable to swifts. In addition, many of the old schools, churches and community centers which the birds use have been demolished or refurbished -- their chimneys sealed off for central heating and air.

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