Its a bat, its a plane, its a … Vauxs Swift!

Weekend!Events: Bird Watching

Just as many New Yorkers have never visited the Statue of Liberty, Portlanders often put off seeing the annual aerial acrobatics performed by the world's largest known roosting colony of Vaux's Swifts.

The small, black, batlike birds traditionally nest in hollow trees, but as old-growth forests diminish, the industrious avians construct twig and saliva nests in chimneys.

Year after year, about 35,000 Vaux's Swifts choose Chapman Elementary School's chimney to reside in until the end of September when they migrate to Central and South America.

According to one perennial swift watcher, Justin King: 'Usually a few (swifts) flutter around and then into the chimney first. Then, suddenly, there's a blanket of them making high-speed descents.' Once, King watched a petite swift get picked off by a peregrine.

Many observers bring blankets and picnics to enjoy sunset while they wait for nature's free show. The birds leave on their own schedule so times and ending dates are approximate, but Audubon Society-trained volunteers will answer questions whether the birds are flying or not.

- Brooke Myers

About 7 p.m. nightly, through Sept. 27, Chapman Elementary School, 1445 N.W. 26th Ave., 503-916-6295,