Towheeblog

McMinnville’s Vaux’s Swifts are on air (live, not broadcast) nightly in this season.  They need no rehearsals.  They fly and dance and twirl, appear and then vanish over horizons or up into the beyond.  After much twittering (which my wife can hear, I can’t) their circling grows tighter, and then a few, followed by many, begin to funnel down into the chimney which is their overnight lodging. To me their performance is a pantomime, all action.  It is modern dance mixed with tornado aesthetics.  You might suspect they have been studying all those satellite images of Hurricane Dorian.  Such is their  circular pattern though they often seem to alter it into a figure-8.  And they make sudden turns and swerves that no hurricane model ever imagined.

The descent began last night at 802 PM, finished at 809 PM when the final two stragglers fluttered down into the old brick stack.  About two hundred birds.  By 8 PM we had also seen at least 20 big brown bats go past,  making a far straighter path at a lower elevation than the swifts.

Swifts are known to feed as high as 3000 feet above the earth, gobbling up aerial plankton–small insects and spiders on streamers lifted into the sky by wind and air currents.  Swallows feed up there as well. On migration swifts can fly as high as 10,000 feet, often seen by people in small planes.
Watching the pre-roost flights of this local swift flock you may watch the sky and see nothing, then suddenly birds are appearing before your eyes.  I assume they plummet down in a dive and instantly become visible when their distance above you hits the magic point when your eyes can pick them out of the darkening blue.  Here is image of the flocks as blurs high in sky before they approach  chimney which reaches less than thirty feet above the next-door parking lot:

For more on swifts: “The swift is one of the least understood and most mysterious birds… They do have this ability to fly at high altitude for incredibly long distances, but this research has helped to unravel how they achieve the results that they do.”

“Swifts feed almost exclusively on the aerial plankton of flying insects and airborne spiders of small to moderate size.”

Much of this research has been done on Common Swifts, found over much of Europe and as large as our eastern Chimney Swift.