A CLOUD OF VAUX'S SWIFTS

Last Saturday evening a few minutes before sunset, Patty and I opened our camping chairs and settled down to watch a strange phenomena. Unfortunately, it was a heavily overcast evening and I fear we may have not observed the event at its best, but we were still fascinated by a few highly unusual minutes of birdwatching. The tiny swift, no larger than a sparrow, is in several ways an oddity in the bird world. Lacking the rear "toe" and thus unable to perch on a branch, this tiny bullet of a bird remains in flight literally from sunrise to sunset. It feeds on insects which it catches in the air while flying about and can capture as much as half its own body weight every day. That alone makes the swift a valuable asset in city or countryside habitats alike.

When evening comes, however, local flocks of swifts need to find a sheltered place to spend the night. Hollow trees are ideal, but there are far too few trees to accomodate the enormous numbers of birds which come together in summer evenings. To solve this problem, eastern swifts have adopted the practice of using chimneys; thus its name "chimney swift" in mid-west and southern states. Our local variety, the Vaux's swift has adapted that practice to large "industrial-sized" chimneys and unused smoke stacks. Somehow they are able to cling to the rough interiors in great numbers and rest overnight in safety. In northwest Portland, there is just such a large chimney at an elementary school site near the Nob Hill neighborhood. In late August until the first week of October the birds use this particular location for evening housing, and not just a few birds: thousands of birds home in on the site at sunset - many, many thousands... according to a newspaper report, as many as an estimated 35,000 in recent peak years.

As the time approaches, the gathering cloud of swifts rapidy circle again and again rounding the stack hundreds of times as more birds continue to arrive from every direction joining the thickening masses. As the hoard begins to swirl around and past the top opening of the chimney stack, birds begin dropping into the stack by the dozens. At every pass large numbers, perhaps scores, of swifts drop into the chimney interior for the night. On a sunlight day I understand this phase only lasts a few minutes. Since our particular evening was so heavily overcast the process seemed to be more gradual, perhaps because the birds could not determine the exact minute of sunset. Still, over a period of about forty minutes, the entire host of birds seen earlier in the sky somehow managed to fly into the chimney to spend the night. It was astounding, and it thoroughly delighted the 300 or so folk watching. In fact, as the last seen bird disappeared down the stack, a loud round of applause broke out on the hill above us and passed through the crowd behind us all the way to the tennis courts to our north.

Thinking about this peculiar event raises a number of interesting questions. How do so many birds, even as small as is each is, manage to find "clinging room" in such relatively crowded quarters simultaneously? Where do these birds spend the rest of the year since their range is only from Central California to northern British Columbia and from eastern Oregon and Washington to the Pacific Ocean? How do they know where and when to gather? how can they fly all day long and still maintian such precision in formation at the end of the day? How is the order of entering the chimney determined? And finally, can anyone not consider this amazing event a wonder and a miracle?