The Chapman Swifts are part of a migratory population of Vaux’s Swifts that roost seasonally in the chimney of Chapman Elementary School in Portland, Oregon, USA. It is North America’s largest concentration of Vaux’s Swifts.
Every evening from mid-August to mid-October, thousands of swifts gather in the sky over the school shortly before sunset. Count estimates of 1,700 to 35,000 swifts have been reported. Shortly after sunset, over a period of 10 to 30 minutes, they fly into the top of the brick chimney (constructed c.1925) to roost on the interior surface until they depart at sunrise. The school is on the birds’ migratoryroute to their wintering sites in southern Central America andVenezuela.
Last year I watched a hawk swoop down and grab a swift just as the flock was descending into the chimney. Suddenly, the whole flock of swifts stopped their descent and began chasing the falcon through the evening sky - just a massive black swarm of birds pursuing a single falcon for I’d guess ten solid minutes before reforming their cyclonic descending pattern to enter the chimney.