Counting a Tornado: How We Count the Vaux’s Swifts

By Candace Larson, Field Biologist and Trip Leader

The Vaux’s Swift spectacle in September is an annual highlight for many Portland area nature lovers. Thousands of migrating swifts gather at dusk each evening and form a bird tornado as they enter the Chapman Elementary School chimney to roost for the night. Bird Alliance of Oregon provides fun and informative on-site interpretation for the public throughout September. And, impossible as it might seem, we also count these birds every night during fall migration. Our data helps us track local trends, and also contributes to a larger database of swift counts from BC to Baja.

Community Scientists count the Vaux's Swifts at Chapman Elementary School
Community Scientists count the Vaux's Swifts at Chapman Elementary School

So how do you count a swirling mass of thousands? It’s easy: just count the wings and divide by two! (Dad joke, sorry.) Actually, counts are conducted by a team of two trained observers who meet at the site before sunset and settle into a perch with a good view of the action. One observer locks their binocular view onto the chimney rim and readies a hand-held clicker counter. As the birds drop in, this observer clicks for each block of 10 swifts. The second observer keeps a birds-eye view on the sky, scanning for raptors and documenting any predation events. They also inform their teammate of new flocks forming or leaving, and record all the data. It takes practice, especially at the peak of migration when swifts can number up to 15,000! Our awesome volunteer corps is up to the task.

If you are interested in Bird Alliance of Oregon’s swift counts, this infographic contains a useful summary of our annual efforts. Our counting teams are established for the 2019 season, but we welcome (and train!) new volunteers every year. You can follow along with the action as we post our nightly swift counts at Chapman to the website.