We just received word that four roosting sites for the Vaux’s Swifts have been designated as Globally-significant Important Bird Areas by Audubon and BirdLife International. What’s unique about this designation is that, unlike the habitat areas that usually receive this title, these sites are actually man-made chimneys (above, Vaux's Swifts swarm around a building ni downtown Los Angeles earlier this year).

If you haven’t seen the migration of the Vaux’s Swifts through the Pacific Flyway, you’re missing out on one of the most fascinating spectacles of nature. After a day of traveling and feeding on insects, thousands of the birds will swarm around a particular type of old brick chimney for several minutes, finally sweeping into the opening. Inside, the birds will cling to the rough brick and sleep for the night, protected by sheer numbers and the narrow opening above. Typically, these birds would be using the hollow insides of dead or burnt trees – or possibly caves – for this roosting, but as these opportunities have been diminished due to habitat loss, the birds have adapted to the chimneys.

We received the word from Larry Schwitters, who is arguably the leading advocate for the species, tracking their migrations and numbers through the Pacific Flyway. The sites identified in the listing are in four separate counties in Washington State, and are identified by the buildings that house the chimneys: Monroe Wagner Elementary School, Joint Base Lewis McChord Building, Selleck Old Schoolhouse, and Old Northern State Hospital.

While the Vaux’s Swift, like other birds, migrates twice a year, the fall migration seems to bring about the truly spectacular sightings around these chimneys. During these fall months, people gather by the hundreds to see the swifts at sights from Washington to Oregon to Northern and Southern California.