The swirling mass of small birds grew in number as the darkness deepened. More and more gathered, now numbering in the thousands, until as if on cue, they spilled into the chimney to cluster near the base stacked tightly, clinging to the wall for another night of rest before the long migration to Mexico.
Vaux’s swifts, like their cousins, the chimney swift of eastern North America, put on these spectacular displays each year in late August and early September. It’s not entirely clear why they mass before migration. While they tend to migrate in flocks, the migratory flocks are much smaller, and the large aggregations disperse over a week or more.
Although this small aerial forager looks quite a bit like a swallow, swifts are more closely related to hummingbirds. They are dark brown, very fast, and have a more fluttery flight than swallows. In part this is due to very short arms and large hands.
In the past, Vaux’s swifts depended on broken-off hollow trees in our forests as places to roost and nest. Rot is part of a healthy forest. Tree death is part of a healthy forest. It is important to remember that a forest is made of a great many more species than just its trees.
As our forests have been harvested for lumber and fiber, hollow snags have become fewer and less common. The young trees planted to replace those harvested are managed closely to produce healthy fast-growing trees, largely free of defect.
The loss of roosting and nesting habitat for swifts in the forest has been partially offset by the construction of chimneys. Chimneys are similar to dead, broken, hollow trees in many respects, and Vaux’s swifts have been quite happy to adopt this new feature in their habitat. I have been fortunate to have a pair of swifts nest in the chimney of my house for many years.
However, it does not end there. Newer construction caps and screens chimneys. This renders them inaccessible to swifts. And many older chimneys are also being capped. Consequently, swifts are finding fewer and fewer opportunities to roost and nest.
Structures used for pre-migration aggregations are even rarer. I am aware of only four locations in the Rogue Valley, although I’m sure there are more. The largest by far is the large chimney on the campus of Hedrick Middle School. For a few weeks in late August and early September each year, swifts gather in impressive numbers each evening to roost, and the spectacle now attracts the public.
Recently, a celebration was held at Hedrick to introduce the public to the unique event. There is the real possibility that this special site will be lost. The Rogue Valley Audubon Society with assistance from the Southern Oregon Land Conservancy is working to protect this valuable roosting site. The goal is to raise $250,000 to install a new boiler at Hedrick that will allow the old chimney to stand undisturbed. If you are interested in supporting this cause, visit the Rogue Valley Audubon Society website at http://roguevalleyaudubon.org/.
Stewart Janes is a biology professor at Southern Oregon University. He can be reached at firstname.lastname@example.org.