If the answer is “flying cigars,” what do you suppose the question might be?
If you said something involving George Burns, Groucho Marx and an airplane, you’re gifted (or burdened) with the same weird sense of humor I have ... but you’d be incorrect.
A more suitable response, at least here, in a nature column, might be, “What is a fantastically appropriate nickname for those little sooty gray birds, the chimney swifts?”
Maybe it’s my love for an occasional Macanudo, or maybe it’s the remarkable aspects of their life cycle, but I just can’t help but love chimney swifts. Each spring these neotropical migrants make their way from South America to the eastern United States and southern Canada, with a flip trip in fall, flying as many as 4,000 miles each way on wings that measure a scant 12 inches across.
In our area from May through September, Chaetura pelagica spends its days flying around catching insects and its nights clinging to sheltered, vertical surfaces. You won’t see swifts perched in trees with other birds. Their short, weak legs and tiny, clawed feet won’t allow it. Nonetheless, chimney swifts are well adapted to their ecological niche – even though the setting for that niche has changed dramatically over the last 200 years.
Before European settlement, North American chimney swifts made their homes inside caves and hollow trees. But with the settlers came brick and mortar – and chimneys – and voila, a behavior shift was born. Today, chimney swifts are nearly 100 percent dependent on humans for nesting habitat – a predicament they share with another summer visitor, the purple martin. (You may recall hearing, purple martins in the eastern U.S. nest exclusively in martin houses erected by humans.)
Because of this similarity, and the way both martins and swifts devour insects, you’d be inclined to think the two species are related. But actually, the swifts’ closest relatives are hummingbirds. The resemblance may not be obvious, but if you can picture a hummingbird in flight, you can start to understand the relationship. Both birds share a similar skeletal structure that causes their wings to beat stiffly, shallowly – and rapidly.
In flight, hummingbirds look like miniature helicopters, darting and hovering, then occasionally resting on a convenient perch or twig. Chimney swifts, however, have a flight pattern that may be best described as erratic. It’s not that they lack direction, heavens no. To the contrary, their constant swerving and diving is directly related to the insect prey they capture, and consume, on the wing.
Thanks to this lasting stretch of warm weather and cool, but not frosty, evenings, chimney swifts can still be seen in our area, even though we are almost into October. But because their swooping after insects can take them far from their chimney roosts, their daytime locations can be unpredictable.
At dusk, though, if you’re lucky, you can see swifts by the hundreds swirling down into their chimneys for the night. The trick is finding the right sort of structure. Their preferred “habitat” is an area of older buildings that feature brick chimneys that are neither lined nor capped.
The Tri-Cities still have a few of these structures remaining. (There’s also a neat project underway to create chimney swift “towers,” but that’s another story for another time.)
What I was most surprised to learn though, just the other day, was that there are swifts roosting in the chimney of a place that I drive by almost daily: the Swanson Pool building at Pottawatomie Park in St. Charles. Alert reader Bruce Rowland noted that there are hundreds of swifts roosting there, in the chimney near the concession stand at the south end of the building.
Bruce emailed on Sunday and I went to check out the spectacle Monday. It began just before 7 p.m. and was over around 7:10. If you’d like to see for yourself, remember to adjust for our ever-shrinking amount of daylight and aim to arrive around 6:45. Pull into the lot on your right as you come down the Pottawatomie hill, and park in the spaces along the south side of the pool. Look up to the top of the building – at the chimney – and enjoy the show!
• • •
Last week’s column mentioned the sharp rise in numbers of white-lined sphinx moths in our area. Somewhere toward the end of the piece I mentioned there may be a relationship between last year’s drought and this year’s spike in moths, since the arid southwest often experiences population “explosions” similar to what we’re seeing.
Well, I was wrong.
This past week, I kept trying to make a connection between hot, dry weather and sphinx moths, which need plants for feeding, and soft ground in which they can pupate. Coming up dry, literally, I sent an email to Sam W. Heads, Ph.D., curator of orthoptera and fossil insects at the Illinois Natural History Survey in Champaign. In two easy sentences, Sam gave a very reasonable explanation for what we’ve been seeing:
“Hyles lineata is known to go through these population explosions every once in a while, sometimes to the extent of becoming a minor agricultural pest. As I understand it, these booms in numbers tend to follow periods of rain that encourage the growth of larval food plants.”
So there you have it. The sphinx moths we’ve been seeing lately, the ones that look like odd little hummingbirds hovering in front of flowers, owe their boom not to last year’s drought, but to the rains we experienced earlier this year. Thank you, Dr. Heads!
• Pam Otto is the manager of nature programs and interpretive services at the Hickory Knolls Discovery Center, a facility of the St. Charles Park District. She can be reached at 630-513-4346 or firstname.lastname@example.org.