Night Songs in Autumn
By Dawn Gelderloos
It’s time for Field Notes, brought to you by the Montana Natural History Center.
As the days grow shorter and nights turn cooler, I find myself drawn outdoors at sunset. It isn’t the quiet I’m called to, but the enticing sounds of autumn. The loud chirping of crickets, katydids, and cicadas feels like an invitation. An audible changing of the guard as summer slides into fall. I always have mixed feelings about the loud chorus coming from the fields and trees. After long and hot summer days I feel a sense of relief from cooler temperatures, the turning colors of larch, oaks, mountain maples. And yet, the waning of summer and the arrival of fall also brings a hint of regret, sadness even, as the long summer days seem to slip away.
Here in the Nine Mile Valley west of Missoula, a distinct chorus of insects, once faint and now emphatic, seem to announce the change in store. I’m often caught by surprise by this resounding cadence. But I’m quickly drawn in as the land comes alive with song.
I learned recently that most of the chirps and trills resound from two orders of insects: orthoptera (crickets, grasshoppers and katydids) and homoptera (cicadas). It takes a well-trained ear to distinguish between so many songs. I am only just beginning.
While cicadas buzz on hot summer days, chirping crickets are often symbols of late summer and early autumn. And raspy katydids pierce the night during the late summer and early autumn.
According to the Montana Field Guide, the field cricket and the tree cricket are the two most common kinds of crickets in the area where I live. The fall field cricket, commonly heard chirping in fields, grassy areas, and near buildings, is a medium to large black cricket, about an inch long. Its song, a rhythmic “chirp-chirp-chirp” made by rubbing its wings together, can be heard in the afternoon and into the night. They are often attracted to warm areas and hide out in cracks and crevices. I’ve even found one or two chirping in our garage.
Montana is also home to several tree crickets. In general, these insects are known for their slender and pale shape and long and delicate antennae. As you might suspect, they live in trees and shrubs. Their notable song, a high-pitched trill, is often heard at night. Katydids, on the other hand, can be greenish in color, their song a continuous buzz that can last for up to 30 seconds.
So, why the resounding chorus? For most of these insects, autumn is the end of their adult life cycles. Their loud chirps are final mating calls as males desperately try to attract a mate before the season’s first frost.
While the adults die, their eggs survive the winter underground to hatch in the spring. Many of these vocalists can be heard into October or November depending on fall temperatures. Some studies show that many species have been expanding their range north in search of cooler conditions as our climate continues to change. How this could alter the sounds of autumn and the ecological role these insects play in biodiversity is still uncertain. As cold-blooded insects, crickets, for example, are sensitive to changes in temperature. While some species thrive in warmer conditions, extreme heat can be detrimental. Crickets chirp faster as temperatures rise and serve as a temperature gauge on hot days. And as the temperatures begin to fall, their chirps begin to decrease as well.
As I listen to the night chorus this year, I realize that I have a lot to learn and observe if I want to identify the rich diversity of autumn singers all around us. They are reminders of the change ahead. Autumn’s nature notes. Their grand and final chorus point us to a new season.
I’m Dawn Gelderloos for Field Notes, brought to you by the Montana Natural History Center, providing natural history education for schools and the public throughout Montana. For information about upcoming events and programs at the Center, call 406.327.0405, or visit our website at MontanaNaturalist.org.
