I found your article and recording fascinating. Thank you for sharing!! Martha Jones, Arvada, Jefferson County
On Monday, September 9, 2019 at 11:43:26 AM UTC-6, Ted Floyd wrote: > > Hey, all. > > One of my favorite locations in spacetime is nautical twilight > <https://www.timeanddate.com/astronomy/nautical-twilight.html> in > residential and urban districts in the Front Range metro region in early > September. The plains harvest flies, *Megatibicen dealbatus*, have > largely quieted down by that time, leaving the Twilight Big Three (TBT) to > do their thing. The TBT are: the low-frequency snowy tree crickets, a.k.a. > "thermometer crickets," *Oecanthus fultoni*; the mid-frequency fall field > crickets, *Gryllus pennsylvanicus*; and the high-frequency greater > angle-wing katydids, *Microcentrum rhombifolium*. Here's the sound of all > three of them going at once: > > https://www.inaturalist.org/observations/32419411 > > I made that recording in Lafayette, eastern Boulder County, at 8:18 pm on > Sat., Sept. 7. 2019. The temperature was 71 degrees Fahrenheit. Key point: > I was in a residential district, away from the marshes and meadows of, say, > Greenlee Preserve, where many other orthopterans join the fray and > complicate matters. This is the sound of the city (also the sound of the > suburbs) in the region. Call it the symphony of the city. The snowy tree > crickets have a distinctive, musical, pulsating quality; count the number > of chirps in 15 seconds and add 40 and you have the temperature in degrees > Fahrenheit. The fall field crickets are higher and shriller, the classic > "nothing but crickets" of 20th-century television and movies. > (21st-century, too, perhaps, but I haven't watched TV since about 1990. I > hear there's something called flatscreen and reality shows??) And the > greater angle-wing katydids are the spooky "clicky night bugs," like a > little ghoul--a DIA lizard person, perhaps--chattering its teeth in the > treetops. > > I find spectrograms to be useful for understanding and enjoying natural > sounds, so here's a spectrogram of the recording above: > > [image: Orthopteran symphony.png] > > The top panel is, in essence, a measure of how loud the sounds are. The > fascinating and--for me--somewhat depressing thing is that the katydids > (indicated by the vertical lines) are unbelievably loud. I don't hear them > all that well anymore. But my wife and kids tell me they are as loud as the > flickers that are slowly but surely denuding the house of its siding and > roofing. The steady pulses, barely visible above the baseline trace, are > the snowy tree crickets; and the baseline trace itself is the chorusing of > the fall field crickets. > > The lower panel is, if you will, the musical score of the orthopterans' > songs. A musical score is a plot of frequency against time (really! it > is!), and this lower panel is precisely the same thing. Different units and > scales, but it is trivial to "translate" from one notation to the other. > Anyhow, you can see the high clicking of the katydids (so-called "carrier > frequency" way up there just under 10 kHz), the mid-range trilling of the > fall field crickets (around 5 kHz), and the distinctively low-frequency > grinding of the snowy tree crickets (just under 3 kHz). > > There's a nice tutorial in the physic literature on all of this, although > applied to the songs of common American birds, not orthopterans. The paper > came out just a week ago: > > https://aapt.scitation.org/doi/10.1119/1.5124271 > > Some of the content is behind a paywall. If you want the PDF of the full > article, please get with me backchannel, and I'll be happy to send it along. > > Or simply enjoy the songs, just as they are! Remember: low, pulsing = tree > crickets; higher, shrill = field crickets; very high, clicking = katydids. > And this: Listen in busy neighborhoods; tree-lined boulevards are the best. > > > Ted Floyd > Lafayette, Boulder County > -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/cobirds/dab4d30f-31f9-4c12-b787-a5491dedf5fb%40googlegroups.com.
