Toward Singing Insect Monitoring: Wall of Sound

by Carl Strang

A few days ago I began addressing the challenges to developing a monitoring protocol for singing insects. The biggest single difficulty is, as I described, differences in peoples’ ability to hear different pitches of sounds. Frogs and birds, the other organisms monitored by their songs, vocalize well within the hearing range of most people. Not so with singing insects.

It takes time to learn to recognize the various songs, but a learning period is part of every monitoring program. Also, monitoring will need to be done day and night because different species sing at different times. Apart from these relatively straightforward aspects, there are at least two other difficulties to overcome that are peculiar to singing insects. One of these is the lack of a vocabulary for describing insect songs. This will come with time, as different people come up with creative ways to communicate. For instance, several times I have heard people likening the tick-and-buzz pattern of the generic meadow katydid song to the sound of a sprinkler set to bounce back rhythmically to its cyclic starting point every few seconds.

Carolina ground cricket, one of the contributors to the wall of sound (though not this particular female, of course).

The final challenge is what I call the wall of sound. This is especially true at night, when the greater number of species and especially of individuals all are singing at once. In particular, many of the common tree crickets and ground crickets have more or less continuous trilling songs that blend to produce a collective mass sound that seems largely undifferentiated. I have a solution that works for me, and perhaps it could be made part of a protocol. When I do my block counts at night, I count only those individual singers that are close enough for me to distinguish clearly as I walk along. I ignore the wall of sound at large. For the most part this gives me a good sample of the species producing that wall, along with the others whose songs are more easily distinguished.

Singing black-horned/Forbes’s tree cricket, another element of the wall.

This isn’t a neat and perfect solution, however. Some of the long-trilling tree crickets have songs that cannot be separated from one another by ear. Others, and I am thinking here specifically of Davis’s tree cricket in my area, usually sing high enough in the trees that their songs are completely buried. Individuals can be distinguished only on the rare occasions when their song perches are low in the canopy (in such cases the Davis’s song is low enough in pitch to stand out).

As should be clear by now, if a singing insects monitoring program is to be comprehensive, it can’t be based on point counts, as is the case in breeding bird surveys and frog monitoring. It will have to be based on a route, as in dragonfly or butterfly monitoring. In conclusion, I think the elements are in hand to produce a workable protocol for a singing insects monitoring program. The main thing missing is enough people sufficiently interested that they will put in the time to learn the songs. Tomorrow I’ll suggest a learning program that will help people to learn insect songs in readily digestible stages.

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