Whine as though a pine tree is bowing a broken violin,

As though a bandsaw cleaves a thousand thin sheets of titanium;

They chime like freight wheels on a Norfolk Southern slowing into town.

But all you ever see is the silence.

— from the poem “Cicadas at the End of Summer” by Martin Walls, 2002

If you’ve been paying attention, you already know this summer’s second-most iconic sight in Butler County — the first-most iconic being rain, of course.

Right this moment, in sun-dappled parks and on shady lawns across the region, fat songbirds are feasting merrily on the piled-up carcasses of dead and dying cicadas.

They’ve been gorging for a few weeks now. The sparrows, robins, cardinals and grackles have become selective; pecking out the choice morsels like eyes and abdomens, they leave behind the legs, wings and other hard parts.

Why not? The buffet seems endless. Of course, we know it will end soon. Thank heavens!

This carnage happens just once every 17 years, when masses of periodic cicadas emerge, mate, reproduce and die in a matter of weeks. The larvae they produce will burrow underground and live on tree sap, then repeat the ritual like clockwork in 2036.

Here’s where a fascinating bit of scientific research comes into play.

Walter Koenig, a retired Cornell University biologist, studied bird populations from 1966 to 2010 and discovered population fluctuations that were synchronous to the cicadas’ 17-year life span.

Koenig and his co-author, Andrew Liebhold, an ecologist at the U.S. Department of Agriculture Forest Service in Morgantown, W.Va., analyzed avian population data from the North American Breeding Bird Survey from 1966 to 2010. The scientists targeted 15 bird species, including yellow-billed cuckoos, redheaded woodpeckers and house sparrows, which eat cicadas.

In a report published in 2005, Koenig and Liebhold concluded, these birds’ populations reached their lowest point the year the insects emerged, which suggests that avian predators aren’t exerting as much pressure on the cicadas as we might have assumed. Indeed, the research showed that 12 years after the cicadas’ emergence, the birds went into decline, eventually reaching their lowest point in year 17 — just when the cicadas were emerging again.

Our eyes tell us the birds are slaughtering the bugs; Koenig says the science shows us it’s the other way around.

“The cicadas are driving the birds’ populations; they’re setting the birds on a trajectory that leads to significantly lower populations at the time of the next emergence,” he says. The timing of the cicadas’ cycles is all about manipulating their predators.

As is often the case with science — true science — it’s a partial answer. Regarding the racket these bugs make, described by the poet Martin Walls as “a pine tree is bowing a broken violin”: does it interfere with the songbirds’ mating calls as some scientists theorize? How could they prove or disprove their postulate? And another study shows the enormous effect that the biomass of cicada carcasses has on the environment. It’s a massive nutrient enrichment of the soils trees, birds and other flora and fauna — one that sustains more than birds until the next emergence.”

The cicada still intrigues us, Koenig said in an interview published seven years ago, adding, “We still don’t have a good theory that explains how the cicadas’ resource pulse causes the birds’ populations to reach their low point exactly ... 17 years later. We’re still scratching our heads over that.”

Which is to say, there’s no evidence to suggest climate change has anything to do with it; and that uninformed manipulations of our environment, even with the best of intentions, might do more harm than good.