It's known worldwide as the windshield phenomenon. I hadn't heard of it until I went online in August after a trip to Grand Marais, Minn.
We had driven over 500 miles, collecting only four insect smears on our windshield. I remember trips when I had to stop at a filling station not for gas, but to clean a windshield covered with flattened bugs.
I couldn't recall when that last happened. The change was insidious.
Insects, according to researchers, are disappearing in a way similar to the disappearance of birds, only more so. The decline is constant, but so slow as to be unrecognizable until, suddenly, with one focused look it's all too apparent.
For a long time we have blamed habitat loss as a major reason for declining bird numbers. That certainly is a factor. But what if loss of insects is a major factor?
Bob Janssen, who lives in Golden Valley, for decades has been an observer of Minnesota birds and changes to bird population. I asked him if he knew anything about an insect problem here.
"Look through your windshield," he said. "That will tell you a lot." Dead bugs on summer windshields are a thing of the past, he said. He shared concern for bird species that rely on insects for food.
Recent studies in Canada focused on a perceived reduction in tree swallow numbers. That species feeds exclusively on flying insects.
"Birds are very resilient," Janssen said, "but they can't get along without food."
The cover story in a recent issue of the New York Times Sunday magazine called this decline "an insect apocalypse." The story recounts study after study documenting steeply falling insect populations.
Dramatic insect declines around the world were documented in a mid-October report published by the National Academy of Sciences.
Birds are not alone — the populations of other animals that eat insects are declining as well, the report said.
In a Puerto Rico study, undertaken in 2012, the decline of birds species eating insects closely followed a decline in the number of insects. Birds whose diet is mainly fruit or grain showed no corresponding decreases.
Data from that study in Puerto Rico were compared with data from 1976. The abundance of insects had fallen by 99 percent.
Scientists attribute the decline in Puerto Rico to an increase in forest temperatures of just under 4 degrees F. over the past 40 years.
That seems like a small increase. The researchers explained that insects long ago adapted to an unchanging range of temperature. They don't do well when temperatures exceed the norm.
Unlike animals, bugs cannot regulate their internal temperatures. This can impact reproduction. Sperm counts lessen, and sperm lose motility. The loss cascades, generation after ever-smaller generation.
Studies in Britain, Germany, Singapore, Costa Rica, Brazil, Mexico and Australia also found insect declines. Three of the studies gave climate sensitivity as a specific reason for decline.
In Minnesota, about a quarter of our resident summer bird species are threatened with the need to move north as the climate warms, according to Minnesota Audubon.
If insects move north to find suitable temperatures, birds would follow. This assumes, of course, that the move would accommodate insect needs.
Our songbirds eat either seeds or insects. Some birds also eat fruit. But almost all songbirds rely on insects to feed recently hatched young.
Insects offer the high protein and fat content necessary to support rapid growth of nestlings. Birds must be mature enough to care for themselves before fall migration or winter. Insects are the fuel for this race.
The Puerto Rico study ruled out the likelihood that habitat change or pesticides were major influences in the declines.
Meanwhile, a clean windshield gives you a good look down the road, and also, at the rate we're going, into our future.
(For information on the Puerto Rico study go to https://www.the-scientist.com/news-opinion/huge-arthropod-declines-documented-in-puerto-rican-rainforest-64954. The Times article is at https://nyti.ms/2RE6JCL)
Read Jim Williams' birding blog at startribune.com/wingnut.
