A horrific loss of North American bird life has been documented in a yearslong study that recently made headlines.

That study showed almost one-third of our birds have disappeared in the past 30 years. But the loss of insect life has been even worse. In some cases this worldwide situation has seen the population of some insects reduced by more than 90%.

Now comes one explanation, research showing a family of agricultural insecticides extending their reach far beyond farm fields and home gardens.

The diet of many birds is based on insects. Loss of insects equates to loss of birds.

A summary of a recent research paper on neonicotinoid (neonic) insecticides was published Aug. 6 on the National Geographic Society website (nationalgeographics.com). The source of the paper was the online journal PLOS One (journals.plos.org).

The paper examined the amount of neonics applied to control insects that damage many crops — soybeans and corn in particular.

Neonics, which are chemically similar to nicotine, affect the central nervous system of insects, leading to paralysis and death.

There was, according to the authors of the paper, a 48-fold increase in agricultural use of these insecticides between 1992 and 2014, as farmers switched from an older class of pesticides to which some insects were developing resistance.

While we have not seen a 48-fold decrease in bird populations during that time, we now know of the huge decline documented in the newly announced study.

Many birders would say they did not need a formal research project to identify bird losses. On many days watching birds has become looking for birds.

Neonics kill honeybees, bumblebees and many species of wild bees. Research has linked the decimation of honeybee populations to neonics. Bees were used in this recent bird study as an indicator for other insects.

Insects die from ingesting neonic chemicals or by contact with them. Neonics do not discriminate among insects when it comes to effectiveness. Beneficial insects die along with those considered pests.

Neonics' impact is not confined to insects, the study states. Birds, fish, lizards — all animals using insects as a major source of nourishment — suffer.

Before neonics came to market, organophosphorus insecticides were in wide use. They too were highly toxic, but had half-lives of less than 30 days. (Half-life is the time required for any concentration of a substance to decrease by half.)

Neonics have half-lives of 50 days or more, extending their lethal impacts. Neonics used on trees and vines can remain effective for months or years, according to the research.

Besides persistence, neonics applied to crops do not stay where they're put. They "have a greater potential and tendency to move off-site unchanged into surrounding fields, land, surface water, and other waterways …" the report states.

Pesticides run off into wetlands, lakes and streams. They leach into groundwater. They drift as dust or spray during aerial application.

Insecticide is left in the soil when seeds coated with the chemicals are planted.

Neonics are highly water-soluble and persistent, the report says. "Their potential for off-site impacts on aquatic organisms is high."

Airborne field dust containing neonics is "potentially an important source of exposure to beneficial insects," the report states.

This increase in use "is consistent with the reduction in beneficial insect and insectivorous bird populations in recent years," the paper states.

Neonics aren't just a farm field phenomenon. They may show up in gardens, either through pesticides bought at a garden center or on plants from a commercial grower that uses the pesticide.

Ask your garden center whether they know if nursery-grown plants were treated with neonicotinoids. Watch pesticide labels on home garden products for ingredients like imidacloprid, dinotefuran, clothianidin and thiamethoxam, all of which are neonicotinoids, according to the Xerces Society for Invertebrate Conservation. For more information, visit nwf.org (search for "nixing neonics").

Companies registering new agricultural pesticides are required by the government to show that use of the product "will not generally cause unreasonable adverse effects on the environment," the paper states.

The author understates that existing regulations are "not yet adequate."

The organophosphate pesticides used prior to neonics had fewer adverse environmental effects, according to the author of this paper, who says, "The introduction and increased use of neonics … appears to be an example, in hindsight, of a regrettable substitution that might have been avoided …."

Regrettable indeed.

Read Jim Williams' birding blog at startribune.com/wingnut.