NEONICOTINOIDS AND UPPER MISS ECOLOGY

NEW THREAT EMERGES FOR MISSISSIPPI RIVER BIRDS:

OUR NATIONAL BIRD’S IMPERATIVE

La Crosse Tribune, Winona Daily News, 1-4-2025

Now that President Biden has officially designated the bald eagle as our national bird, we can honor its legacy and ban neonicotinoid pesticides.

I moved to the upper Mississippi River 45 years ago, drawn by superabundant birds on summer evenings. Black terns dove delicately for minnows, and great blue herons and great egrets flew continuously by banks here at Winona, Minnesota. During twilight, common nighthawks joined hundreds of swallows in a midair dance of aerial insectivores–birds who catch bugs primarily while flying. The nighthawks’ sharp nasal calls resounded numerously above the river. Their wings boomed, sounded like fluttering wind, then clapped as they flew herky-jerky flights all the way to sunset colors upriver, to darkness downriver, and around street lights throughout town. Now I see virtually no nighthawks during breeding season. Except for shrunken colonies of cliff swallows and a few other swallows, the river’s superabundant congregations of summer insectivores here has ceased. No bats. No terns either. Herons and egrets only by ones and twos.

Nighthawks demonstrate the complexities of bird declines. They nested successfully on gravel roofs in cities for decades, but now rubberized roofs no longer camouflage the eggs and may get too hot for eggs to survive. Predators who thrive in cities, e.g. crows, eat chicks. Pesticides in general diminish insect prey. Nighthawks also nest in grasslands that are greatly reduced, says Gretchen Newberry in The Nighthawk’s Evening. Scientists don’t fully understand nighthawks’ life on wintering grounds in Central and South America, but they’ve honed in on bird losses and neonics’ risks. The journal Science has estimated North America lost nearly three billion birds since 1970, about 29% of their abundance just five decades ago, with insectivores suffering the worst losses.

Neonicotinoids are a class of pesticides that are neurotoxins and systemic, are absorbed by crop plants to protect them from insects. Unfortunately, neonics move readily with water, persistently leave plants and leach into soil. Neonics inevitably reach wetlands, including the Upper Miss, where a National Academy of Sciences paper reported a 52% decline of burrowing (Hexagenia) mayflies, 2012 to 2019.

Shawn Giblin, water quality specialist with the Wisconsin DNR, considers mayflies a “no-nonsense ecological indicator” of the Mississippi. He and partners sampled ten tributaries and ten Upper Miss dam sites 2021-2023 and found neonics in 95% of the sampling locations. He and partners also analyzed mayfly tissue from five field stations on the river and one along the Illinois and found two of the neonics most toxic to mayflies—clothianidin and imidacloprid—in 100% and 59% of the samples.

Scientists find that neonics kill mayflies outright, and sublethal concentrations decrease their nymphs’ ability to burrow into the river’s bed. Neonics’ neurotoxins may agitate nymphs, cause them to leave burrows and suffer high predation rates, says Giblin (bad news also for fish who depend upon mayfly nymphs to convert organic detritus into food consumed all year).

Mayflies and other aquatic insects are more nutritious than other insect prey. They’re linked to fledgling success in insectivorous birds. The Academy of Sciences paper calculates annual hatches on the Western Lake Erie Basin can provide “12 trillion calories of food resources—enough to meet the energetic demands of over 53 million nestling birds from fledgling to hatchling.”

American Bird Conservancy says birds die outright when they eat neonic-coated seeds. Coatings can fly off as dust, impair and kill bees and other pollinators. Neonics can prevent and diminish the emergence of butterflies and moths and have been shown to damage birds’ immune and reproductive capabilities, cause sudden weight loss, and foil abilities to navigate and migrate.

Neonics are everywhere, used on corn, soybeans, cotton, cereal grains, lawns, gardens, golf courses, parks, commercial landscapes. They’re detected in tap water and non-organic produce. The U.S. Centers for Disease Control and Prevention found that at least half of the U.S. population gets exposed to neonics. The Natural Resource Defense Council claims neonics are linked to “neurological, developmental and reproductive harms, including birth defects of the heart and brain.”

Alternatives exist, says American Bird Conservancy. In 2015, the Province of Quebec started to require corn and soybean farmers to apply for prescriptions—to show a definite need—to use three especially toxic neonics as seed treatments. Eight years later, only 0.5% of Quebec’s corn and no soybeans used neonics. No shortage of the products occurred. Large-scale row crops didn’t need neonics.

I saw no bald eagles on the river 45 years ago. They’d mostly disappeared from our contiguous 48 states by 1970, largely because DDT impaired reproductive biology. We banned DDT in 1972, removing the pesticide from food chains. Now bald eagles breed by the hundreds on the Upper Miss. They’ve recovered throughout America, as declining birds and insects might. The ban also greatly reduced humanity’s exposure to carcinogens.

 

Richie Swanson birds and writes in Winona, Minnesota, RichieSwanson.com. His sources here include the journal Environmental Pollution 238 (2018), Wisconsin Neonics Forum 2024 and Cornell/Lab Birds of the World.

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