The Same Pesticides Linked to Bee Declines Might Also Threaten Birds

On a late spring morning, Christy Morrissey, a wildlife ecotoxicologist at the University of Saskatchewan, drove her mud-splattered pickup past an undulating sea of cultivated fields two hours north of Saskatoon. Now and then, the land rose to form low green hills, and the sound of aspen leaves rattling in tall-grass sloughs floated in the open windows. All the way to the horizon, shallow ponds, called potholes, punctured the landscape, each dotted with ducks and ringed with bulrushes and cattails.

After inspecting a map drawn by a student, Morrissey pulled to the side of the gravel road, grabbed a small cotton bag, and crept stealthily toward a wooden box nailed to a fence post. Like a pouncing cat, she clapped her bag over its round entrance hole, and then cautiously opened the box’s side door. Staring into the middle distance, she felt around inside. “Got her,” she said, extracting a glossy Tree Swallow and gently tipping her head-first into the bag. “Fifty percent of the time I can catch the female on her eggs.”

Back in her truck, Morrissey read the tiny silver band on the swallow’s leg, then carefully weighed and measured it. The data, together with that of nearly 500 birds, would help her compare the health of swallows that live near industrial-scale farms with those that live in grassland areas. Over the next couple of weeks, she’d also collect blood and feather samples from 12-day-old chicks to assess their stress levels and the quality and composition of their diet.

A century ago, the fields over which these birds swoop and dive were part of the largest grassland on Earth, stretching 276,000 square miles from Iowa to Alberta. Now oil seed and cereals cover much of southern Saskatchewan. The prairie potholes still host nearly 200 species of ducks, songbirds, and shorebirds, but more than half of these species are in steep decline, and only 30 percent of the region’s original wetlands remain.

“All of this is canola,” Morrissey said, gesturing in three directions as she drove to the next nest box. “And all of it is treated with neonicotinoids.” Neonics, as they’re known, are pesticides chemically related to nicotine that act as powerful insect neurotoxins. Although aimed at pests, neonics have been shown to affect pollinators, too; they’ve been linked to colony collapse disorder, which devastated 44 percent of American beekeepers’ hives between 2015 and 2016. Now, after five years of intense investigation, Morrissey suspects that neonics may affect a far broader and more complicated food web—one that starts at the bottom of ponds, entangles aquatic insects, and ensnares their ultimate consumers: grassland birds.

Typically deployed as brightly colored seed coatings, neonics may seem more innocuous than the pesticides they were designed to replace two decades ago. They are certainly easier to work with: Farmers simply sow the seeds, then sit back as the pesticide is incorporated over time into the plant’s roots, stems, leaves, and pollen. Pests munch on any of these parts, their nervous system goes haywire, and they keel over, dead. Because plants express neonics through all growth stages, farmers can eliminate one or more trips over their fields with a pesticide-filled sprayer, saving fuel and reducing the volume of chemicals applied.

Even as the amount of all pesticides applied to North American farmland has dropped in recent years, from 955 million pounds in 1997 to 789 million pounds in 2012 (the latest available data), the use of neonics has continued to grow. Considered cheap insurance for expensive seeds, they are now the most widely adopted pesticide in the world, with an expected 2018 market value of $4.2 billion. Neonic-treated corn, soy, and cotton cover 150 million acres of the United States, about a twelfth of the area of the lower 48. In Canada, neonics are used on 44 percent of cropland, including some 21 million acres of canola, the nation’s second-most-cultivated crop.

But their delivery system has a major flaw. “Only about 5 percent of the compound is taken up by the plant,” Morrissey says. The rest leaches off the seed, accumulates in soil, and sluices via snowmelt, rain, and groundwater seepage into ponds and wetlands, where insects like midges and caddis flies—a staple for billions of grassland birds—start their lives.

A 2015 study by the U.S. Geological Survey found neonics in 63 percent of water samples taken from 48 streams. In Canada, researchers detected at least one neonic—there are seven types on the market—in 91 percent of wetlands. Unlike many liquid pesticides, neonics can persist and accumulate in ponds for months, if not years. In other words, says the Center for Food Safety, a nonprofit that promotes sustainable agriculture, neonics are “almost tailor-made to contaminate the environment.”

Christy Morrissey grew up in Vancouver, dreaming of becoming a vet: She loved animals, and she felt at peace in nature. At the University of British Columbia, she took classes in zoology and ecology, but she also entertained thoughts of becoming an English teacher. “There was no culture of science among my family or friends,” she says, “and I had no female scientist role model at the university.” Then one day the renowned ornithologist Jamie Smith invited her on a field trip in the Okanagan Valley. Soon, she was spending lunches and weekends birding and evenings learning bird calls. “My mom thought I was nuts,” she says.

After graduating with a degree in zoology, Morrissey volunteered for the Canadian Wildlife Service to study raptors and carbamates, a class of pesticide now banned in Canada and the European Union. A pattern of sleuthing formed: For her doctorate at Simon Fraser University, Morrissey investigated how atmospheric pollutants got into mountain-stream food webs, then rippled up to American Dippers; as a postdoc, she tracked how arsenic—a treatment for pine-beetle infestations—affects woodpeckers and Osprey and how acid rain affects European Dippers.

In 2010, Morrissey accepted an assistant professor position at the University of Saskatchewan. Among the first people she called for advice on developing a research program was Pierre Mineau, then a senior research scientist with Environment Canada and an expert on the ecotoxicology of pesticides. “Study neonicotinoids,” he told her, without hesitation. Morrissey hadn’t ever heard the word. But she quickly learned that neonics are ubiquitous; that many dealers don’t sell seeds without them; and that crops, in many cases, don’t even suffer from the specific pests the chemicals target. “I knew that treating every seed in the ground, whether you need that crop protection or not, was a bad idea,” she says.

So with a small army of students, Morrissey designed a Hydra-like research program that is exploring, piece by piece, how neonics move from farm fields to waterways, how they affect the invertebrates that live there, and how these aquatic insects—their abundance, diversity, and health—in turn affect birds.

Late spring is a busy time for Canadian field biologists, and the morning after Morrissey’s survey of nest boxes, she joined one of her graduate students, Erin Maloney, in the grassy meadows of the St. Denis National Wildlife Area. As the pair topped a gentle rise, they gazed down upon the centerpiece of Maloney’s investigations: a small village of yellow-and-white teepees emerging from a cattail-ringed pond. The 21 limnocorrals, as they’re called, are helping Maloney figure out what effect neonicotinoids have on aquatic bugs.

The women climbed into an aluminum canoe and paddled out to the middle of the pothole, where a wide plastic sleeve stretched from the pond’s mucky bottom to a meter-square frame floating on its surface. Above the frame, netting rose to form a narrow funnel that dead-ended with a jar of ethanol. Different mixtures of neonics swirled inside each corral, along with pond-dwelling insects such as midges, damselflies, and mosquitoes. If they survived their aquatic phase, the insects would fly up and die in the jar. Maloney planned to compare how many adults emerged from corrals dosed with neonics to those in controls; she would also determine whether pesticide exposure shifted the population’s composition.

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In dozens of other studies that Morrissey analyzed for a journal article in 2014, scientists have found that neonics can affect abundance and survival of aquatic insects—even at levels below current U.S. water-quality guidelines. Still, those in the industry aren’t convinced. “I don’t think Morrissey has demonstrated that residues actually in the water from field applications are resulting in significant loss of aquatic invertebrates,” says Ray McAllister, senior director of regulatory policy at CropLife America, which represents pesticide manufacturers. “The levels are well below those of concern established by EPA.”

Morrissey and other researchers believe EPA guidelines—which are 30 times higher than those established throughout Europe and Canada—are out of date and too high. One reason: Neonic makers tested the compounds on Daphnia, a tiny freshwater crustacean commonly used as a model for ecotoxicological studies. But Morrissey has found that Daphnia is uniquely insensitive to neonics, while midges—the most common insect in prairie potholes—are especially vulnerable. Moreover, industry usually tests only for acute exposures to single substances, but aquatic invertebrates are continuously exposed to sub-acute levels of multiple compounds over long periods of time. Researchers have also discovered that while some insects survive neonics, their offspring may not pupate—an epic reproductive fail.

As she stepped out of the canoe and plucked three large ticks from her pants, Morrissey explained that midges are important prey for grassland birds, as well as aerial insectivores such as swallows, nightjars, and swifts. Not only can neonics reduce midge numbers, studies show they can also, at very low concentrations, cause adults to emerge 10 to 20 days earlier than normal. That’s a huge shift for an insect whose adult phase lasts just a few weeks, and it’s particularly bad for birds whose spring arrival, feeding, and nesting is timed with peak insect abundance. “Once the birds start to breed, they can’t move,” Morrissey said. “So this area becomes, for them, an ecological trap.”

Of course, Morrissey still needs to demonstrate a link between declines in insects and declines in birds. To that end, her team is measuring the abundance and diversity of insects near farm fields, wetlands, and pond surfaces. After three years, she’s found reduced insect biomass near ag sites that have higher wetland neonic concentrations. She also knows, from assessing the body condition of Tree Swallows, that chicks living closer to farm fields have about half of the body fat of chicks reared in grassland environments, and that their parents spend more time away from their nests, presumably hunting food.

But those two findings don’t establish cause and effect. So to find out whether insects delivered to chicks are contaminated—a key puzzle piece— Morrissey has devised yet another experiment. She extracts boluses of food from the gullets of Tree Swallow nestlings and analyzes them for 40 pesticides. She expects to have the results later this year.

While Morrissey has been methodically building her case, a team of Dutch scientists conducted a study, published in Nature in 2014, that seems damning. It found that populations of insect-eating birds have declined by an average of 3.5 percent a year—a statistically significant drop—in areas where the neonic imidacloprid contaminated surface waters, and the decline started only after the chemical was introduced in the Netherlands in the mid-1990s.

According to the 2016 State of Birds report published by the North American Bird Conservation Initiative, a coalition that includes the National Audubon Society, temperate grassland and aerial-insectivorous birds on this continent have declined 33 percent since the 1970s—the most rapid drop of any bird group. Using pesticide-impact studies and breeding-bird surveys conducted between 1980 and 2003, Mineau determined that an increase in all types of pesticides was, by far, the most plausible explanation for this decline. Nicole Michel, a quantitative ecologist with the National Audubon Society, found that populations of 17 bird species whose diets include aquatic insects declined an average of 1.3 percent a year over 21 years, due to a variety of factors. That may not sound like much, but Michel points out that it translates, over another 50 years, to a 48 percent drop. “We absolutely should be concerned about the possibility of neonic-related declines,” she says, “since birds are experiencing other stresses, too.”

François Messier farms 10,000 acres northeast of Saskatoon—half devoted to canola and half to barley and wheat. But despite the best efforts of seed marketers, he refuses to purchase neonic-treated barley and wheat seed. “I have no problem with wireworm,” he says—the larval stage of the click beetle, which feeds on the seeds and sprouts of these cereals. But canola is a different story. “I can’t grow it without the neonic. Flea beetles would destroy the crop in a matter of days.”

And so Messier now spends an extra $10 per pound of canola seed than he did a decade ago, when he foiled flea beetles by spraying a carbofuran, now known to be extremely toxic to birds. (Carbofurans are estimated to have annually killed up to 91 million songbirds in the United States during their peak use in the 1980s.) A retired University of Saskatchewan ecologist, Messier is, by training and by temperament, concerned with unintended consequences. He knows that carbamates are bad for birds, but he hasn’t yet seen any proof that their replacement—neonics—are too. He understands that the chemicals are washing into his ponds, and he’s even persuaded his neighbors to forgo their use on barley and wheat. But he’s not ready to give up on neonics entirely. “I want these companies to develop other compounds that are more environmentally friendly,” he says. For now, though, the flea beetles have him on the run, and neonics happen to be “very good at killing them.”

Soon, however, the Canadian government may relieve Messier of his moral dilemma. Because of the risk to beneficial insects, Health Canada last November proposed a ban on all agricultural uses of imidacloprid and a special review of the type of neonics that coat canola. Such concern is global. The European Union has restricted the use of three types of neonics, and in the United States the EPA has suspended any new uses of neonics while the agency assesses their impacts on bees. Meanwhile, the U.S. Fish and Wildlife Service, adopting a precautionary approach, is phasing out neonics on more than 150 million acres of public land, some of which is leased to corn farmers. The U.S. Forest Service continues to apply them to about half a million acres (out of its 193 million) to combat invasive insects that threaten trees.


While commodity farmers use the vast majority of neonics in North America, gardeners and groundskeepers have come to rely on them as well. Nurseries treat plants with neonics, and homeowners apply them to lawns and gardens. But even this use is in decline: In response to societal concern for bees, many states have proposed bans on the residential use of neonics, and scores of cities have banned or minimized their use on municipal property. Lowe’s, Home Depot, and other garden-supply stores are shunning the chemicals. And ScottsMiracle-Gro is removing neonics from eight of its Ortho-brand products used to treat flowers, trees, and shrubs. “Our decision wasn’t science-based, because there continue to be different points of view,” says senior vice-president Jim King. Rather, the company is betting on eco-friendliness being good for business.

Morrissey has specialized in studying the indirect impact of neonics on birds, but the compounds have direct effects as well. Mineau has shown that as little as one corn seed coated with imidacloprid can kill a bird the size of a Blue Jay. CropLife’s McAllister acknowledges this finding but doesn’t think it happens much. Farmers are instructed to quickly clean up spills, he says, and he calls birds digging up planted seeds “an insignificant or nonexistent problem.” Morrissey disagrees. “Birds are attracted to farm fields,” she says. “We’ve counted more than 20 species occupying and feeding and habituating fields immediately after seeding.” Asked why freshly planted fields aren’t littered with bird corpses, Morrissey cites studies that show carcasses are scavenged within six hours of sunrise.

To learn more about what happens when passerines consume neonicotinoids, Morrissey’s postdoc Margaret Eng captured 60 White-crowned Sparrows, seed-eaters that migrate through Saskatoon at night. Over a frenetic four-week period, Eng tested the sparrows’ ability to orient themselves for migration—a crucial skill that other studies have found is impaired by organophosphate pesticides.

After ascertaining that her birds were in a state of zugunruhe, or migratory restlessness, Eng placed each of 12 sparrows in a wide mesh-covered flowerpot. Then, well before sunset, she drove the birds to an open field far from artificial light, placed the pots beneath infrared video cameras, and retreated from their field of vision. Free-living migrants hop and then fly in a northward direction after the sun sets; Eng’s birds hopped in that direction, too.

Next, Eng orally dosed a group of birds with imidacloprid at either one tenth or one quarter of the reported lethal dose for House Sparrows and again brought her birds to the field before sunset. By then, though, nearly three days had passed, and many had grown lethargic and lost an average of 25 percent of their body weight. “That was a surprise,” Eng says, “because we weren’t looking for toxicity but subtle sub-lethal effects.” Over the next two weeks she repeated her field trials three times.

Eng’s preliminary analysis showed that birds given either dose hopped in all directions. This result suggests that imidacloprid causes disorientation, which could potentially delay migration or alter migratory direction. “There is virtually no published data on effects of neonics on small, wild songbirds, which greatly limits our ability to safely regulate these chemicals,” Morrissey says. Experiments like Eng’s, then, are “critical for understanding the effects of widespread insecticide use across the migratory range of many, many species.”

The morning after her visit to the limnocorrals, Morrissey rose at dawn to begin banding Tree Swallows at yet another site. Delighted by the diversity of ducks on every pond, she ticked off the species: Northern Shoveler and Pintail, Redhead, Canvasback—the list went on and on. “They’re on even the rubbish little potholes,” she said. “That’s what we’re interested in, collectively. Every pond is being used by ducks, songbirds, and swallows, and those ponds are teeming with invertebrates.”

The smaller potholes are the first to melt in the spring and provide food for birds, Morrissey observed. “They’re also the most susceptible to neonic contamination because they are in the middle of farm fields or they are fed by water from those fields.” But despite the ponds’ importance for flood control, irrigation, and groundwater replenishment, Morrissey said, farmers continue to fill them in. The puddles, then, are a microcosm of the two leading drivers of grassland and aerial-insectivorous bird declines: the widespread use of pesticides and habitat destruction.

Morrissey trapped and measured birds until dinnertime, then started the long drive home. “I am not saying that neonics are the only cause of bird declines,” she said. “The problem is the way we do agriculture. These pesticides are the antithesis of ecological principles.” And then Morrissey proceeded to outline an agro- ecological paradigm shift that optimizes biodiversity, limits tillage, and deploys synthetic chemicals only as a last resort—the opposite of the seed-treatment strategy.

Throughout her career, Morrissey has wallowed in details, painstakingly parsing the myriad impacts of chemicals on birds and other creatures. Now, however, she is starting to pull back and address systemic issues. “For the last 40, 50 years, farmers have listened to what chemical and seed companies tell them, instead of being self-sufficient and figuring out what their soil needs,” she said. “We can’t continue down this road: I don’t want to replace chemical A with chemical B. I think we should do ag better.” To help achieve that, she is currently designing a research program that will test multiple approaches to cutting on-farm use of synthetic chemicals. If agricultural intensification correlates with avian declines, as many studies indicate, could a reversal increase bird populations while continuing to produce enough food?

The truck flew past squadrons of wigeons, teals, Gadwalls, and grebes. “I’m concerned that the ag system will collapse,” Morrissey said, suddenly sounding weary. “We’re on a thin line with climate change, with soil health. We don’t have enough land to keep expanding out.”

She paused, then returned to the animals that had so fatefully captured her imagination on those early field trips. “Industrial farming does not support birdlife,” she said. “If we don’t have insects, we don’t have birds. It’s as simple as that.”