(Beyond Pesticides, November 15, 2017) Songbirds exposed to widely used insecticides fail to properly orient themselves for migration, according to a study published by Canadian scientists in Scientific Reports. With the organophosphate chlorpyrifos and the neonicotinoid imidacloprid applied to millions of acres of farmland throughout North America, this new research adds weight to arguments that pesticides are a likely cause in the decline of migratory bird populations. “Studies on the risks of neonicotinoids have often focused on bees that have been experiencing population declines. However, it is not just bees that are being affected by these insecticides,” said Christy Morrissey, PhD, biology professor at the University of Saskatchewan.
Researchers captured 57 white crowned sparrows in northern Canada, and held them in an outdoor pen for roughly two weeks, during which time all the birds either gained or maintained their weight. The songbirds were then split into three groups, one exposed to imidacloprid, another to chlorpyrifos, and the last untreated and acting as a control. The imidacloprid and chlorpyrifos exposed groups were each further separated by exposing a portion to the insecticide at 10% of the lethal dose that would kill 50% of a given population (LD50), and another to 25% of the LD50. According to the study, at those rates, the 10% dose was like the sparrows eating four treated canola seeds or less than a tenth of a corn seed, while the 25% dose was like the birds eating nine treated canola seeds or two tenths of a treated corn seed. Both insecticides are commonly used to treat the outside of crop seeds before planting. Over 90% of corn and canola seeds are likely to have neonicotinoids dusted onto them, despite strong evidence that it does nothing to improve yields.
Given that the exposure scenarios are similar to what these songbirds would come in contact with during the normal migration season, bird lovers are likely to find the study’s results deeply disturbing. Sparrows in the 10% imidacloprid group lost nearly a fifth of their weight within three days, while those in the 25% group lost over a quarter. Weight returned to normal within two weeks after dosing, but during that time, two birds had to be euthanized due to breathing problems, two birds were found dead, and seven developed excessive salivation and foaming at the mouth. In both the 10% and 25% chlorpyrifos-treated groups, weight decreased slightly, though there was no mortality or outward signs of acute poisoning.
Both insecticides, however, had significant effects on migration. Before insecticide exposure, all groups were able to successfully orient northward. Although, after imidacloprid treatments, both the 10% and 25% groups were unable to orient themselves, or when orienting were 75° off of north. While the imidacloprid treatment group was able to recover orientation abilities after two weeks, the chlorpyrifos exposed group did not orient after exposure and did not recover their orientation at all after two weeks.
A study published in 2013 in PLOS ONE by another group of Canadian scientists found that pesticide exposure ranked above even habitat loss when investigating the cause of songbird declines in the U.S. Coauthor of the study, Margaret End, PhD, noted that, “The effects we saw were severe enough that the birds would likely experience migratory delays or changes in their flight routes that could reduce their chance of survival, or cause a missed breeding opportunity.”
In 1962, Rachael Carson challenged society to envision a world without birdsong, “a spring without voices.” With reports of rapid, global population declines in song birds, pollinators, and the entire insect community, many concerned residents in the U.S. wonder whether we have truly made progress after public backlash removed DDT and certain other organochlorine insecticides from the market. With the range of adverse effects seen from exposure to these newer chemistries, neonicotinoids and organophosphates, the question does warrant consideration.
Consideration, but not despair. Rather than support the whack-a-mole approach that powerful chemical companies continue to foist on the public, where one chemical is replaced with another only after years of research finds it should not have been approved in the first place, consumers have the opportunity to support a different kind of agriculture. When making your decision at the grocery store, your food dollars decide whether to support a production system that relies upon incessant chemical use that causes yet still untold harm the natural world. Whenever possible, purchase organic, which never allows toxic synthetic insecticides to be used, because a silent spring is still a strong possibility.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.