17
Sep
Study Finds Neonics Result in the Silent Demise of Songbirds
(Beyond Pesticides, September 17, 2019) The poisonous farm fields migratory birds forage on during their journey reduce their weight, delay their travel, and ultimately jeopardize their survival, according to new research published in the journal Science. Like their effects on pollinator populations, neonicotinoid insecticides generally are not killing migratory songbirds outright, but instead precipitating a cascade of sublethal impacts that reduces their fitness in the wild. As the authors told Environmental Health News, the study is a call not simply to ban neonics or one class of chemical, but to change the entire farming system toward more sustainable bird and bee-friendly practices.
Using new technology, this study was not only able to dose wild-caught songbirds (white-crowned sparrows), but also track their migration route using automated telemetry. Apart from the control group that received no pesticide exposure, sparrows were treated at levels well below the median lethal dose (3% of the lethal dose in the ‘low’ exposure group and 10% within the ‘high’ exposure group), and permitted to continue on their migratory path. These are exposure amounts similar to a songbird accidentally ingesting a few treated seeds, according to the study.
Within six hours, both the ‘low’ and ‘high’ exposure group showed a significant reduction in body mass (3% and 6%, respectively) after a single dose of the neonicotinoid imidacloprid. The ‘low’ exposure group ate 8% less than the control group after dosing, while the ‘high’ exposure group reduced its intake by a staggering 70%. This is an important impact because body weight and fat storage are critical during songbird migration. Birds rest at stopover sites to refuel, and return to flight, but birds in the experiment dosed with imidacloprid stayed on average 3.5 days longer than the unexposed control group. Authors suspect that this was the result of weight reduction and reduced feeding.
“Extended stopovers while intoxicated and in reduced body condition could lower survival by increasing susceptibility to predation or inclement weather,” the study indicates. In addition, “Birds that are delayed during migration and arrive later at breeding grounds have been reported to obtain poorer-quality territories, breed later, and produce fewer offspring in worse condition than those of early arrivals, reducing the probability of their offspring recruitment to the population.”
Neonicotinoids are in use throughout the migratory path of these songbirds, indicating a risk that accumulates over time, given that avoidance of treated seeds appears to be a learned, rather than innate bird behavior.
Indeed, there is prior evidence that birds are already feeling the effects of neonicotoinoid use. A 2017 study by the same set of researchers found similar impacts on songbird weight and effects on migration orientation. Research conducted by Canadian scientists in 2018 found turkeys that feed on agricultural fields to be widely contaminated with neonicotinoids, indicating a potential link between exposure and poor reproductive output noted by hunters in the region. Studies from Spanish researchers (1, and 2) also indicate partridges exposed to neonic-treated seeds can reduce fecundity and impact the health of their offspring.
Risks to songbirds are also not limited to agricultural settings. In a report published earlier this year by California’s Department of Fish and Wildlife, a soil drench application of the neonicotinoid imidacloprid was implicated as causing a die-off of goldfinches in the area.
Ultimately, the authors indicate that although neonics are of particular concern, simply eliminating their use will not address the problems being observed. As co-author Christy Morrissey, PhD, told Environmental Health News, there are “already replacement for neonics—and they’re just as toxic as neonics, they’re just a different name.” To fix the problem focus should be on the “need to change the whole system to make it more resilient.”
“Monoculture, single crop agriculture is heavily reliant on chemicals for production, unfortunately, that’s just not conducive to life and biodiversity,” she told Environmental Health News. “We should incentivize farmers to diversify systems rather than substituting one chemical for another.”
Beyond Pesticides wholeheartedly agrees with Dr. Morrissey’s assessment, and has long called for a broadscale transition to organic systems. This approach focuses on soil health, and aims to work with, rather than against nature in the management of pests and weeds. Focus in placed on alleviating the root causes of pests and weeds through good nutrition, proper watering, and other cultural practices such as cover crops and crop rotation. As the success of organic farming has shown, this approach can feed the world while protecting the environment. Without this changeover the future is certain to bring more and more silent declines, building towards the Silent Spring Rachel Carson warned could occur.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Environmental Health News, Science (peer-reviewed journal)
