White-crowned sparrow with a transmitter fixed to its back. Photo: Margaret Eng, www.cbc.ca
You’d have to have been well isolated from the world for the last few years not to have heard about the controversy over neonictinoid pesticides (usually called neonics) and their effect on pollinators, especially honeybees. But a recently published study shows the damage may extend to songbirds as well.
How Neonics Are Used
Typically, crop seeds (corn, soybeans, canola, etc.) are coated with a neonic like Imidacloprid before sowing. The seedlings absorb the pesticide (it’s systemic) and diffuse it through the crop, protecting it from future pests like flea beetles and caterpillars.
Birds and Neonics
This technique has long been considered to harm birds indirectly by killing off their prey insects, but this study shows they may be poisoning the birds themselves.
Even in the best of cases, not all the seeds in a farm field are covered in soil after sowing, and seed-eating birds ingest the exposed ones. This study suggests that this can have a harmful effect on their reproduction.
White-crowned sparrows (Zonotrichia leucophrys), small songbirds that winter in the southern U.S., but nest in the boreal forests of the north, were tested during their migration to their summer territory. As they travel, they fatten up on seeds and that can include ones treated with neonics.
The study involved feeding trapped birds three different levels of imidacloprid*-laced oil: a low dose, a higher dose and a control group that received only oil. They were then released and followed using a transmitter. The result was rapid weight loss in birds having absorbed the pesticide and a resulting delay in continuing their northward migration (the average was 3.5 days for the sparrows exposed to the highest dose) as they recuperate.
*The most commonly used neonictinoid insecticide.
Not only does this prolonged stopover leaves them vulnerable to predators, but, researcher Margaret Eng of the University of Saskatchewan believes it goes further than that. Basing this idea on previous research, she suspects their later arrival at their nesting grounds means they often find their territories taken. And they will likely also miss the peak period of food availability, vital in raising their young. As a result, if indeed they do succeed in nesting, they’re likely produce fewer eggs and fewer young may survive to adulthood.
This seems to confirm another study that found birds living near treated fields delayed egg-laying and had chicks that weren’t as healthy.
In Your Garden
Home gardeners hoping to attract birds to their gardens aren’t likely to be using neonics themselves (few are available for use as domestic pesticides), but their farmer friends may well be, at least in North America (in Europe, they’ve been largely banned), so don’t be afraid to express your concerns to your government representative.