Reductions in pollinator populations — such as bees and butterflies — have been widely reported. Last year, a German study showing a staggering 76 percent decrease in flying insects had many experts buzzing about an “ecological Armageddon.”
Now, a pair of French studies show that avian population numbers are also plunging. The studies — one focused nationally and one on a specific agricultural region — found a sharp slide in the number of farmland birds, such as skylarks and linnets, and has researchers sounding further alarms.
While loss of habitat, changing climate, and wind turbines all affect bird populations, pesticides are also likely contributors to the decline, the researchers say. Since most avian species rely on insects for part of their diet, the substantial decline in insect numbers due to pesticide exposure has played a key role in the loss of bird biodiversity, too.
“Even granivorous birds feed their chicks insects, and birds of prey eat birds that eat insects,” explains Benoit Fontaine, PhD, of France’s National Museum of Natural History, in the Guardian. “If you lose 80 percent of what you eat, you cannot sustain a stable population.”
The studies noted that a third of the bird population has disappeared over the past 17 years. Certain species fared much worse. For example, seven out of 10 meadow pipits and eight out of 10 partridges vanished during the respective study periods.
“We’ve lost a quarter of skylarks in 15 years. It’s huge, it’s really, really huge,” adds Fontaine, who coauthored one of the studies. “If this was the human population, it would be a major thing.”
The dramatic reduction in French bird populations is reflected across Europe. According to the European Bird Census Council, farmland bird numbers have fallen by 55 percent since 1980.
Bird numbers have been steadily declining in North America as well. According to Partners in Flight, 22 of their 86 Watch List species have lost at least half of their population in the past 40 years and are projected to lose an additional 50 percent of their current population within the next 40 years.
Degradation of grasslands and forests plays a role, but pesticides may also be a factor in avian decline in North America. A 2017 University of Saskatchewan study published in Scientific Reports found that insecticides had a substantial impact on migrating, seed-eating passerines, or perching birds.
During a spring migration, for example, researchers captured sparrows and fed them seeds coated in low or high doses of a common insecticide — either the neonicotinoid imidacloprid or the organophosphate chlorpyrifos — for three days.
The songbirds lost up to 25 percent of their fat stores and body mass — as well as their sense of direction — all of which are crucial for migration.
Since migratory songbirds use farmlands as stopover points during long flights, researchers say they’re likely to encounter these neurotoxic insecticides during their journeys.
“We were encouraged that most birds survived, and could recover following the cessation of dosing,” said postdoctoral fellow Margaret Eng. “But 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.”
Imidacloprid and chlorpyrifos use is highly controversial because of its potential environmental and human impacts. An imidacloprid ban is being considered in Canada.
In the United States, the Trump administration requested a delay in determining whether three widely used organophosphate pesticides — chlorpyrifos, diazinon, and malathion —are harmful to 1,800 threatened and endangered species, based on requests from pesticide manufacturers who question the governmental research conducted under the Obama administration.
Organophosphorus gas was developed as a chemical weapon before World War II, and chlorpyrifos has been in use since the 1960s as a pesticide on corn, soybeans, fruit and nut trees, cranberries, and a range of row crops, as well as in roach and ant bait stations often used in homes.
If you’re looking for something proactive, here are 10 ways you can help birds.