By Abbas Nazil
A new study has revealed a grim and growing threat to bird populations worldwide: plastic entanglement in nests, especially caused by polypropylene baler twine used by farmers.
Researchers in southern Portugal found that white stork chicks are increasingly being strangled or injured by plastic debris incorporated into their nests—a problem mirrored across the globe and affecting many bird species.
During the 2023 breeding season, a team of ecologists led by Dr. Inês Catry of the University of Lisbon and Dr. Marta Acácio from the University of Montpellier monitored 93 white stork nests weekly.
Of the 600 nests photographed over a four-year period, a staggering 90% contained plastic, with 27% of inspected nests holding chicks entangled in it.
Most of the chicks were just two weeks old, and many suffered fatal injuries such as strangulation, limb amputation, and infections.
The primary cause was plastic baler twine used in agricultural hay bales, though other plastics like shopping bags and containers were also found.
Dr. Acácio recounted one case in which a chick was so tightly bound by plastic it was being eaten alive by maggots.
Although some chicks have been successfully rescued, the mortality rate remains high. According to the researchers, such deaths are often missed during typical nest inspections, as dead chicks can be swiftly removed by parents before scientists arrive.
The findings, published in Ecological Indicators, point to a much higher nestling entanglement rate than previously reported.
Other studies across Europe and the Americas found rates between 0.3% and 5.6%, but the weekly monitoring in Portugal revealed a 12% rate—raising alarms about overlooked casualties.
Experts emphasize that the problem extends beyond Portugal and white storks. Similar cases have been reported among ospreys in the U.S., southern caracaras in Argentina, and other species globally.
Dr. Neil James, an ecologist in Scotland and founder of birdsanddebris.com, reports that human-made debris has been found in nests of over 160 bird species—two-thirds of which are land-based.
Plastic baler twine, made from polypropylene, is accumulating at an alarming rate. As of 2019, over 80,000 tonnes were used annually across Europe.
Despite its widespread use, proper disposal and recycling systems are limited. While biodegradable alternatives exist, adoption is slow and not yet widespread.
Researchers are now calling for urgent action: declaring polypropylene twine a hazardous material, implementing large-scale removal from the landscape, and expanding collection and recycling programs.
Farmers can help reduce plastic pollution by keeping fields clear of debris, but systemic solutions are needed to address the broader environmental impact.
Without intervention, the seemingly harmless presence of plastic in bird nests could impose severe pressure on already vulnerable species, turning nesting—a symbol of life—into a site of fatal entrapment.