For their nest building, birds use increasingly man -made materials such as plastic cords and networks, especially in urban and more dirty areas. However, the chicks can hurt or even die from the garbage. How dangerous different types of plastic waste are for the bird chicks and where the materials come from have now examined ecologists using storks in Portugal.
The pollution from plastic is a major problem: fish, turtles and other underwater dwellers get caught in plastic parts and stifling or starved in the sea because they confuse the garbage with food. But the plastic bags, cords and similar materials also pose a danger to animals on land. For example, researchers have observed how adult storks eat rubber bands and die from it – they probably thought the birds were for earthworms.
Both storks and other bird species also use plastic waste to build their nests. “The reasons for the use of these materials in the nest building are not fully clarified, but could be related to their availability and scarcity of natural materials,” explains co-author Inês Catry from the University of Lisbon. “Some materials could also incorrectly considered food and accidentally installed in the nests.”
91 percent of nests affected
A research team around Ursula Heinze from the University of East Anglia in Norwich has now examined which man -made materials and how much storks use storks and where the garbage comes from. For this purpose, the biologists photographed 568 stork nests in the south of Portugal between 2018 and 2023 and also examined chicks of 93 nests. In order to determine the origin of the unnatural nest materials, the team evaluated land use within a radius of 3.5 kilometers around the nests using a special map. Storks are looking for food on average at this distance.
The result is clear: in 91 percent of nests the ecologists found man -made material. The storks most frequently used soft plastic, for example bags, for the nest building. 65 percent of the nests contained this garbage. Furthermore, the researchers found further plastic waste, such as ropes, winding nets for hay bales, weed covers and hard plastic, as well as paper, sponges and fabrics in the children’s jet. 35 stork chicks got tangled in the garbage- 22 times in ropes, for example so-called pressing yarn, which farmers use to tie straw or hay bales. The team released the stuck chicks from the fatal trap.
“This is a serious problem,” explains co-author Aldina Franco from University XXX. “The chicks get caught in synthetic ropes at a very young age, which are slowly strangling their limbs, especially legs and feet, during their growth, which leads to necrosis and amputations. They suffer a terrible death.”
Agriculture as the main source of “nest waste”
Some nests were almost completely surrounded by agricultural areas, while others were near settlements or landfill. Heinze and her colleagues found the more plastic ropes in the nests, the more arable land and areas with combined forestry and agriculture were around the stork nests. In the examination area in Portugal, agriculture was the main source for “nest waste”. It looks similar in other countries.
“Our study comes at the right time, because it illuminates a widespread problem with barely quantifiable consequences,” says Franco. “In Great Britain, several sparrow birds, such as rigid litters and the fare, also started to use different colored polypropylene threads for nesting. And in Ukraine, soldiers can find nests with fiber optic cables from remote -controlled drones,” continued Franco. The operator controls the drones using fiber optic cables so that they cannot be influenced by cyber attacks or interference. These cables are usually ten kilometers long and not biodegradable.
But what can be done against this pollution? While determined disposable plastic is prohibited in the EU, Canada and some East African states, press yarns are still allowed in agriculture. In view of their observations, the ecologists recommend that you no longer use press yarn and instead to use Sisal for the tying of straw and hay bales and to remove the remains of the yarn from the environment.
Source: Ursula Heinze (University of East Anglia) et al.; Ecological Indicators, DOI: 10.1016/J.ecolind.2025.113796
