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Storks are gaining weight from a diet of literal junk, according to research that suggests the previously disappearing birds face potential health risks as a result of increasingly eating from rubbish dumps.
Landfill offers what appear to be quick and convenient meals for white stork populations in Europe. But new research suggests they may be gaining a short-term energy boost at the cost of hidden long-term health effects.
It points to a complicated trade-off: landfill food may help the once endangered species grow and save energy, helping to increase their population, but it may also be altering their bodies in ways that are only just beginning to be understood.
Once known for long-distance migrations between Europe and Africa, some populations have altered their behaviour as discarded food has become easier to find than natural prey.
Storks foraging from landfill can pick through human food waste, meat scraps, insects, rodents and earthworms, while spending less energy searching across fields and wetlands. But the same sites can expose birds to plastics, wires, glass and heavy metals, raising questions over whether this “junk food” diet is helping or harming them.
Anustup Bandyopadhyay, a PhD student at the University of Veterinary Medicine Vienna who was involved in the study, said growing global waste production was creating new feeding opportunities for wildlife, but the consequences for storks remained contested.
The researchers investigated white stork populations in Poland, where the birds have begun eating more from landfill over the past decade. Unlike some western European populations, most of these birds still rely mainly on natural prey, giving researchers a chance to compare individual white storks using different foraging strategies.
Their early findings, presented at the Society for Experimental Biology conference in Florence, suggested that landfill-feeding storks tend to have greater body mass and higher energy stores than those feeding naturally.
“They can spend less time foraging and potentially channel that time and energy into other activities such as breeding,” said Bandyopadhyay. “Our partners from Poland have also found that white storks use landfills mostly in the middle of the breeding season, when the food demands of nestlings are at its peak.”
But these benefits come with risks. Researchers also detected evidence of DNA damage linked to landfill diets much earlier than expected in young birds – when chicks were “only about a week old”.
The findings also suggest that the convenience and reliance on landfill foraging as a food source may influence migration patterns, as it did for white stork populations in western Europe. Bandyopadhyay said: “The Iberian peninsula white storks have shifted from being wholly migratory to partially migratory, or even sedentary, largely due to favourable weather conditions and, importantly, the availability of landfill food subsidies.”
Prof Aldina Franco, an ecologist at the University of East Anglia (UEA), who was not involved in the research, said the study broke new ground by looking at the effect of contaminants on the storks.
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Food found in landfill is like “junk food” for birds, she said. “It’s food that is rotting and it’s poor quality, and probably highly energetic. So, they can get leftover steaks or leftover fish, everything we throw away to landfill sites.”
Franco added that the picture is nuanced: “It is true that it can be damaging for individual storks to eat these types of food that can have contaminants and diseases. But from a population perspective, if you’d have ۵۰۰ storks going to a landfill site, maybe a few will die from eating these contaminated items, but the majority will actually benefit from having extra food.”
The issue is becoming more urgent as open landfill access falls in Europe because of changes to EU waste management policies. This could affect the numbers, movements and breeding success of storks that rely on them as food sources.
Franco said this could be a potential concern for the white storks populations that have become accustomed to landfill foraging.
“On the one hand we are very happy to provide food in our gardens through bird feeders. The landfill sites are waste that we don’t use and the question is, shouldn’t we allow some species to benefit from these resources that we no longer need? The white stork populations were declining until the ۱۹۸۰s. They disappeared from several European countries and now they have been reintroduced in Sweden, and in the UK just recently.”
France added: “Will the stork populations decline if we completely prevent them from accessing our organic waste? I think that’s a risk and it needs to be thought through.”
