For some birds, feeding at waste sites seems preferable to long migrations to warmer climates, but researchers warn of risks to ecosystems and health

It ranks as one of the more uncomfortable impacts that humans have on wildlife. Massive rubbish dumps and sprawling landfills have led some birds to give up on migration. Instead of flying thousands of miles in search of food, they make the waste sites their winter feeding grounds.

Researchers in Germany used miniature GPS tags to track the migrations of 70 white storks from different sites across Europe and Asia during the first five months of their lives. While many birds travelled along well-known routes to warmer climates, others stopped short and spent the winter on landfills, feeding on food waste, and the multitudes of insects that thrive on the dumps.



White storks from Europe and Asia leave their nests between July and September on epic journeys to Africa, some travelling as far as 5,000 miles to the the south of the continent, the scientists report in the journal Science Advances. The birds conserve energy in flight by flapping their wings as little as possible, and soaring on thermal currents.



In the short-term, the birds seem to benefit from overwintering on rubbish dumps. Andrea Flack at the Max Planck Institute for Ornithology in Radolfzell found that birds following the most traditional migration routes were more likely to die than groups of German storks that flew only as far as northern Morocco, and spent the winter there on rubbish dumps.



“For the birds it is a very convenient way to get food. There are huge clusters of organic waste they can feed on,” said Flack. The meals are not particularly appetising, or even safe. Much of the waste is discarded chicken heads and rotten meat, mixed in with other human detritus such as nappies, plastic bags and old toys.



“It’s very risky. The birds can easily eat pieces of plastic or rubber bands, which can get stuck in their throats, and they can die,” said Flack. “And we don’t know about the long term consequences. They might eat something toxic and damage their health. We cannot estimate that yet.”



The scientists tracked white storks from eight different colonies, in Armenia, Greece, Poland, Russia, Spain, southwest Germany, Tunisia and Uzbekistan. The Russian, Greek and Polish storks flew as far as South Africa, while those from Spain, Tunisia and Germany flew only as far as the Sahel. Uzbek birds did not migrate at all, and all overwintered around their home grounds near Tashkent.



Landfill sites on the Iberian peninsula have long attracted local white storks, but all of the Spanish birds tagged in the study flew across the Sahara desert to the western Sahel. Writing in the journal, the scientists describe how the storks from Germany were clearly affected by the presence of waste sites, with four out of six birds that survived for at least five months overwintering on rubbish dumps in northern Morocco, instead of migrating to the Sahel.



Flack said it was too early to know whether the benefits of plentiful food outweighed the risks of scavenging on landfills. But that is not the only uncertainty. Migrating birds affect ecosystems both at home and at their winter destinations, and disrupting the traditional routes could have unexpected knock-on effects. White storks feed on locusts and other insects that can become pests if their numbers get out of hand. “They provide a useful service,” said Flack.

