Landfills Have Become Giant Bird Feeders for Europe’s White Storks
For Europe’s white storks, landfills have become an all-you-can-eat buffet.
It’s such a tempting supply of ready—if somewhat disgusting—food that some of the storks have stopped migrating. Instead of making their annual journey thousands of miles south to wintering grounds in Africa, the birds are instead opting to stick around the landfills year-round.
Not only that, but the juvenile birds that spend their time in the landfills have a greater survival rate than the birds that fly south for the winter, according to a study published Friday in the journal Science Advances.
The survival rate may have something to do with the amount of energy it costs the birds to hunt for food. “Birds on garbage dumps did not really have to search for their food, and on first sight it seems very beneficial for them to feed on the garbage dumps,” said Andrea Flack, a postdoctoral researcher at the Max Planck Institute for Ornithology and the lead author of the study.
Flack and her coauthors studied white storks from eight countries. They attached GPS transmitters to learn where they flew during the first five months of their migration, a period that many juvenile birds don’t survive even under the best of conditions. They also used accelerometers to track the birds’ speed, allowing the researchers to estimate how much energy the birds used while flying.
The results were striking. The birds that live in Poland, Russia, Greece, and Tunisia didn’t spend much time at landfills and subsequently flew more than 10,250 miles—journeys that required a tremendous amount of energy. Perhaps because of this energy expenditure, the death rate for the young birds was as high as 80 percent.
Other birds fared better. The population of birds in Uzbekistan that never traveled more than 100 miles from their home landfills had a 50 percent survival rate.
Exactly what’s on the storks’ landfill menu isn’t clear, but Flack said it’s probably a combination of waste food that humans have dumped and small rodents and insects that feed on the garbage.
Beyond landfills, the birds that migrated encountered a wide range of human-influenced environments that also affected how far they traveled. The birds that flew farther south—sometimes all the way to South Africa—passed over large uninhabited areas with good supplies of vegetation and food. The birds that stopped north of the Sahara encountered denser human populations and as a result had to conserve more of their energy while they flew. “It surprised us that those storks that did not cross the Sahara were able to reduce their movement energy so drastically compared to those birds that overwintered in the south of Africa,” Flack said.
The study leaves several unanswered questions. For one thing, could the landfill-dependent birds suffer from their less-than-healthy diet? “We don’t really know whether there are negative long-term consequences of these garbage diets, but it is certainly possible,” Flack said. She added that researchers know the storks eat plastic tubes, garbage bags, and other objects that get stuck in their throat or fill their stomach.
Perhaps more important, is the broader ecosystem suffering because the birds are no longer migrating? What happens to areas where the storks used to winter if they no longer come there every year? “Storks feed, for example, on insects or small reptiles,” Flack said. “They might help with pest control by feeding on locust swarms” or other species that could grow uncontrolled in the storks’ absence.
Figuring out that piece of the puzzle could be important not just for the birds but for the planet. As the authors conclude in their paper, “Understanding how human actions alter migratory patterns may be the key not only to protecting migratory species but also to maintaining diverse and stable ecosystems.”