In Europe, legend has it that white storks, those long-distance migrants, deliver babies. Turns out, that’s not true—and not just the part about the babies (The origin of the myth? Since white storks' migration lasts for nine months over the fall and spring, legend has it that they'd return with babies after the nine month migratory and gestational cycles). Large numbers of the birds are sticking closer to their breeding grounds thanks to a plentiful food supply in the form of heaps of garbage.
White storks typically breed in Northern Europe and winter in Africa. Since the 1980s, however, the birds have increasingly opted to winter in Spain and Portugal instead.
“These birds have changed their behavior very radically,” Alidina Franco from the University of East Anglia told Science Daily. “The number of storks spending their winter in Portugal has increased hugely from around 1,180 birds in 1995 to more than 10,000 in 2008 and numbers continue to grow.” Like this growing population, BirdLife reports that their entire European population is generally healthy and increasing, with their last population estimate in 1994 revealing 180,000 breeding pairs.
In Spain and Portugal, massive collections of trash and food waste are uncovered, providing a feast for storks and negating the need for them to fly to Africa for sustenance in winter.
Climate change is, of course, another suspected culprit in the birds’ changing migration patterns. With warmer temperatures they’re breeding farther to the north, according to Science Daily, and don’t need to travel as far for the winter.
To better understand why the birds’ behavior is changing, researchers at the University of East Anglia will track 15 adult storks with GPS loggers for a year. The devices will record the storks’ positions five times a day and reveal when the birds keep their heads down at the location of a waste pile—an indication that they’re foraging on that food source. Their diet is vast and opportunistic, dining on small mammals, insects, amphibians, and crustaceans when they don’t have the opportunity to pick at a food mound.
More so, project lead Franco and her PhD student Nathalie Gilbert hope to gain a better understanding of the connection of climate change and trash piles on these birds, determining whether it is warmer temperatures or the availability of trash piles that’s causing storks to use more northern winter and breeding sites.
Portugal plans to gradually move its trash piles indoors, so understanding this relationship will be crucial as the storks are forced to seek out alternative food sources in the future.
For now, though, the storks will continue dirtying their white plumage amid piles of food scraps.