Instead of migrating to Africa, storks are spending their winters feeding at landfills in Spain and Portugal. Storks across Europe are staying put due to availability of food waste at dumps - which causes some problems.
Junk food and sedentary lifestyle are not exclusive to humans - white storks are staying in Europe over winter, and getting addicted to food from landfills.
Waste food made available at garbage dumps throughout the year has changed storks' migration patterns; they're now staying in southern Europe instead of crossing the Strait of Gibraltar to Africa.
But the birds' behavior change hasn't always gone over well with neighbors, and efforts of European legislations to close landfills may hinder access to the storks' daily dose of trash.
But what caused these changes? And what will now happen to these junk food junkies?
No reason to move
In past years, around the beginning of February, white storks would arrive in Spain, Portugal and other European countries to breed. In autumn, ahead of the arrival of winter, they embark in a long journey of about 2,000 kilometers back to sub-Saharan Africa, were food resources are abundant.
But this traditional migratory pattern has changed due to increased availability of food in European countries. "Now 80 percent of the adult white storks breeding in Spain stay during winter," Ana Bermejo, coordinator of SEO/BirdLife monitoring program, told DW.
Foraging on organic waste in landfill sites, as well as on an invasive species of red crab introduced to rice fields, allows white storks to survive in Spain and Portugal over winter - once they've learned they can do this.
"Young storks are still migrating, probably due to their genetic information," Bermejo said. "But they learn over the years, and adapt quickly - while only 20 percent of young storks stay, now 80 percent of adults do."
Changes across Europe
Relatives to the Spanish and Portuguese storks, breeding in central and northern European countries, have also adapted their migratory behavior, and are staying in southern European countries instead of crossing to Africa.
"An increasing number of storks in Germany don't migrate anymore to Africa, and instead stay in Spain or Portugal," Holger Schulz, a wildlife consultant with Stork Switzerland, told DW.
The Swiss non-governmental organization has been tracking white storks' migratory journey for more than 10 years.
The results are clear: stork populations from countries including Germany, the Netherlands, Switzerland or France are joining the Spanish and Portuguese birds in their adventure - to the landfills.
This, however, seems to apply to storks that have historically taken the western migratory route, and not the eastern one that heads across Turkey and through the Levant to North Africa.
Happy couch potatoes and junk food junkies
Most of the white storks overwintering in Spain and Portugal congregate near landfill sites, which is the source of nearly 70 percent of the animals' diet, according to a a recent study.
During breeding season, white storks still stay close to their nests - but as the winter arrives, the daily excursions to landfills become more constant. Researchers believe white storks are getting addicted to "junk food."
"New colonies are even getting established near the landfill sites," Aldina Franco, lead researcher of the study, told DW. "Others fly almost 50 kilometers to visit the sites during non-breeding season."
And for now, it seems that white storks are benefitting from this new behavior. "Becoming resident birds, white storks keep the same nest throughout the year," Franco said. "So they have an advantage when the breeding season arrives."
"And, at least someone is eating our wasted food," Franco quipped.
Unwelcome white storks
Bermejo believes the increase of the resident stork population does not have a negative effect in the region. But he also explained that the location of storks' nests in fragile or protected buildings is an ongoing issue.
And not everyone is happy about the storks' extended stays. Some telecommunication companies, heritage conservation groups and private citizens have been working with Stork Stop - a private Spanish company aimed at controlling the birds' presence in Spain and Portugal.
"The problem is increasing at alarming rates," Eduardo Burgaleta, director of Stork Stop, told DW. "White storks develop very fast, they have no predators and are moreover protected."
The birds directly damage buildings and telecommunications infrastructure, and the increasing population with endless access to food on landfills represents a major risk, Burgaleta explained.
Using legally sanctioned methods, Stork Stop has a variety of techniques to prevent birds from nesting in places where they are not wanted.
Back to Africa?
In July 2014, the European Commission adopted a legislative proposal that would drastically reduce landfills across Europe, by more efficiently processing waste.
This would likely impact the new behavior of white storks, and the consequences are still uncertain: they may die of starvation, find an alternative source of food, or go back to migrating.
A dump site in Gibraltar has put storks in a similar situation, preventing access to food. The group Stork Switzerland is currently researching how this has affected the animals and their feeding patterns. For now, the birds have abandoned their daily visit to the site, Holger Schulz explained.
Ana Bermejo was optimistic: "White storks will probably adapt again to new conditions provided by humans."
"It is a very flexible species."