The white storks in Portugal and Spain have become addicted to junk food at landfills. So much so that they have started skipping their annual winter migration to Africa, according to a new study published Wednesday in the journal Movement Ecology. Aldina Franco, lead author and a conservation ecologist at the University of East Anglia, said the big birds’ staycation slowly began in the 1980s.

European Storks Skipping Annual Migration To Live On Landfill

14,000 resident storks in Portugal

Before the 1980s, these birds were wholly migratory. The first individuals started staying in the 1980s, and now the numbers have increased exponentially. Franco said there were only 1,187 resident storks in Portugal in 1995. The number has today reached 14,000. Researchers found that 80% of white storks that have skipped winter migration congregate near landfills.

They cherish junk food on landfill sites, mainly during the non-breeding season when other food sources are scarce. The landfill sites have enabled all year-round nest use, a behavior that was developed only recently. Having a nest near a guaranteed food supply is very important. So storks spend their non-breeding season to defend their desirable nests. Even those living as far as 30 miles fly to landfills for a feast.

Human activity responsible for these changes?

The stay-at-home birds also have an advantage over their migrating counterparts. It allows resident storks to select the best nest sites and start breeding when mating season begins. These are not the only birds giving up their migratory ways. Birds such as North America’s Canada goose and turkey vulture have showed similar patterns in the past.

Researchers said it was difficult to say whether such changes in migration are occurring more frequently due to human activity. Climate change has led to milder winters in the region, making life easier for storks in Spain and Portugal. But the party isn’t going to last long because the European Union has decided to close landfills with open air trash piles by 2018, said Franco.