In Portugal, storks, the birds known in folklore for dutifully delivering babies, have become homebodies.

The reason, according to a study published Tuesday in the journal Movement Ecology, is the tasty local landfills in the south-central part of the country. Thousands of birds have chosen to forgo their typical winter migration to sub-Saharan Africa in favor of sticking around to gorge on garbage.

“Before the ’80s there were no storks in the Iberian Peninsula in Europe during the winter,” said Aldina Franco, a conservation ecologist from the University of East Anglia in England and a co-author of the paper. “Suddenly we saw a few birds and then the number increased and now we have 14,000 birds in Portugal in the winter.”

Previous studies showed that the birds made pit stops at landfills while migrating south. But this was the first study to confirm that some storks, enticed by the year-round buffet, are taking up permanent Portuguese residency.