White storks give up migration for rubbish tip 'junk food', study finds


Storks have long brought babies to new parents in folklore but now it seems the birds are more likely to be taking "junk food" from landfill sites.

White storks are giving up on their winter migration from Europe to Africa in favour of staying near rubbish tips all year round, where they are provided with a steady source of waste food and can boost their breeding chances, research shows.

Some birds have even been tracked making round trips of up to 60 miles to get their junk food fix, a study led by scientists at the University of East Anglia (UEA) has found.

European Union rules demanding a shift from open landfill to covered sites that are inaccessible to birds could hit populations of white storks, according to the researchers, whose findings are published in the journal Movement Ecology. 

Since the 1980s, increasing numbers of white storks no longer migrate to Africa, choosing to stay all winter in Spain and Portugal, which now has about 14,000 wintering storks.

Cutting out the winter migration means birds do not have to expend energy, can secure the best nesting sites and breed earlier, with bigger broods and a better survival rate for their chicks, but the trade-off is they are likely to struggle to find food in winter.

However, landfill sites provide reliable food supplies in one place all year, which allows the birds that stay near them to remain on their nests through the winter, the study said.

The research team tracked 48 birds with GPS tags which transmitted their positions five times a day and collected data about their activities.

A large percentage of the GPS positions were recorded on the nest outside of the breeding season for the majority of the tagged storks, confirming they were using their nests all year.

Storks nesting close to landfill sites used them more and had smaller ranges for foraging for food in other habitat, showing they had a higher reliance on the rubbish tips, the researchers said.

Storks also travelled as much as 48.2km (30 miles) to visit landfill sites to forage for food outside the breeding season and up to 28.1km (17.5 miles) during breeding - much further than previously estimated, the study said.

Lead researcher Dr Aldina Franco, from UEA's School of Environmental Sciences, said: "We found that the landfill sites enable year-round nest use, which is an entirely new behaviour that has developed very recently.

"This strategy enables the resident birds to select the best nest sites and to start breeding earlier.

"Having a nest close to a guaranteed food supply also means that the storks are less inclined to leave for the winter. They instead spend their non-breeding season defending their highly-desirable nest locations."

A shift to new facilities handling food waste under cover "will cause a problem for the storks as they will have to find an alternative winter food supply", and could affect the birds' distribution, breeding and decisions on migration, she said.