Hundreds of storks are getting hooked on a ‘trash diet’ in Spain, sticking near landfill sites instead of flying south to Africa.

As with so many upsets to the natural world, climate change and pollution are to blame. Higher temperatures make the long journey to the Sahel region less appealing, while garbage pits seem to cater to the birds’ needs.

But Madrid’s Colmenar Viejo landfill – replenished by 100 truckloads of household waste a day – is a poor and dangerous substitute.

Why???

“Every year chicks and adults die because they ingest plastics or rubber that they think are worms,” says Blas Molina, an ornithologist working with Spanish bird charity SEO/Birdlife.

“In many cases, their legs get tangled in plastic cords cutting off their blood supply, and they die from that eventually.”

A census in Autumn 2020 found 36,217 of Europe’s approximately 450,000 white storks in Spain. Together with Poland, it is the most popular host country for the breed in Europe. In the Madrid area alone, researchers recently counted 2,300 breeding pairs of birds, compared with just 200 registered in 1984.

And with temperatures in the capital on track to jump 3.1C by 2050, more and more storks will be drawn to Madrid in winter. There are significant consequences for both birds and humans.

Near the Colmenar Viejo landfill, hundreds of white storks have built nests up to six feet long on roofs and in the bell tower of the nearby church. There are even nests on street lights.

“This is a stork paradise because they have grass, pastures and then the landfill, so they have it all here,” says Alejandro López García, who is studying Madrid’s stork population for his PhD at the city’s Complutense University.

There is also a clear trend for storks to build nests away from traditional wetlands to urban-adjacent areas. These large birds are fiercely loyal to their nesting sites and will return to them year after year, concentrating their populations around landfills across Spain.

Increasingly, humans and storks are living alongside each other, in a sometimes awkward compromise. White storks can boast a wingspan of up to seven feet, and weigh up to 10 pounds, so require ample space to nest.

Now that the storks have altered their migration and breeding patterns to adapt to the plentiful garbage piles on offer, a new threat looms.

In 2020, Spain adopted into national law a European Union directive that aims to stop all organic waste ending up in landfills.

“This means that the food they are eating right now would cease to exist,” López García says, suggesting that an area for storks to feed should be maintained at the garbage dumps. “What we’re proposing is that there’s a smooth transition that doesn’t happen overnight.

But in the final analysis, reducing planet-warming methane by cutting organic material in dump sites definitely outweighs the benefit of the food source that the storks can find here. “In the medium-to-long term, the feeding from landfills is negative for them,” he says.

The negative effects of the storks’ garbage diet also reach human populations.

Storks from across Europe will still make a short hop southwards during the winter, but if they are feeding at trash sites then potentially toxic chemicals can be transferred to the reservoirs and drinking water sources they stop at along the way.

“All the pollutants that you have here, or potentially toxic compounds, end up in those waters,” López García explains.