Seagulls transport 400 kilos of plastic a year in their crops to a lagoon where thousands of flamingos breed

In the Fuente de Piedra lagoon (Málaga), where thousands of flamingos breed, an average of 400 kilos of plastic are deposited every winter.

They are carried in their crops by black-backed gulls (

Larus fuscus

) that feed in the surrounding landfills, indicates a study by the Higher Council for Scientific Research (CSIC).

Researchers have followed 45 specimens for 10 years and have analyzed feces and pellets - balls of undigested food that birds regurgitate - in this saltwater lagoon, the largest in Andalusia and the second largest in the interior of the Iberian Peninsula. .

“You can find anything from the remains of a toy stroller, to parts of baby bottles, bottles, caps, bags, elastic bands, masks, ropes or glass, among others,” describes Víctor Martínez, lead author of the study and researcher at the Institute of Sciences. del Mar (ICM-CSIC).

The main material located is polyethylene (54%), a component of packaging and bags, followed much further by polypropylene (11.5%) and polystyrene (11.5%).

To determine how much and what plastic these accidental winged transporters carry, they combined their movement patterns with bird counts at Fuente de Piedra and dietary studies of the remains regurgitated by groups of up to 20,000 gulls that winter there.

“86% of the ejected balls contained plastic and 96% other debris such as glass and textiles,” the scientists indicate.

Only 1% was detected in excrement.

The black-backed gull is abundant in the lagoon's nature reserve, about 1,475 hectares long, where the species spends the winter after traveling from the United Kingdom, the Netherlands and Belgium, places where it breeds.

Their number has been increasing since the landfills were built, scientists say.

In these facilities they easily locate organic waste to feed on, which is mixed with plastic remains.

Some travel up to 80 kilometers (round trip) to the garbage treatment center in the city of Córdoba.

“Although, normally, they visit other closer ones like Antequera or Montalbán,” says Martínez.

They also feed in the crop fields surrounding the lagoon where olive trees abound.

“If we managed to reduce the amount of plastic we generate and improve its separation from the organic part of the garbage, less would end up in landfills and intake would be reduced, because although these facilities keep more and more remains in hangars, seagulls enter through the door,” adds the scientist.

Furthermore, it is a very intelligent animal, which immediately detects risks.

“You start capturing them in a landfill and the next day they are gone, they knew us, they had us registered,” he describes.

Ingesting plastics is harmful to birds and can even be fatal, but this study shows that it can also cause problems in natural ecosystems, which birds use as resting or breeding areas.

Andy Green, co-author of the document and researcher at the Doñana Biological Station, indicates that “this is, by far, the main source of plastics entering Fuente de Piedra, materials that end up decomposing into smaller particles.”

And it is likely that they remain in the lagoon because there is no drainage as it is endorheic and it empties with evaporation.

“They stay there converted into microplastics and in the end they end up in the fauna of the lagoon, also in the flamingos,” says Green.

Fuente la Piedra is one of the most important flamingo breeding areas, although the lack of water caused them to be passed by last year.

However, the previous year in June there were 17,000 birds raising their chicks.

“They need between three and four centimeters and I don't know if it will be achieved this year,” explains Felipe Álvarez, from SEO/BirdLife.

In addition to this species, the lagoon is a refuge for cranes, ducks and endangered species such as the white-headed duck, the brown pochard and the gray teal.

It is not only the case with seagulls, there are other opportunistic birds such as the white stork (

Ciconia ciconia

) that also look for food in landfills.

A study evaluated specimens of this species that used the waste complex of the Bay of Cádiz.

On average, they counted 599 storks per day moving between the landfill and a complex of salt ponds and marshes where they regurgitated pellets containing an average of 0.47 grams of plastic waste, most of it polyethylene.

The models used led scientists to estimate that 99 kilos and more than two million plastic particles were moved to the wetland.

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