Before dawn in southern Spain, thousands of birds rise from rubbish tips and head towards some of Europe’s most treasured wetlands.
What looks like a graceful daily commute hides a grim freight: bits of packaging, plastic bags and silicone shards moved, piece by piece, from human landfills into fragile lagoons and marshes that are supposed to be protected.
Birds turning into plastic couriers
Plastic pollution does not just drift on ocean currents or blow across motorways. In Andalusia, it also travels by wing. White storks and several gull species are unintentionally hauling hundreds of kilos of waste every year from sprawling landfill sites to Ramsar-listed wetlands and nature reserves.
Researchers from Spain’s Doñana Biological Station spent years tracking this hidden traffic. They fitted birds with GPS tags, sifted through regurgitated pellets and droppings, and then scaled up their findings to the level of whole populations.
Their conclusion: birds have become biological conveyors, linking human dump sites with habitats that, on paper, enjoy international protection.
The work focused on three familiar scavengers of southern Spain’s landfills:
- Yellow-legged gulls
- Lesser black-backed gulls
- White storks
All three shuttle between rubbish dumps and wetlands on a daily or seasonal basis, depending on migration patterns and breeding cycles.
How a trip to the tip ends in a lagoon
In many parts of Andalusia, the routine is almost clockwork. Gulls and storks feed on food scraps, waste fish and organic matter at landfills. Along with that, they swallow plastic fragments, films, fibres and sometimes larger objects.
Later, when they rest in nearby wetlands, the birds rid themselves of the indigestible pieces. They do this in two main ways.
Pellets, droppings and hidden waste
Like owls, many waterbirds cough up compact pellets. These are small, compact bundles of bones, shells, seeds and anything else their digestive system cannot process. The Andalusian team kept finding plastic and even glass inside these pellets, as well as in faeces.
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Every pellet left on a shore or island can contain several plastic items, quietly adding to the contamination of the resting site.
By combining how much plastic they found per bird, how often individuals visited landfills, and how many birds were present across a whole region, the scientists could estimate how much waste was being moved each year.
Hundreds of kilos reaching protected sites
One of the best-known wetlands in southern Spain, Fuente de Piedra lagoon in Málaga province, became a focal point of the research. The site is famous for its large colony of greater flamingos and is protected under the Ramsar convention.
Fuente de Piedra is an endorheic lagoon, meaning water flows in but not out. Salts, nutrients and any pollutants that arrive stay there and become more concentrated over time.
In winter, thousands of lesser black-backed gulls that breed in northern Europe congregate on this lagoon. Many of them commute daily from landfills in Málaga, Seville and Córdoba.
The team estimates that these gulls alone are importing roughly 400 kilograms of plastic every year into this single wetland.
Another hotspot is the Bay of Cádiz Natural Park, a mosaic of saltmarshes, mudflats and channels heavily used by migratory and resident birds. Here, all three studied species share the same dumps and the same resting areas.
Across the bay’s marshes, the researchers calculated that gulls and storks together move about 530 kilograms of plastic per year. That number hides some striking differences in how each species behaves.
Storks vs gulls: different birds, different burdens
White storks are larger than gulls and produce bigger pellets. That means each individual stork can carry more plastic in one go. Yet they are less numerous than gulls at these sites.
When the numbers were added up, lesser black-backed gulls emerged as the main plastic movers in the Cadiz study area, shifting about 285 kilograms per year. Their dominance is not because they are particularly sloppy feeders, but because there are so many of them, especially in winter.
| Species | Approximate role | Estimated contribution |
|---|---|---|
| Lesser black-backed gull | Abundant winter visitor | ~285 kg per year |
| Yellow-legged gull | Resident breeder | Part of remaining ~245 kg |
| White stork | Large-bodied landfill user | Part of remaining ~245 kg |
Location also plays a central role. Birds nesting or resting closer to landfills visit them more often, then bring the waste back to nearby marshes and lagoons.
Wetlands in the shadow of a dump are far more exposed than distant sites that the same species rarely reach.
Year-round pollution for some species
The studies showed clear seasonal and spatial patterns. Yellow-legged gulls, which breed along the Andalusian coast, were found to transport plastic around their nesting colonies, and they did so throughout the year.
Lesser black-backed gulls and white storks, by contrast, moved the most plastic during migration or specific seasons when they rely heavily on landfill food. Different species also favoured different types of plastic. Storks were the only birds observed bringing back silicone fragments from dumps, for reasons that remain unclear.
Plastic risks far beyond the birds themselves
The immediate danger for birds is obvious: large pieces of plastic can tangle around legs, wings or necks. When swallowed, they can block the digestive tract, reducing appetite, causing internal injuries or even death.
The less visible threat lies in microplastics and chemical additives. Small fragments and fibres can pass through the gut wall or lodge in tissues. Many plastics contain additives that act as endocrine disruptors, interfering with hormones that regulate growth, metabolism and reproduction.
Once plastic breaks down into tiny pieces, it can move from one organism to another, climbing the food chain and concentrating at higher levels.
In wetlands, plastic particles can be eaten by invertebrates such as worms, crustaceans and insect larvae. Fish and birds then consume these invertebrates, and predators eat the fish and birds. Over time, the contaminants accumulate across multiple steps of this chain.
Why stopping birds at landfills is not straightforward
The European Union’s landfill directive (1999/31/EC) encourages sites to use deterrent measures to keep birds away. These can range from netting and wires stretched over rubbish, to loud noises, falconry, or changes in how and when waste is exposed.
Yet there is sharp debate over how far these tactics should go. Many gull and stork populations have adapted to landfills as a major food source. Sudden exclusion can affect their survival and breeding success, potentially pushing them to scavenge in other, less controlled places such as small illegal dumps or city streets.
Managers also face a practical dilemma. Some deterrents displace birds only a short distance, which may simply shift the plastic transfer to another wetland used as a roost.
The part humans can actually control
Researchers stress that the birds are not villains here; they are symptoms of a wider waste problem. Landfills stuffed with lightweight packaging create irresistible feeding grounds for opportunistic species.
Reducing the amount of plastic reaching these sites cuts the problem at its source. Three everyday habits still make a real difference:
- Reduce: avoid unnecessary packaging and single-use plastics.
- Reuse: choose durable containers, bags and bottles, and keep them in circulation.
- Recycle: sort waste correctly so less ends up buried in landfill cells.
Better landfill design also matters. Covering waste quickly, capturing wind-blown litter, and separating organic fractions from mixed plastic-rich rubbish can limit what birds access. Some sites are testing enclosed tipping areas or mechanical pre-treatment that shreds and compacts waste before birds can reach it.
What terms like “Ramsar” and “endorheic” really mean
Several technical words crop up in this research. Two of them affect how worried we should be about these wetlands.
“Ramsar site” refers to a wetland listed under an international treaty signed in the Iranian city of Ramsar in 1971. Countries commit to protect these areas because of their global importance for biodiversity, especially waterbirds. When birds bring plastic into a Ramsar site, the pollution problem gains an international dimension.
An “endorheic” lagoon such as Fuente de Piedra has no natural outlet. Water leaves only by evaporation or seeping into the ground. Any dissolved salts, nutrients or pollutants brought in by streams or animals tend to stay and build up. In this kind of basin, every kilo of plastic that arrives has a long residence time.
What might happen if landfill habits change
Future scenarios are easy to imagine. If Spain tightens landfill rules so that organic waste is largely removed and plastic is better contained, these sites would become less attractive to birds. Gulls and storks might revert to more natural feeding patterns in fields, estuaries and coastal waters, and the volume of plastic they move into wetlands would likely fall.
If, on the other hand, plastic production grows and waste management lags behind, landfills could act as even bigger magnets. Bird numbers at these sites might rise, and so would the plastic load reaching protected areas. Given the long lifespan of plastics and the closed nature of some lagoons, today’s choices will shape wetland health for decades.
Originally posted 2026-03-05 04:23:18.