By 2050, nearly 200 species of seabirds—from penguins to petrels—will be eating plastic. But what attracts them to this often-deadly debris is more than its resemblance to a tasty morsel of jellyfish or seaweed. The smell of plastic, when fouled by algae, is also attractive to some seabirds, suggests a new study. To find out how this happens, researchers strapped mesh bags full of three types of plastic beads to buoys off the California coast. They found that the floating beads picked up a chemical called dimethyl sulfide (DMS), a byproduct given off by algae and other microorganisms as they break down (usually when they’re being eaten). Because the algae-eaters are themselves seabird prey, DMS serves as a dinner bell for many species of foraging seabirds, which home in on patches of DMS-rich water and scoop up whatever foodlike items are there. And chemical analyses suggest that it takes less than a month for some types of plastics to pick up the telltale scent, the researchers report online today in Science Advances. Because similar plastic beads straight from the manufacturer don’t emit DMS, it’s likely that the scent comes from algae growing on the surface of the beads and from DMS that they adsorb via exposure to seawater. The team also found that DMS likely plays a key role in plastic ingestion: Only 8% of birds that don’t respond to DMS ate plastic, versus 48% of birds that use it as a feeding signal. The team hopes that an answer to the birds’ plight will come through science, likely in the form of new plastics that don’t get fouled by DMS-producing organisms.