An alarming new study indicates that seabirds are acting in a bizarre way, and one that is ultimately harmful to their health. The birds are mistakenly eating plastic debris in the ocean not just because it looks like food, but because it smells like food as well.

Many species of seabirds such as petrels and albatrosses use their nose to find krill by detecting dying algae, which is usually a sign that krill are feeding. But the UC Davis study published in Science Advances indicates that plastics are trapping these smells and mimicking their food, accumulating organic matter and putting out the telltale smell.

The scientists tested this theory by floating three types of plastics that are especially common in the ocean off California, putting them in mesh bags attached to buoys so they didn’t float away. Three weeks later, they found the plastic covered with algae, and it smelled like it had been dying, likely drawing birds to it.

“It’s important to consider the organism’s point of view in questions like this,” said lead author Matthew Savoca, who performed the study as a graduate student in the lab of UC Davis professor Gabrielle Nevitt and who is with the Graduate Group in Ecology. “Animals usually have a reason for the decisions they make. If we want to truly understand why animals are eating plastic in the ocean, we have to think about how animals find food.”