A huge new study is making the groundbreaking claim as to why seabirds are behaving in a way that is both strange and harmful to their health. The study found that seabirds are eating plastic debris in the ocean not just because it looks like food, but because it smells like food as well.

Albatrosses, petrels and other seabirds rely heavily on their sense of smell to find krill to eat. Their noses can detect the smell given off by dying algae, which is a telltale sign that krill are feeding nearby. But algae also sticks to plastic debris and gives off the same sent, tricking the seabirds into eating something that is harmful to them, according to the UC Davis study, which was published in the journal Science Advances.

Scientists came to their conclusions by putting out three types of plastic trash and tethering it to a buoy. After three weeks, the plastics were coated with dying algae, likely drawing seabirds to them in search of an easy meal.

“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.”

“This study shows that species that don’t receive lot of attention, like petrels and some species of shearwaters, are likely to be impacted by plastic ingestion,” Nevitt said. “These species nest in underground burrows, which are hard to study, so they are often overlooked. Yet, based on their foraging strategy, this study shows they’re actually consuming a lot of plastic and are particularly vulnerable to marine debris.”