Eating plastic that's floating in the water is so common for seabirds that an estimated 90 percent of them have ingested some form of it, such as bags and bottle caps.
That's according to a group of Australian scientists who analyzed previous scientific literature on 135 seabird species and ran computer models to provide new estimates. They published their findings this week in the journal PNAS.
"This is a huge amount and really points to the ubiquity of plastic pollution," lead author Chris Wilcox of the Commonwealth Scientific and Industrial Research Organization said in a release. He added: "the results are striking."
According to studies published between 1962 and 2012, about 60 percent of 135 bird species had ingested plastic and an average 29 percent of individual birds had plastic fragments in their guts.
"Standardizing the data for time and species, we estimate the ingestion rate
would reach 90 percent of individuals if these studies were conducted today," the authors wrote.
The Australian researchers also predict that by 2050, 99 percent of seabird species will be affected by plastic ingestion -- a problem that will get worse as plastic production increases.
"Global plastic production is increasing exponentially, with a current doubling time of 11 [years]; thus, between 2015 and 2026, we will make as much plastic as has been made since production began," the authors wrote.
The area impacted the most, researchers wrote, is around the Southern Ocean boundary with the Tasman Sea, a stretch of water between New Zealand and Australia. The authors noted that places "where high plastic concentration and high seabird diversity coincide" are most vulnerable.
"We are very concerned about species such as penguins and giant albatrosses, which live in these areas," co-author Erik van Sebille said in a statement. "While the infamous garbage patches in the middle of the oceans have strikingly high densities of plastic, very few animals live here."
The kinds of plastic the birds ingest make their way into oceans from urban rivers and sewers. Birds mistake plastic for food or eat these items by accident. Eating plastic, especially larger items, can be dangerous, even deadly, for these seabirds.
Co-author Denise Hardesty noted that she once found 200 pieces of plastic inside of one seabird. While she doesn't find small pieces of plastic in every bird she studies, it's a common occurrence. “I have seen everything from cigarette lighters ... to bottle caps to model cars," she told the Associated Press. "I’ve found toys."