Plastic pollution off the northwest coast of North America is reaching a surprisingly high level, according to a recent study led by researchers from the University of British Columbia.

The study, published online in the Marine Pollution Bulletin journal, examined stomach contents of beached northern fulmars, a common sea bird in the area, on the western coasts of Canada and the United States.

Northern fulmars search for food exclusively at sea and retain ingested plastic for a long period of time, which made them ideal monitors for marine littering, according to the study.

Researchers quantified stomach contents of 67 fulmars from beaches of the eastern North Pacific from 2009 to 2010 and found that 92.5 percent of these birds had swallowed an average of 36.8 pieces, or 0.385 gram, of plastic. One was even found with 454 pieces of plastic in its stomach.

Plastic ingestion in these fulmars is among the highest that has been recorded globally. Compared to earlier studies in the North Pacific, the findings indicated an increase in plastic ingestion over the past 40 years, according to the study.

To address the worsening situation and protect marine ecology, the researchers proposed an annual monitoring for trends in plastic pollution and the effectiveness of marine waste reduction strategies.