Fig. 4.
Changes in A. numerical abundance and B. mass of plastics in fulmars from the Netherlands since the 1980s. Data show arithmetic averages ±standard error (SE) by running 5-year averages (i.e. data points shift one year ahead at a time; sample size for 5 year periods is ≥ 21 during the 1980s and ≥204 from the 1990s onward. Data in the early 1990s were omitted because sample sizes were ≤10 birds. Details in Online Supplement.