This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: What seabirds eat might seem like a good starting point for identifying species that tend to accumulate plastic in their digestive systems. Yet a recent global analysis suggests that mapping the evolutionary relatives of birds could offer better clues than their diets or feeding methods alone.
Researchers at the University of Queensland, London's Natural History Museum and other institutions assembled records covering 93,281 birds belonging to 240 distinct species. In their models, outlined in Biology Letters, evolutionary relationships were found to be the strongest predictor of plastic occurrence in seabirds. In contrast, the birds' diet, feeding method, body size and specialization in open-ocean feeding showed no consistent effects after the researchers accounted for relatedness and differences among studies.
The researchers combined information from 262 sources published between 1958 and 2024. They focused on the proportion of birds in each sample that presented signs of having consumed plastic, rather than the number of plastic pieces each bird contained. This widely available measure, known as frequency of occurrence, allowed the team to compare the findings of many studies.
They found that plastic had been recorded in 182 of the 240 sampled species. This means that about three-quarters of sampled species (not individual birds) had at least one record of plastic ingestion. The researchers then produced models using records covering 82,406 birds from 230 species.
They excluded species lacking complete ecological information and samples consisting solely of nest-bound chicks, which do not forage for themselves. The team compared records of plastic occurrence with the species' lifestyles and positions on an evolutionary family tree, which represents their shared ancestry. Their models accounted for differences in the sampling methods employed across studies, study years, publications, the age groups of the birds and the ocean basins considered.
Closely related species tended to show similar patterns of plastic occurrence. "This does not mean ecological traits are unimportant," the researchers wrote in their paper. Related species often share feeding habits and other characteristics, including traits that the analysis did not measure.
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