Measuring nest incorporation of anthropogenic debris by seabirds: An opportunistic approach increases geographic scope and reduces costs.

Data on the prevalence of anthropogenic debris in seabird nests can be collected alongside other research or through community science initiatives to increase the temporal and spatial scale of data collection. To assess the usefulness of this approach, we collated data on nest incorporation of debris for 14 seabird species from 84 colonies across five countries in northwest Europe. Of 10,274 nests monitored 12% contained debris, however, there was large variation in the proportion of nests containing debris among species and colonies. For several species, the prevalence of debris in nests was significantly related to the mean Human Footprint Index (HFI), a proxy for human impact on the environment, within 100 km of the colony. Collecting opportunistic data on nest incorporation of debris by seabirds provides a cost-effective method of detecting changes in the prevalence of debris in the marine environment across a large geographic scale.