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When species competing for the same resources coexist, some segregation in the way they utilize those resources is expected. However, little is known about how closely related sympatric breeding species segregate outside the breeding season. We investigated the annual segregation of three closely related seabirds (razorbill Alca torda , common guillemot Uria aalge and Brünnich’s guillemot U . lomvia ) breeding at the same colony in Southwest Greenland. By combining GPS and geolocation (GLS) tracking with dive depth and stable isotope analyses, we compared spatial and dietary resource partitioning. During the breeding season, we found the three species to segregate in diet and/or dive depth, but less in foraging area. During both the post-breeding and pre-breeding periods, the three species had an increased overlap in diet, but were dispersed over a larger spatial scale. Dive depths were similar across the annual cycle, suggesting morphological adaptations fixed by evolution. Prey choice, on the other hand, seemed much more flexible and therefore more likely to be affected by the immediate presence of potential competitors.

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Plastic pollution is a ubiquitous global environmental problem. Plastic ingestion by seabirds is an increasing issue even in remote areas, such as the Arctic, yet research and monitoring of plastic ingestion in Arctic seabird populations is limited and there are large knowledge gaps for many geographic regions. There is currently no standard technique for monitoring plastic debris in the Arctic, making it difficult to compare studies and monitor global trends. Here, we review the current state of knowledge of plastic ingestion by seabirds in the Arctic. We analyzed 38 published records that report plastic ingestion by seabirds in the Arctic region. Of the 51 seabird species examined for plastic ingestion in the Arctic, over half have ingested plastic, however the majority have a limited number of studies, small sample sizes, and/or data are more than 15 years old. Additionally, the spatial distribution of plastic ingestion reports in the Arctic varies widely, with large knowledge gaps in the northernmost areas of most countries. This indicates that we lack recent information on plastic ingestion for the majority of seabird species in the Arctic. Further, less than one third of studies references standardized methods from other regions, making it difficult to assess spatial and temporal trends. Long-term monitoring programs should be established in the Arctic to obtain an accurate assessment of plastic ingestion by seabirds in this region.

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