Arctic Biodiversity Climate change

Non-breeding ecology of thick-billed murres from the only colony in the western Canadian Arctic

Paredes, R., Orben, R., Will, A. & Insley, S.

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Key points

• Males and females migrate and molt in different places during the fall but are together during the winter and spring, so they face different risks, especially during their flightless molt period when they can’t escape disturbance.
• Outside the breeding season, murrelets feed mainly on fish, so climate change or human activity could adversely affect their health.
• The Beaufort, Chukchi and Bering seas are key wintering and migration areas. Growing threats such as increased shipping traffic, storms and possible oil spills along this route could seriously affect this small population.
• Cape Parry murrelets can serve as early warning indicators of changes in the Western Arctic, helping to guide conservation measures aimed at protecting them where and when they are most vulnerable.

Abstract

Cape Parry, Northwest Territories, Canada, is home to one of the smallest, most remote, and least studied populations of thick-billed murres Uria lomvia globally. Here, we report on the spatial distribution using biologging, and trophic levels and nutritional stress using stable isotope and corticosterone analysis of feather samples, of 41 murres (15 females and 26 males) from this population during the 2021-2022 non-breeding period. In the fall, murres migrated westward, and core-use areas were mainly on the continental shelves of the Beaufort, Chukchi, and northern Bering Seas. Their migratory speed corresponded with sex: most males, likely traveling with chicks, were slow migrants (73%), while effectively all females (93%) were fast migrants. Sex differences in core-use areas and timing only occurred in the fall and suggest that the flightless period (flight feather molt) occurs in the Chukchi Sea for females and the Amundsen Gulf and eastern Beaufort Sea for males. Both sexes wintered in the northeastern Bering Sea. Spring migration was synchronous, beginning in early May coinciding with ice breakup in the Chukchi Sea. Fall was a more energetically constrained period than winter for murres, and those with higher trophic level diets (δ¹⁵N) originating from a more near-shore food web (δ¹³C) incurred lower nutritional stress. Throughout the non-breeding period, murres tended to forage at higher trophic levels, likely consuming more fish than invertebrates. Our results highlight the importance of identifying and mitigating threats to Cape Parry thick-billed murres as they migrate, stage/molt, and overwinter in the Beaufort, Chukchi and eastern Bering Seas.

Recommended citation

Paredes, R., Orben, R., Will, A. & Insley, S. (2025). Non-breeding ecology of thick-billed murres from the only colony in the western Canadian Arctic. Marine Ecology Progress Series. https://doi.org/10.3354/meps14970