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Distributions of Shearwaters and Murres Associated wtih the Columbia River Plume

Released: 2017
Citation:
Phillips, E.M., J. Adams, J.E. Zamon, J.K. Horne. 2017. Distributions of Shearwaters and Murres Associated wtih the Columbia River Plume. Pacific Seabird Group 44th Annual Meeting, Tacoma, WA. 22-25 February 2017.

Discharge from the Columbia River into the northern California Current creates a large, dynamic plume and multiple plume fronts. These nutrient-rich waters fuel primary and secondary production, supporting a diverse food web that includes small pelagic prey fish, large populations of Pacific salmon, marine mammals, and seabirds. Sooty shearwaters (Ardenna grisea), common murres (Uria aalge), and prey including northern anchovy (Engraulis mordax) and juvenile salmon (Oncorhynchus spp.) occur disproportionately in the Columbia River plume during May and June, indicating that the plume is a foraging area. The distributions of shearwaters and murres within the plume differ, however, and may relate to species-specific differences in foraging ecology, especially during the spring and summer when breeding murres act as central place foragers, while non-breeding migratory shearwaters are free to disperse. To quantify differences in shearwater and murre distributions, we used satellite transmitter data to estimate Brownian bridge utilization distributions (BBUD) for each species. To evaluate associations with the dynamic plume, we compared BBUDs to predicted surface salinity values from a freshwater circulation hindcast model. Greatest BBUD values for shearwaters were near the northern edge of the plume, regardless of plume size or location. Greatest BBUD values for murres were in central plume waters or to the south, nearest to breeding colonies. However, we did not observe obvious central place foraging behavior in the murre telemetry data, indicating that other factors including access to shallower prey or niche partitioning, possibly due to interference competition, may be important.


This product is associated with the following project:
Common Murre associations with the Columbia River Plume and adjacent waters

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