Selective occupancy of a persistent yet variable coastal river plume by two seabird species

Advances in telemetry and modeling of physical processes expand opportunities to assess relationships between marine predators and their dynamic habitat. The Columbia River plume (CRP) attracts sooty shearwaters Ardenna grisea and common murres Uria aalge, but how seabirds respond to variability in plume waters is unknown. We characterized seabird distributions in relation to hourly, daily, monthly, and seasonal variation in CRP location and surface area by attaching satellite telemetry tags to shearwaters in 2008 and 2009, and to murres in 2012 and 2013. We matched seabird locations to surface salinity from a high-resolution hydrodynamic model of the CRP and adjacent waters. Utilization distributions indicated high-use areas north of the Columbia River mouth and in continental shelf waters. Shearwater and murre occupancy of tidal (