Gull

Definitely has Glaucous-winged genes in it, hence the creamy white primaries. The annoying thing is, in some parts of the northwest, hybrids and backcrosses outnumber pure birds and often times definite ID is impossible if you're not a gull expert. Personally, I'd lean Western x Glaucous-winged hybrid because the plumage is more mottled than subdued and the build is more hefty, indicative of Western Gull background.