On our first day in Portland, we visited the famous Powell's City of Books. This place is HUGE. They literally give you a map at the door. This is the bird book section shown here. They had TONS of awesome books including interesting local birding texts, world field guides, and many older books I have never seen. I spent quite a lot of time there looking through them and chatting with a local birder. I also got a kick out of their men's room where people had written every possible play-on-words on the word "grout" on the tile grout above the urinal. It included things like "grout it out loud," "grout at the devil," and tons of others.
Powell's also has a separate store in Portland that just sells technical books. I'm told there's a whole section of ornithological books there. Unfortunately, I didn't get a chance to see that store since I found out about the ornithology section after we had visited the area where it's located.