A new guest in our garden

Yesterday I sat on my deck and suddenly I heard a loud twittering coming from our tree. I looked up and saw a bright yellow bird sitting on a branch. It was attacked by the red robin couple because they consider our backyard their home turf. I was delighted and sad at the same time. But later that day it came back. Unfortunately I wasn't fast enough to get a shot but this morning I saw it again and here it is, our new guest: A California Warbler