My family and I spent a week on Oahu at the end of March for a spring break trip. This was definitely not a birding trip and the only birding I did was opportunistic. There's not a lot of diversity but still some fun things to see.
We were staying at a resort at Ko Olina on the southwest coast of the island. Fortunately there was an empty field outside our room, which provided a few species:
Common Mynas were everywhere (the equivalent of parking lot house sparrows or Brewer's blackbirds):
I was amazed at how many Pacific Golden-Plovers there were. They were in every field, medians in the road, etc. They were even walking around the pool deck: