Southern Oahu, although crowded, is home to numerous birding spots. Marshes on the western side of Pearl Harbor attract wintering waterfowl and shorebirds, while the valleys and ridges of the south side of the Koolua Mountain range are home to Oahu’s two endemics. If staying in Honolulu all of the southern spots should be reachable within 30 min (as long as it isn’t during rush hour).