After searching for over 3 hours around President's Island, I decided one last time to check the area where the three birds were first located. After sitting and watching birds come and go, I heard the distinctive calling of a White-wing and it was quite close. The sound seemed again to be coming from the ground but moving around to different locations on the street, nothing. Finally, scanning the short Cotton Wood Trees, I found the bird sitting (smaller bird on left) next to a Collared-Dove about 3 feet off the ground.