These little birds are rather difficult to identify and I am never entirely confident when naming shorebirds. Shorebirds often look similar at a distance, especially when you are photographing with a camera that sees beyond the naked eye.
I often see these birds congregating with the White Pelicans and at about the same time. These were seen at around 10 a.m. on the upper end of Adobe Creek. Their numbers are currently at the end of their peak and should begin to taper off quickly in August with their peak being from May to July in the Bay Area.