At first I thought it was a small airplane, small-ish, very tiny but I kept looking and you cannot mistake a white head and a white tail; could have mistaken it for a large hawk such as a red tail but nope, an adult bald eagle in all its might. Two or three years ago we took our son to a summer camp, around Stanford on 280, a bird crossed the freeway in front of us, a bald eagle, also adult; I told my family to look at it, they were either arguing or trying to chose someone's tunes over the others.
They are a rare view in the metropolitan area.