I think... juvenile male?
All photos are of the same bird, taken as it hopped about in branches and leaves near the path.
semi-tentative, species has been reported here (muItipIe indvdIs, 'habitat aIso matches'-but not aII too reIiabIe) darkness of bird may be due to photo artifacts/lighting.
It was on one side of the creek then flew to the other soon after; I have pinned the first spot in which I saw it.
Two are just visible here: one toward upper right of photo, one toward lower left. (At the time, I had just seen four of them in flight). Awful photos - taken in haste through the window of a city bus at an intersection, just after realizing what I was seeing! I have absolutely no doubt of the identification: I saw them clearly when in flight, before they landed in the pine trees seen here, and saw the yellow tail feathers on one of them when it took off.