In addition to hoped-for seasonal goodies (Lazuli bunting, western tanager, black-headed grosbeak, migrant warblers, flycatchers), I had two unexpected finds, birds that I associate with Black Diamond Mines rather than Mt Diablo: Phainopepla and Canyon Wren.
Near the beginning of the trail, on the west side. There is a derelict, farm-like work area behind the park residence visible from the Mitchell Canyon trail. It is distinguished by three, blue, plastic (water storage?) tanks. Phainopepla was in the oaks there.
Canyon Wren location
Roughly 3 miles up the trail. After the Mitchell Canyon trail begins its ascent to Deer Flat and clears out of riparian habitat, the view of the opposite side of the canyon (to the east) opens up. Canyon wren was singing from the sheer cliff face there.
Apologies in advance to others if these birds have already been reported.