All 3 birds are Gray Flycatchers!
Bird 2 is probably the easiest to id. The habitat is very suitable for Gray Flycatcher and not so much for anything else. The bird is uniformely gray, has a long bill, a rounded head and a short primary projection.
Bird 3 is a little harder. The habitat could work for Dusky, Gray and possible Least. The well-showing bill is simply too long for anything else than Gray Flycatcher. The blotchy breast seems to be a sign of an incomplete molt which is somewhat odd as they normally complete their molt on the breeding grounds.
Bird 1 is difficult, it is yet another Gray Flycatcher. Oak habitat is typically not associated with any of our regular empids. The bill looks shorter in the side profile view than the other 2 birds, but the posture and angles in the pictures are not ideal. It actually is long which may be seen on the singing bird. The head has a slight peak at the back, yet the primary projection is short. This is probably a bird that can only be safely id’ed when it is repeatedly singing/calling.
While there is no recognized subspecies for Gray Flycatcher, it’s hard to believe that the sage-juniper birds mix freely with the ponderosa pine-bitterbrush birds. Same for the oak-pine birds. So, we may well be on our way to a proper subspecies and in the long run to even another species.
All 3 birds sang the same song, a “chlup, chlup” and a “chlup, cheep” with about the same frequency. Soft whits were heard occasionally, particularly from bird 1.
Note that neither of the other more common breeding empids in the Pacific NW (like Western, Willow, Hammond’s) would settle for any of the 3 habitat types. Least Flycatcher could potentially be found in ponderosa pines, but the their bills are just too short.
I watched each bird for over an hour and neither of them was really doing their down-up tail dipping except for one time. It looks to me that Gray Flycatchers singing high on territory just don’t commonly do it. It is when they are foraging, on migration and are otherwise low, when they are likely to dip their tail.