This is Mom and her three nestlings on May 12. The nestlings appear to be a few days apart in age. (This photo represents the first and only time I saw three nestlings; in future visits I confirmed only two, and have no idea what happened to the third.)

My best guess is that the nestlings here are about three weeks old. (The second, perhaps older, nestling is hidden by the foreground tree limb.) Note he/she is still carrying quite a bit of down. The other nestling appears to be more fully feathered.

The mother (?) attended the nest almost constantly during the early days, feeding and cleaning the babies, or warming them underneath herself. The mate dropped off rodents or small birds, which the mother stored in the nest until feeding time. These brief visits were accompanied by much calling between the adults; since they appeared identical, I couldn't tell if they swapped places or if one foraged while the other tended the nest exclusively. (I suspect the latter.)