Observation #3. A final visit to the hawks' nest today revealed that there are four young hawks in the nest, as suggested by photos 1 & 2. Other photos indicate better views of the feathers in the older of the hawks.
Based on the way this young hawk rests its weight on the lower part of the leg, it may be the same young hawk identified earlier has having a possible issue with its right upper leg joint. In any event, the second photo, taken within a minute of the first, seems to show that some weight is being supported on the right leg.