The first one was Aug 11, 2013, the other yesterday (Sept 7, 13). The molt on the bird yesterday was further advanced, but you would expect that with nearly a month difference in time. However if you look at the right wing here of the Aug 11 bird:
and the right wing here of yesterday’s bird (thanks Tony Brake for taking great photos!)
the pattern of the underwings looks different to me. There is a single dark Greater Underwing covert towards the end missing on the Aug 11 bird. Also the pattern of dark on the inner median underwing coverts differs. On the Aug 11 bird, there are three obvious dark centered feathers here, the outer one with a smaller dark mark, the other two about the same in size. The Sept 7 bird has more dark marks and they get progressively bigger as you go in on the wings. There are other differences I see there as well. On the left side of the face the Sept 7 bird shows a dusky wash at the base of the mandible, bright white on the Aug 11 bird. The Sept 7 bird has a bold and complete white neck band, and a broader white rump patch – these could have changed due to molt in the intervening time though.
Overall my thought is that these are two different birds.