Sorry about the late reply!
I couldn't say for sure as I know very little about the species but I think you're probably right.
In another picture I took the feathers were visibly still brown rather than the adult black and the beak is even lighter towards the end.
The beak colouring is correct for a adult but the plumage colouring you describe gives me the impression of a second summer bird this meaning coming out of juvenile into adult plumage.
Just for the record males and female adults are exactly the same colouring in plumage and beak just that the male is slightly taller than the female and the juveniles have a olive greenish coloured beak with brownish tinting to the plumage untill around 12 months old hope this helps.
