Thanks. Yes, juv. bl-throated seems plausible, especially the broadly spaced breast-side streaking is a distinct feature pointing in this direction. However, I was puzzled, because the yellow on the bird's head is much more limited than in any of the literature I have around (the Sibley, Kaufmann, and National Geographic guides). The bird on the photo has yellow patches on the crown, and quite weakly just below the eye and forward towards the throat. Typical bird guide illustrations/photos in addition show strong yellow eyebrow and a yellow collar from the beak to the neck.
Perhaps this sort of variation in the plumage is just normal?