Sorry for chiming in here guys. I usually don't participate in these challenges so I'm probably not allowed to comment either but I'll risk my neck
I am, unfortunately, going to have to agree with Joel on this bird. Apart from some plumage features, this bird just doesn't have the giss of a Petronia. Now I know that a single picture might not represent the giss well so I wouldn't base my conclusion purely on that. However, there are a few plumage features that just doesn't sit right for Yellow-throated Petronia.
1. The bill is too conical for a Petronia. Petronia's, like Sparrows are omnivorous birds and they need to poke their bills into little nooks and crannies from time to time to get hold of a juicy insect. This bird's bill clearly belongs to a seedeater.
2. While the eyebrow of the Petronia can be quite variable in prominence it does extend further to the back of the head, almost meeting on the nape. Also, it is narrower at the eye and tapers out towards the back of the head. This bird has a very parallel eyebrow if that makes any sense. The Petronia actually has a double eyebrow with a darker band underneath the pale band. This bird has only the one eyebrow with some facial markings underneath.
3. Yellow-throated Petronia has very dark legs, like those of Cape Sparrow. This bird has pale brown legs, like those of a House Sparrow (or Long-tailed Paradise Whydah).
4. One very good feature which is visible but perhaps not commonly noticed, is the patterns on the wing coverts, first of all the wing bars formed by the buff tips of the feathers and secondly the actual patterns on the individual feathers.
4.a. The tips of the median coverts are tipped buff in the Petronia which produces an upper wing bar (although not like that of the Petronia but I have no idea how to explain so ignore that for the moment). The second wing bar is absent though as the tips of the greater coverts are not buffy. The edges are buffy though but see the next point.
4.b. I wouldn't even know how to begin trying to describe the actual pattern on the coverts so I drew a quick picture and scanned it in. I'm no artist by any stretch of the imagination but I hope this will get the point across.
The feather on the left is tipped white along the sides with the dark central part extending like a lance to the tip of the feather. This is typically the type of pattern you see on Pipit coverts and the bird in the picture also have such a pattern to the coverts. The feather on the right is "properly" tipped white and the way that the coverts on Yellow-throated Petronia is tipped.
Try to find some pictures online and see if you can spot this very subtle feature or any of the other features for that matter.
One last comment. While the picture doesn't give any impression of size I just wanted to point out that the Yellow-throated Petronia is actually a fairly sizeable bird. I'm not talking Long-tailed Widow size but it is bigger than Cape-, House- or Grey-headed Sparrow and comparable in size to Greater Sparrow. Whydahs, conversely, are small and dainty birds. Like I said, the size is of no help if looking at this picture but in the field it would be reasonably apparent.
I have birded with both Moegaai and Imax and I can vouch for their keen eyes and their ability to ID birds so I don't want to rail them for this one. I wouldn't be surprised if more comes to light on this bird but personally, based on the evidence at hand, I would have to conclude that this bird is not a Yellow-throated Petronia but rather a Whydah and most probably Long-tailed Paradise.And this is not payback for Moegaai pwning me on that Scaly-throated Honeyguide the other day that I got so spectacularly wrong