This is a lekker challenge. I will always be hesitant to appear too confident of juv/fem ringtail ID's but I'd like to pitch in on this one with a vote for juvenile Monty's. Seems I'm going against the majority thinking though but here are my comments:
First of all, when ID'ing ringtails it's important to first establish whether the bird is a juvenile or an adult female. The fact that this bird has virtually no streaking to speak of on chestnut underparts, is contrastingly dark on the upperparts and sports a bold facial pattern I would say it's a juvenile.
Now on to the plumage features that I think I can pick out from these pics. Most, to my mind, point to Monty's Harrier but some actually do point to Pallid as well. I'm writing the features that point to Monty's in blue
and those pointing to Pallid in green
1. The base of the primaries lack the pale colouration that forms the Pallid's pale "boomerang" on the underwings.
2. Not only are the primaries (seen from below) of Pallid plain at the bases (giving the pale boomerang pattern) but they are also paler towards the tips. In other words the barring on the primaries is restricted mostly to the central area. On Monty's the barring extends evenly all the way to the tips of the feathers with a darker trailing edge. I have to be honest though that I think the picture of Lizet's bird can go either way on this feature. The bird does seem to have a nice dark trailing edge
on the primaries but then the barring is very difficult to pin down as it does start right at the carpal joint
but does not really extend to the feather tips
3. On both the underwing and the upperwing the primaries appear to be a shade or two lighter than the secondaries.
This is a feature of Pallid Harrier but it is also a feature of juvenile ringtails in general. I'm not sure how useful this is when you're trying to seperate a juvenile Monty's from a juvenile Pallid.
4. Still looking at the underwing, the pale subterminal band shows what I think are three fairly important characteristics:
a. It is broader than the dark terminal band (would have been narrower in Pallid).
b. It is evenly broad over its entire length (on Pallid it would have tapered from broad at the primaries to very narrow close to the body).
c. It is evenly pale over its entire length (not getting darker closer to the body as with Pallid).
5. As regards the upperwing I'm not really sure what to make of it. Like I said above the secondaries are darker than the primaries
and also there appears to be no significant barring on the upperwing
. Both of these are features that point to Pallid but then they're probably true of juveniles in general. I'm not sure. The bird does seem to have a darker band at the base of the secondaries which would point to Monty's.
6. The facial pattern is indeed quite bold but I don't think this is enough to lead one to ID it as Pallid. It is what leads me to believe that the bird is a juvenile. However, the dark line through the eye is fairly indistinct. The supercilium is very broad (would have been quite thin on Pallid) and the supercilium merges with the white cheek to form an extensive white area around the eye. I believe all of these to point strongly towards Monty's.
7. The underparts should show at least some streaking on the sides of the breast and on the flanks. I can't seem to pick up any streaking really and this points to Pallid.
8. The barring on the tail (above and below) holds another key. On Monty's the dark bands are all the same thickness and the same colour while on Pallid the last band is usually darker than the others and also thicker. Lizet's bird shows evenly sized and coloured dark bands.
9. Looking at the undertail, a feature that is particularly useful with juveniles is that on Pallid Harrier the outer tail feathers are pale with only a dark subterminal band visible. This gives their undertail, especially when spread as in Lizet's picture, a pale outside frame. On Monty's the outer tail feathers are barred and coloured exactly like the rest of the tail feathers and the barring on the undertail of Lizet's bird extends right to the edges.
One of the reasons why these ringtails are so difficult to identify is because the features are often quite arbitrary and there exists some overlap between the two species. There aren't really any diagnostic features and you are often left to identify the bird based on a collection of features. In my opinion this bird shows enough features congruent with Monty's Harrier that I would have identified it as such - but that's just me