Hi All,
Yikes! What an interesting bird. Now I can see why there were so many posts and views on this thread. I am really weak on my Marsh Harrier identification, but was wondering about a few points that have come up along the way.
With the caveat that I still get myself tripped up with ageing birds on a regular basis, I am thus far finding myself in the camp that feels this is a first cycle bird (thus a juvenile) rather than one in a later cycle. I don't see any active molt centers and I'm not picking up on any feathers that are of an obviously newer generation. Why not a bird that was hatched in May-June that is now some 3-4 months old? I agree that this bird looks really frayed, but I wonder how much it really is. As with a few other parts of the bird, the remiges have quite an unusual pattern to them, with white tips to many, but with narrow dark streaks extending out to the tips in some cases. There is some fraying for sure, but some of it may be an illusion created by the pigment distribution itself. Since the frayed areas seem restricted to the white patches, it seems reasonable that they could be fraying prematurely due to pigmentation deficiency as others have suggested.
JanJ and Grosser have mentioned the thickness of the primaries being off for a Marsh Harrier. Assuming for a second that it was a juvenile, would that go some way toward explaining the narrower shape to the primaries? It seems like Megaquetzal and Joe's comparative shots show similarly shaped primaries.
As far as potential North American Buteo and Parabuteo go, I think that Harris's Hawk has been reasonably axed. While the bird has some real similarities to Swainson's, there are some real odd features to this bird that I've never seen on Swainson's. First off, Swainson's Hawks frequently exhibit white uppertail coverts, which this bird does not despite having a good deal of white elsewhere. Also the tail lacks any dark tail-barring, which I believe is a feature of all ages of Swainson's. It would be really unusual to see a Swainson's where the wing linings were not noticeably paler than the remiges, and I believe that the remiges should always be barred in that species as well. So anyway, it doesn't add up easily for a Swainson's.
There are a few features that seem reminiscent of Marsh Harrier to me, at least superficially. The general tone of the plumage is plain and dark, without any barring to remiges or rectrices (as with juv. Marsh Harrier), and the uppertail coverts seem to have a tawny cast to them, contrasting with the darker, browner, but tawny tipped rectrices. This also seems to be a really good fit for a juvenile Marsh Harrier (cf. plate 181 Forsman's Raptors of Europe and Middle East). Joe's image in Post #20 shows this somewhat too. Also, is there any import to the shape of the tail? It has slightly concave sides and narrow base when fanned, and seems a good match for at least some of the Marsh Harrier images I've looked at.
Also, there is the nagging behavioral comments from Megaquetzal that the bird looked and behaved like a Marsh Harrier, and it was not until he looked at his images that he was struck by the unusual patterning.
This is a definite head-scratcher, and I'll leave it to those with more experience to work out what it is. But I can still imagine it working out to be a rather weird juvenile Marsh Harrier.
Chris