Thanks for your comments, Killian! I have little experience of meena, and I'm not completely certain of how individual features should be weighed, so that's why I wrote that I only get the impression of TD.
Both the primary coverts and the primaries are quite black, the former with very narrow and indistinct light tips, a reliable indicator of juv OTD in my experience.
I agree that the tips of the primary coverts look indeed good for OTD. Here are some photos taken by Magnus Hellström which also illusrate the difference:
OTD:
http://picasaweb.google.se/stenura/DovesCuckosSandgrousesWoodpeckers#5256715597318027234
TD:
http://picasaweb.google.se/stenura/DovesCuckosSandgrousesWoodpeckers#5256715569717425522
However, Magnus wrote here (unfortunately in Swedish) that it is not a 100% reliable feature:
http://www.artportalen.se/birds/gallery_imageinfo.asp?imageID=103498
Personally I have no idea which way it is.
I would say that the tone and pattern of the primary coverts can be much more easily determined in these photographs than is often the case, when they may be largely concealed, or in deep shadow.
Here's an Israeli individual, which is considered to be a TD:
http://www.israbirding.com/israelbirdsforum/forum_entry.php?id=871
On a quick glance, the tips of the primary coverts look better for OTD (at least to me), but if you look closer, you can see some brownish hue close to the tip on the first photo, and at least Mats Waern thinks that the tips fit better TD than OTD. If the photos had been a just little smaller or worse perhaps most people would the primary coverts would have looked better for OTD instead (anyway, the difference to the bird on the Kuwaiti photos, where the bird is more distant, isn't great)...
While the angle is not ideal for determination of the primary-projection, I think it is on the short side, thereby supporting the identification as OTD.
I would agree that the value of the primary projection is debatable, but I wouldn't say that it supports OTD. Here's a Finnish bird identified as a TD for comparison (taken from a similar angle):
http://www.bongariliitto.fi/kuvat/13_Kyyhkylinnut/strtur_20071003_turku_norjy/001_1kv.jpg
Here's a rare comparison photo from Kazakhstan showing both species:
http://www.sofnet.org/apps/image.asp?Path=2&ID=2766&File=Turturduvor.jpg
Judging the relative darkness/lightness of the plumage is very tricky on a lone bird, and the intense light of the Middle East is likely to counter the impression of darkness;
You're of course correct.
One feature that I also mentioned was the extent of black on the outermost tail feathers. The rightmost tail feather seems to be visible in the second photo (see attachment), and the black colouration is almost completely restricted to the inner web. Here's a photo comparing the tail patterns of both species:
http://picasaweb.google.se/stenura/DovesCuckosSandgrousesWoodpeckers#5256715533996647090
The pattern of the Kuwaiti bird is closer to the TD pictured above, but the black still leaks slightly to the other side of the shaft (which perhaps makes it fit better OTD instead?). I have personally no idea of the variation of either species regarding this feature.