Hi again and sorry for the delay.
First of all I'm attaching a Dropbox link to the well-known Dutch Birding article (Worfolk) on these shrikes. I'm not sure how much our knowledge has advanced since it was written in 2002. One key point the article makes is that around 10% of rufous-tailed shrikes are not identifiable, many individuals showing intermediate characteristics. Classic individuals are not too difficult but if you look at some of the images, you'll see that there are plenty of individuals showing characteristics of both
isabellinus and
phoenicuroides. We get some here in the UAE.
I didn't have a clear idea where Kyrgyzstan is until I looked it up, but looking at the range map in the article, it seems to fall more in the range for Turkestan AKA Red-tailed than Isabelline, although it might also fall in the range of
arenarius. This taxon, if it exists at all, is probably a subspecies of Isabelline and is generally dull, washed-out looking and rather uniform in appearance, lacking the blackish flight feathers of the other two taxa. It looks like there might be a hybridisation zone (
arenarius x
phoenicuroides) in or around the country. This might explain the intermediate appearance of some of these birds. It's also possible that
isabellinus from further east could go through the country on passage. Kyrgyzstan is also quite close to the hybridisation zone 3 on the map, where both
isabellinus and
phoenicuroides AND
isabellinus and
collurio (Red-backed) are known to interbreed. There's also an intermediate zone between Red-backed and Brown not too far away! If this map is still accurate, heaven knows what could go through Kyrgyzstan on passage....
https://www.dropbox.com/s/x7tydk03phltgds/DB_2000_22_6.pdf?dl=0
Looking at your new images, the bird you've labelled aaa (and aaaa?) seems to be the same individual as Alcarmist 5. I'm not sure what it is, but the sandy-brown upperparts, brown ear-coverts, weak barring, weak rufous coloration on the rump, brown flight feathers and pale lower mandible aren't right for Turkestan. However, the bird seems rather clean white on the underparts and throat. My best guess is that there's some
arenarius influence there.
Even more difficult is the bird labelled aaaaa. It doesn't look much like an Isabelline to be honest. The mask is broad and heavy, as is the supercilium. The throat looks whitish,the upperparts greyish-brown. The big problem is the amount of gingery wash on the flanks, far too much for a Turkestan. I did wonder about Brown Shrike but it doesn't look right for it structurally (head not large enough, tail too short?). It's a little like image 334 in the article, which I don't think can be
isabellinus. I saw a bird like this in the UAE last autumn too.
I would really appreciate some more input on these.
