Given that the whole complex has until recently been known as Isabelline Shrike (and was once collectively known as Red-tailed Shrike) it seems a shame to me that both IOC and Clements have gone with re-using those names for the two "new" species. I understand that there are good reasons for abandoning the alternative common names Daurian Shrike and Turkestan Shrike (I gather the implied range is inaccurate) but these names were already in common usage and make it clear whether you're referring to the new split taxa or the old lumped taxon. So being a bit stubborn I will continue to use Daurian Shrike in this post to refer to the new Isabelline Shrike Lanius isabellinus and Turkestan Shrike to refer to the new Red-tailed Shrike Lanius phoenicuroides.
Anyway, this post is about their ID not their taxonomy or nomenclature. Prior to heading out to Oman in November 2017 I'd intended to swot up on all the tricky ID conundrums I was likely to face when I got there. In the end I ran out of time and one of the species pairs I didn't swot up on as much as I would have liked was the "Isabelline Shrike" complex. I already had a certain degree of familiarity with Daurian Shrike as a result of experience with a small handful of vagrants in the UK (such as the one at the top of this page) but no experience at all with Turkestan Shrike. I had some awareness of some ID features of some Turkestan Shrikes (for example I knew that darker brown birds with strongly contrasting rufous crowns were likely to be Turkestan), but I was also aware that many birds were much tougher than this.
In Oman we found a great deal of variation among the 29-30 birds we saw and undoubtedly both species were encountered. Some we left unidentified in the field, others we tentatively identified and a few we identified with a higher degree of confidence. Upon returning and after a bit more research I feel that many of our tentative identifications where we erred on the side of Daurian were in fact Turkestan and Turkestan may possibly have been the commoner of the two.
Below I present all the birds that I photographed out there with some brief commentary on how I have (or haven't) identified them. I fully appreciate that one or two poor quaility photos may not be sufficient to derive a positive ID but I am also hoping that others with a bit more experience may be able to chime in with some helpful comments. I would be especially grateful for correction if anything I have concluded is incorrect.
1) Al Qurum Beach (Muscat), 3rd November 2017
This was considered to be Daurian isabellinus inthe field and may be so. The supercilium is weak supporting that ID and while the forecrown is clearly reddish (more obvious when head-on) the bright colour is restricted to the front of the crown. Making me uneasy about this ID is the apparently whitish background colour to the underparts, throat and supercilium. The quality of the photo may be impacting this but I would expect a Daurian isabellinus to show more buffy underparts, so I wonder if this may in fact have been a Turkestan Shrike phoenicuroides?
2) Al Qurum Beach (Muscat), 3rd November
A second bird at the same location as the last, this time presumably an adult. Again this was considered to be Daurian isabellinus in the field and indeed the apparent lack of warm tones in the crown seems to eliminate typical Turkestan phoenicuroides, but the 'karelini' morph of Turkestan may be possible. The extent of the buff wash on the underparts probably favours Daurian isabellinus but the throat appears whiter and this bird has a prominent whitish supercilium which I would have thought was more a feature of Turkestan phoenicuroides. It appears to have a pure white primary patch which may also favour Turkestan Shrike.
3) Al Qurum Park (Muscat), 4th November
This bird was quite distantly photographed but I assume the extensive buff wash to the underparts, throat and face were not entirely down to an effect of the morning sunshine. There appeared to be very little contrast between the upper and underparts and I believe our field ID of Daurian Shrike isabellinus must be correct.
4) Hilf Water Treatment Works (Masirah), 6th November
This approachable bird was considered to be Daurian isabellinus in the field but after further research I am favouring Turkestan phoenicuroides. The crown was reddish - not strongly so but it is clear in all the images where the head is turned slightly away or tilted downwards (only one photo out of half a dozen doesn't show this). There is a buff wash on the underparts but this is very faint and it seems not to extend to the throat - there is substantial contrast betwween the whitish underparts and the brown upperparts. It has a relatively prominent whitish supercilium and some barring on the front half of the crown which I believe favours Turkestan Shrike phoenicuroides.
5) Hilf Water Treatment Works (Masirah), 6th November
This bird was first seen in a bush right next to where we were standing and allowed us to look directly up at it while it preened. At first its plumage was in such a state having apparently just taken a bath that it was difficult to interpret colour tones but its condition improved as we watched it. Again this was identified as Daurian isabellinus in the field but I now think there are a number of features pointing to Turkestan phoenicuroides. The buff on the underparts is restricted to the flanks, it has an indistinct but whitish supercilium (perhaps a little buff in front of the eye) and the crown is barred. The upperparts are grey-brown lacking sandy tones. Taken together I think this all points to Turkestan Shrike phoenicuroides?
6) Qitbit (Dhofar), 8th November
In the field the darker brown upperparts of this bird compared to most seen up to this point, and stronger underpart barring, made me wonder if it was a Turkestan phoenicuroides and this may be the case. Unfortunately the photos are quite poor and it is impossible to be sure of true colour tones. However there seems to be a contrastingly strong buff wash to the rear flanks shown on the left hand photo but no other sign of buff across the underparts, which supports the Turkestan ID, but the supercilium is weak and there doesn't appear to be much if any barring on the crown. The barring on the underparts seems to be more extensive than on most birds seen during this trip and there is even some barring on some upper scapulars and/or mantle feathers which I did not notice in the field. This in combination with the rather dark upperparts and seemingly dark brown tail made me contemplate Red-backed Shrike collurio briefly but there are plenty of reasons to discount that. I suppose it could be a hybrid x Red-backed Shrike but I suspect it is a pure Turkestan Shrike phoenicuroides.
7) Qitbit (Dhofar), 8th November
Unlike the last one from the same place, this one was identified as Daurian isabellinus in the field. The upperparts are certainly a paler sandier colour and there is minimal warmth in the crown. However there appears to be virtually no buffish tones to the underparts or the supercilium which is reasonably obvious. There is faint barring on the forecrown although this doesn't seem to be very extensive. I'm really not sure about this one but perhaps leaning slightly towards Turkestan Shrike phoenicuroides.
8) Muntasar (Dhofar), 9th November
A distant adult at Muntasar was not photographed but was quite different from any shrikes seen previously being darker brown above contrasting strongly with the whitish underparts which were quite strongly barred. The cap was noticeably reddish and I felt confident that it was a Turkestan Shrike phoenicuroides, a view that has not changed following further research on my return home.
9) Muntasar (Dhofar), 9th November
I think I suspected Daurian isabellinus for this one in the field but now I am not sure. Supporting the Daurian ID is the fact that there is virtually no pale supercilium. There is quite a bright rufous forecrown which isn't ideal but I don't think this rules out Daurian. There is a strong buff wash on the flanks but this appears to fade quickly so that the rest of the underparts are whitish. However the true tones are hard to assess in these digi-scoped photos and I don't feel able to put a definite name to this one at the moment. I'm still favouring Daurian Shrike but remain open-minded.
10) Ayn Tobruk (Dhofar), 11th November
This adult was at the camel-drinking trough and was mostly seen looking into the sun, and we were somewhat distracted by Arabian Golden-winged Grosbeaks. At the time I called it as Daurian isabellinus but looking at the photos that must surely have been a mistake. Although the crown isn't strongly reddish its more so than the grey nape and grey-brown mantle, and it is bordered by a very distinct whitish supercilium (though it doesn't look equally distinct in all photos - most obvious when the bird is facing the camera slightly). The warmth of the flanks contrasts with the relatively white belly and even if any buff tones to the belly are lost by the exposure, the throat is in shade and still appears pure white. This must be a Turkestan Shrike phoenicuroides, mustn't it?
11) Mughsayl Kwahr (Dhofar), 12th November
This bird along the track running up the west side of the kwahr was identified in the field as Turkestan Shrike phoenicuroides. The photos are poor but they show its brown upperparts with a strongly contrasting reddish crown and whitish underparts.
12) Khawr Rawri (Dhofar), 13th November
Although the forecrown is quite bright the pale sandy upperparts contrast relatively weakly with the buff-washed underparts. There's no supercilium to speak of - surely this must be Daurian Shrike isabellinus?
13) Wadi Muqshin (Dhofar), 15th November
This bird shows some similarity to bird 6 with its dark brown upperparts, extensive and prominent dark scalloping underneath and hint of barring on the scapulars. Unless I'm much mistaken this one falls firmly into the Turkestan Shrike phoneicuroides camp.
14) Al Qurum Park (Muscat), 18th November
Although the rufous tones to the crown prompted at least one observer to suggest Turkestan phoenicuroides I think this is a straightforward adult Daurian Shrike isabellinus. There is little contrast between the sandy brown upperparts and the strongly buff-washed underparts.
Please do comment or send me an email if you have anything helpful to contribute to these. I'd be particularly interested to hear from you if you think I've got anything wrong or misrepresented anything, or if you have any additional tips that I've overlooked, but I'd also welcome confirmatory comments if you think I'm bascically on the right track.