The Desert Lesser Whitethroat on Teeside
Brian J Small
The accompanying images were taken using a Sony PC-3 through a Leica APO Televid with 20X eyepiece. Bright light produces a great deal of contrast.
I wonder how many birders failed to travel to South Gare, Teeside, in order to see the Desert Lesser Whitethroat Sylvia [curruca] minula, present from November 9th-26th 2000, because of its status as a sub-species of Lesser Whitethroat. Of those that did how many were amazed to find a bird so different from their pre-conceived ideas of what a Lesser Whitethroat should look like. Few that saw it could not have been struck by its small and diminutive size – it was clearly smaller than a nominate Lesser Whitethroat – and its structure and behaviour. Indeed, it was so like a Desert Warbler S. nana in colour and shape and behaviour that you would keep looking for the rufous tail; it was difficult to believe it was a ‘Lesser Whitethroat’.
Value was added by the bird’s ability to change colour and tone according to light – two birds in one. At times, it would appear fairly like Lesser Whitethroat, with the greyness enhanced, it would then look ashy grey on the head similar to Barred Warbler S. nisoria, darkest around the forehead, lores and ear coverts, grading through sandy grey on the hind neck to sandy brown on the upper-parts; the under-parts would appear paler with a pinkish suffusion on the breast and flanks. At other times, it would appear almost wholly sandy, slightly greyer on the head – the colour of Eastern Desert Warbler S [n] nana; even the upper-tail coverts looked sandy grey and at such times the under-parts looked pinkish buff, giving it a more uniform coloration
The short and fine bill was clearly different to that of curruca, and similar to the smaller Sylvia warblers. The dark upper edge and tip to the upper mandible and tip to the lower contrasted with the flesh yellow cutting edge and base – again unlike the greyer bill of some other races (curruca, blythi, halimodendri). The legs were fine, generally dark grey, but with pale yellowish soles. The eyes were a pale, milky pinkish brown.
The call was noted as a ‘trrrr-tuc’.
Taxonomy
The taxonomy of the Lesser Whitethroat group is a complex and thorny issue, with, as ever, a variety of opinions. Put simply, there are three groups: the western and northern races curruca, blythi and halimodendri (known as Lesser Whitethroat); the eastern desert races of NW China, Mongolia and into Turkestan, minula and margelanica (known as Desert Lesser Whitethroat); and the mountain dwelling althaea, from NW Himalaya, probably west to NE Iran and Afghanistan (known as Hume’s Lesser Whitethroat). Althaea is most distinct and probably merits specific status, whilst the difficulties in splitting the other groups is the apparent clinal grade of features, with halimodendri being the link between the browner curruca and blythi and the paler and sandier minula and margelanica – some eastern halimodendri can apparently be very like Desert Lesser Whitethroat (Lars Svensson, pers com). Other forms, e.g. caucasica or telengetica, are treated as synonymous with Lesser and Desert Lesser Whitethroat respectively.
Lars Svensson has commented: "I favour a grouping of ONE, but I am quite open to suggestions of having two groups, these two then being Sylvia [curruca] curruca (containing halimodendri, minula and margelanica as subspecies) and Sylvia [curruca] althaea. This is a possible and perhaps sensible arrangement, since althaea seems to have come a far way towards becoming a reproductively isolated, ecological species, selecting alpine and semi-alpine habitats, whereas halimodendri and minula stick to valleys, foothills, semi-deserts and arid plains."
I am especially grateful to Lars Svensson for his valuable comments and to Richard Millington at Birding World for the discussion surrounding this great bird.