Whilst birding the Al Jouf area of northwest Saudi Arabia we came across some pale looking Desert Lark Alauda deserti near Sakaka, resembling A. d. isabellinus. Geographical variation in Desert Lark is complex, and numerous races have been named mainly on the basis of plumage coloration. The colour of the birds appears to be directly related to the colour of the local soil and rocks with birds from sandy habitats are mostly buff-coloured, those of stony or rocky ground various shades of grey, rufous, or brown with blackish races living in black lava deserts. Confusingly, pale and dark birds occasionally live side by side in some areas and bleaching and abrasion have marked effect on colouration and produce further complications often making sub-specific identification difficult. A. d. isabellinus occurs from northern Egypt, east to south and east Israel, southern Jordan, north-west Saudi Arabia and southern Iraq and is small and pale, generally light sandy to pale buff-brown with greyish or pale olive-grey tinge above, buff or creamy buff below, tail rufous with triangular black area at tip. Birds presumably of this subspecies occur throughout northern Saudi Arabia gradually becoming plaler towards the east becoming pale cream similar to A. d. azizi, which is the subspecies that occurs ear to me in the Eastern Province of Saudi Arabia around the Hufuf and Shedgum areas and is the palest race with pale creamy plumage. It is clear there is some difference between colouration, bill size and tail colour of many of the birds in Saudi Arabia but how much of this is clinal is unknown.
