On a recent visit to Israel, it quickly became obvious that all Whitethroats present (all considered to be of one of eastern races), were spending the vast majority of their time feeding on the ground. This wasn't something subtle, it was really obvious - any sylvia on the ground would more than likely be a Whitethroat, and any Whitethroat found in bushes would quickly revert to hopping about on the ground. Surely others have noticed this in the Middle East?
What is also interesting is that a Whitethroat on the Farne Islands, Northumberland in Nov 2005 also spent much of it's time on the ground (although passerines on the Farnes have little choice). Due mainly to this bird's plumage tones, it was also thought to belong to one of the eastern races.
First photo is bird on Farnes Nov 2005, rest is Israel Mar 2009.