It seems that the warblers come back to us from Africa in phases; first comes the chiffchaff, then the willow warblers, the blackcap next, and then, in late April, the whitethroat (Sylvia communis).
As I wander the hills of the Purbeck coast and the ridge these, and their close cousin the lesser whitethroat, can often be heard but not always seen on scrub, gorse, hedgerows and bramble. Their 'song' is a rasping, vigorous, rambling, continuous chatter and this is the best way to tell them from the 'lesser' which has more pattern to its song, a bit like a chaffinch with a sore throat! To tell them apart visually you need a good look. The 'lesser' has a greyer back rather than brown, the underside is white rather than buff and the face has a dark grey 'mask' around the eyes.
The whitethroat is not as common as it once was. Back in the 1960s their population was steadily increasing and then disaster struck in the spring of 1970. Their migration passage back means they have to cross the Sahara desert and that year the timing of that journey coincided with strong winds and severe dust storms in the desert and countless birds were lost. The numbers that made it back were a small fraction of previous years population and they remained quite scarce for some years but gradually they do seem to have recovered somewhat. It just shows what a dangerous and exhausting strategy migration is but it must work or they would not do it.