This morning I saw a male blackbird Turdus merula performing a curious courtship display(?) to a female. For several minutes he progressed up and down a short length of wall (about 3m or so): head bowed down, wings drooping, tail depressed, making a constant 'chirruping' sound (not dissimilar to the sound baby blackbirds make to call for food after leaving the nest), A female sat on a parallel fence, about a metre away, watching this.

I've seen thousands of blackbirds - it's about the commonest bird in Britain and a constant resident/visitor in every garden we've had - but I've never seen one do this before. And it doiesn't match the descriptions I found by googling 'blackbird mating display' which all talked about stretching the head up and raising the tail.

Is this documented behaviour?

sorry no-one seems to know the answer to your question.