Colin PMd me in the first instance, requesting the translation as I have not been watching this thread. My response has been stuck in the outbox for some time, so it seems sensible to post it here as well.
Colin, first the very short extract:
"The Fox with its tail is celebrated in song when the lark sings
Indeed the little voice of the farm animal is captured by speed, even the horse"
This obviously sounds a tad peculiar and may be some early misreporting.
The much longer section reads:
"And he was filled then with devising prophesies, composed as poetry, and made known over a period of ten years; such as:
'The Fox with its tail is wary, while the lark sings
Indeed the grasping farm animal is at the same time predated, even the horse'.
"The Fox with a tail" he called the Duke, who always had a fox's tail carried in his presence above his army.
"While the lark sings", he said of the one who in the morning was captivated by the song of the lark, just as he himself was captured; He who is taken and threatened as the sudden snatching of a farm animal, that is The Earl of Warwick; and of a horse - that is the Earl of Arundel; who either bore the sign of a bear, or a horse."
The reference here to a foxtail super hostem seems to indicate some kind of personal badge, standard or field-sign to indicate the Duke's position on the battlefield - not something worn by anyone.
Hope this helps
"Patres nostri et nos hanc insulam in brevi edomuimus in brevi nostris subdidimus legibus, nostris obsequiis mancipavimus" - Walter Espec 1138