The capercaillie is a very interesting bird. Here's a couple quotes from an old book of mine entitled Sport in Wildest Britian(1938) by H. Hesketh Prichard.
"Harvey Brown writes: "Of the occurrence of the Capercaillie in earlier historic times and prior to the extinction of the species in Scotland, there is not much to relate which has not been quoted"; but after stating that the bird was known to the ancient Britons as Ceiliog Coed, he goes on to assign Hector Boetius (1526) first mention of the species."
It would also seem that the birds were much desired for tablefare in the olden days, to wit:
"In Old. Stat. of Scot.XX.478, may be found the following letter written by James VI to the Earl of Tullibardine: James, Right trustie and right well-beloved cosen and counsellor, we greet thee well. Albeit our knowledge of your dutiful affection to the good of our service and your countrie's credite doeth sufficientlie persuade us that you will earnestlie endeavour yourself to express the same be all means in your power; yet there being some things in that behalf requisite, which seem not-withstanding of so meane moment as in that regaird, both you and others might neglect the same, if our love and care of our native Kingdom made Us not the more to trie their nature and necessity, and accordingly to give order for preparation of the every thing that may in any sort import the honour and credite thereof. Which consideration, and the known commoditie yee have to provide, Capercaillie and termigantis, have moved us very earnestlie to request you to employ both your oune paines and the travelles of your friendis for provision of each kind of the saide foules, to be now and then sent to us be way of present;............. The raritie of these foules will both make their estimation the more pretious, and confirm the good opinion conceaved of the good cheare to be had there.......... We bid you farewell.- At Whitehall, the 14th of Marche, 1617."
So it seems that the birds were considered rare some 400 years ago, and that they were considered good tablefare by King James and, later, others:
"Let us leave the old breed with a quotation from the Rev. L. Shaw, who goes more into detail concerning the caper than does any other early author; "Caperkylie (called also the Cock of the Wood); in Latin Capricalea, as if he infested the goats; but properly in Erse, Caper-coil-ie,- the Wood Horse, being the chief fowl in the woods. He resembles and is the size of a turkey-cock, of a dark grey, and red about the eyes; he lodges in bushy fir trees, and is very shy; but the hen, which is much less in size, lays her eggs in the heather, where they are destroyed by foxes and wild cats, and thereby the Caperkylie is become rare. His flesh is tender and delicious, though somewhat of a resinous and fir taste."
SRH