The hackle is in fact Tawny Owl

The silk is the old Pearsalls 6a, I have several old wooden spools of the stuff. The colour of the new stuff when you compare it to the old is actually not that bad. The modern Hot Orange is however hard to judge as I have a dozen spools of the stuff and there is a distinct colour change in them. This is probably due to a change in the dying process. Some of them seem to be pre decimalisation as the spool lengths are given in yards whilst others are given in metres.
On the fly, the herl head is tied in and wrapped first, then the hackle and finally the body is formed and the whip finish is behind the hackle. To flatten the bump from the whip finish behind the hackle I often untwist the silk so it lies flat and forms less bulk.