I've discovered I'm not very good at this 'take progress photos of work' thing. I got caught up in painting and didn't take any pictures until I was finished working.
Here is the finished mask. The long feathers are dyed rooster coque, and I stripped the edges off the other feathers to give them that 'teardrop' shape. You can see the back of the mask here, to show where I put sticky-backed felt to protect the face against friction from rough parts: