I decided to use the cocoa thread in the light areas too. I kept going back and forth about using that or a light neutral and finally decided that the spines are mainly in the dark fabric so, dark thread would be best.
The feathers will go all the same direction around each circle and in the blocks that are between them the feathers will all end up going the opposite direction. Hard to explain but it will be apparent when I get to the next row (I did it on paper first!).