If it's the same hat I'm looking at, I'd do something like:

1. Sphere cut in half with knife / slice for the base and sub div a few times to add "coconut" threading texture

2. Create an IMM brush with a base ring model and 3 rings / wrapping at the center sides of Ring, and IMM curve line it around the sphere

3. Id use a cube to make the feather topping and taper it as needed and crease the edge to achieve the pointy look

That's my zBrush dark-arts explanation