What type of feathers assist marsh hawks in their hearing?

Facial disks are a specialized collection of contour feathers that are shaped in such a way as to aid in directional hearing. In the case of marsh hawks and many other raptors, these feathers frame their face and help funnel sounds towards their ears. The unique structure of facial disks allows for better sound localization, enabling the bird to pinpoint the location of prey or potential threats in its environment.

The other types of feathers don't serve this specific auditory function. Flight feathers are mainly responsible for aerodynamics during flight, while contour feathers give shape and insulation to the bird. Down feathers provide additional insulation but are not involved in hearing. Thus, facial disks are essential for enhancing the auditory capabilities of marsh hawks, making them more effective hunters.