Filoplumes

Those tiny hair-like feathers with the forked ends on this plucked goose breast are filoplumes.

Most people know flight feathers, contour feathers and down feathers, but most birds also have these tiny hair-like feathers.

These specialized feathers are highly innervated at their base. Filoplumes are thought to be function monitoring feathers.

So they tell the bird if the associated normal feather is worn or not functioning properly.