What is the significance of this feathered helmet?

They were symbols of the highest ranking. Certain colored feathers were attributed more value than others. Since red was associated with gods and chiefs, red feathers were reserved for religious objects and garments worn by high-ranking members of society. In Hawaii, where the red-feathered i’iwi and apapane birds are small but plentiful, feathered capes made for the elite actually came to be known as ‘ahu ‘ula, meaning "red garment." The name did not change even after Hawaiian artists began including yellow feathers alongside the red. Rarer than red feathers in Hawaii, the golden feathers of the ‘o’o and mamo were highly prized.