https://en.wikipedia.org/wiki/%CA%BBAhu_%CA%BBula

Feather boas, feathers decorating Mardi Gras masks, peacock feathers in vases, ostrich feathers embellishing hats, but an entire cloak made of feathers? That was new to me. I had to investigate further.

Since Polynesia lacked precious metals or gemstones, the Polynesians came to treasure natural materials such as feathers. Featherwork garments were worn (usually with a feathered helmet) primarily by the chiefly castes, soldiers in battle, and for religious affairs.

The feathers came from a variety of birds. Birds caught specifically for their feathers were treated as a renewable resource, snared during the molting season, and released after harvesting to grow new plumage and to procreate.

On the other hand, meat breeds had their feathers removed after they were killed. Nowadays, due to economical and environmental issues (most of the birds became extinct), featherwork specialists often work with readily available feathers, dyeing and trimming the to shape.
https://commons.wikimedia.org/wiki/File:Memoirs_of_the_Bernice_Pauahi_Bishop_Museum_(1918)_(14586369068).jpg

Attaching feathers to form garments involves stretching a foundation cord between two wooden pegs, from which the artists suspend warp threads. They then twine weft threads around the warp threads, inserting feather quills within the twists of the twined threads, as they advance row by row.

A full sized cloak is made from hundreds of thousands of feathers and can take more than a year to complete.

Nowadays, featherwork cloaks and capes are mainly used in reenactments of traditional rituals and other formal occasions.

Resources

A Visual Guide to Traditional Techniques: World Textiles, by John Gillow and Bryan Sentence, Thames & Hudson.
World Textiles: A Concise History, by Mary Schoeser, Thames & Hudson.