"Thunder as a bird is a continent-wide conception in North America, but nowhere as geographically portrayed as on the Northwest Coast, where he is found in monumental sculpture, masks, paintings, and every manifestation of art. And of all coastal artists, those of the Kwakiutl have embraced the thunderbird as a favored subject. Kwakiutl mythology abounds in references to this powerful tribe of birds. Thunderbird, or his brother Kolus, perches on memorial poles as a lineage crest, masked Tlasula dancers mimic his hunching stride, and his spreading feathers and arched beak glitter on button blankets. The Kwakiutl perceive the thunderbird as a giant eaglelike bird, horns or ears curling over the head, which often carries a whale or clutches the horns of the Sisiutl (cat. no. 132).
This Thunderbird mask is very simply and directly carved, with none of the deep modeling of features often seen in Kwakiutl sculpture. Instead, the planes of the eye, cheek and beak merge in a smoothly flowing surface on which the details are painted. Only the crescentlike nostril is carved. The green-painted eye socket, yellow beak, black eye detail and brow, and red lip and nostril are characteristic of Kwakiutl painting. A bold, white stripe painted over the eye socket green is a very striking but unusual accent, and probably a later addition.
Profuse hanging of shredded cedar bark partly dyed red and a rope of bark rimming the mask indicate its use in the Winter Ceremonial, called Tseyka by the Kwakiutl. Thunderbirds appear in several parts of this ritual complex, in which dancers dramatize the power acquired by ancestors in adventurous contact with supernatural beings. The mandible is hinged with leather straps and controlled by a cord run over a cross bar. Dancers, every day seeing eagles soaring, fishing, preening, strolling the beach, combine the natural bird's movements with a sense of the mythical bird's fabled power". – The Box of Daylight, Northwest Coast Indian Art, pg. 36