sheath after 16-17 days of incubation results in the sheath not splitting as it should during the final stages of the feather's growth. Because of that abnormal splitting, the bird's down appears to be matted; chicks with this condition look bristly and singed and tend to be lighter in body weight than normal chicks are.

Human use

Down feathers are used by Indigenous North Americans for religious ceremonies and as powerful symbols. In the

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